EZNEC User Manual
EZNEC User Manual
Table Of Contents
Table Of Contents
EZNEC has a number of very powerful features for modifying groups of wires, located in the Wires Window Wires menu. There are also several powerful features in the Create menu, described in the Advanced Wire
EZNEC User Manual
Table Of Contents
EZNEC User Manual
MicroSmith ..........................................................................................130 winSMITH ...........................................................................................130
Third Party Software Legal Notices...........................................................137 vbAccelerator .........................................................................................137
Welcome to EZNEC
This manual has been written to cover all EZNEC program types, both standard and professional. Sections which don’t apply to all program types are identified; otherwise, all references in the manual to EZNEC apply equally to EZNEC+ and EZNEC pro programs EZNEC-M and EZNEC/4.
It’s assumed that you know basic Windows operation, such as clicking, dragging, and selecting, and references will occasionally be made to common
Windows tools such as Notepad or the Windows Explorer. Please consult your Windows documentation if you’re not familiar with basic Windows techniques.
Comments about this manual are always welcome and will be read, although a prompt personal reply might not always be practical. Please send comments and suggestions to [email protected]
Manual updates are included in the EZNEC maintenance releases which are
is a registered trademark of Roy W. Lewallen. All rights are reserved.
I want to give very special thanks to four people who, for a period of over a year, tested and commented on over 30 alpha program revisions as features were added, tested, and modified. Their effort was exceptional, and this version would not have been possible without them. They are:
L.B. Cebik, W4RNL
Dan Maguire, AC6LA
Dan Richardson, K6MHE
Dean Straw, N6BV
A great, heartfelt thank-you to these wonderful folks.
And many, many bugs were found, reported, and doggedly tracked down during the beta testing phase by the above people, plus beta testers:
Steve Best, VE9SRB
Dave Rodman, KN2M
Jim Streible, K4DLI
Bert Barry, VE3QAA
I’m indebted to all these people, for all their time, trouble, and valued comments, criticisms, and suggestions. They deserve a great deal of credit for
EZNEC 4.0’s better features; I take full responsibility for its shortcomings.
Although I’ve listed a call sign beside most of the testers’ names, several of them are also professionals actively involved in antenna design. Speaking of which. . .
This manual will be read by both professional and amateur users, so I’ll like to emphasize one point. Although amateur radio callsigns are listed for most of the fine people acknowledged below, many – in fact most – of them are highly experienced and regarded professionals in addition to being licensed amateurs. Please take a look at “
” for a little more about this topic.
Version 4.0 began as 3.0, and four people patiently reviewed the more than
30 “alpha” versions of EZNEC v. 3.0 as features were activated and debugged. They are:
Gary Breed, K9AY
L.B. Cebik, W4RNL
Ed Farmer, P.E., AA6ZM
Roger Steyaert, K7RXV
These gentlemen continued on to provide help and encouragement during the extended beta testing phase, and were joined by the following people:
John Devoldere, ON4UN; Linley Gumm, P.E., K7HFD; Rus Healy, K2UA;
Prof. Dr. Gerd Janzen, DF6SJ; Dick Kiefer, P.E., K0DK; Dean Straw, N6BV; and C.H. “Buck” Walter.
Many others offered to help test the program, and I thank them, but I was regrettably unable to constructively process the input from a larger group.
Valuable help in discovering and tracking down bugs after product release has been provided by Leland Scott, KC8LDO. Thanks also to others who have reported bugs, provided important information, and when necessary have downloaded and run diagnostic programs to help me find and fix them.
The fundamental computation portion of this program is that of NEC-2 and/or
NEC-4. Many people have contributed to the development of these codes, but in recent years the major contributors have been G.J. Burke and A.J. Poggio of Lawrence Livermore National Laboratory. Without their monumental effort this program would not be possible.
EZNEC v. 4.0 has evolved from earlier versions and from its predecessor
ELNEC, and the extensive help from the testers of earlier versions is instrumental in its success. These include:
Dr. Dick Adler, K3CXZ; Dr. Jack Belrose, VE2CV; Gary Breed, K9AY; Jim
Bromley, W5GYJ; John Brosnahan, W0UN; Paul Carr, P.E., N4PC; Dr. L.B.
Cebik, W4RNL; Dr. Al Christman, K3LC; Bill Clarke, WA4BLC; Tony DeBiasi,
K2SG; Ed Farmer, P.E., AA6ZM; Dick Gardner, N1AYW; Ernie Guerri,
W6MGI; Linley Gumm, P.E., K7HFD; Jerry Hall, K1TD; Ed Hanlon; Bob
Haviland, W4MB; Wes Hayward, W7ZOI; Dick Kiefer, P.E., K0DK; Doug
McGarrett, WA2SAY; Bob Rullman, K7MSH; Jim Sanford, WB4GCS; Roger
Steyaert, K7RXV; C.H. "Buck" Walter; and Dean Straw, N6BV.
I want to give special thanks to L.B. Cebik, W4RNL, who has consistently provided a tremendous amount of help during the development and testing of this and several previous versions.
Thanks to all the EZNEC users who took the time to send in their suggestions, and those who have patiently waited for this version. Finally, but foremost, thanks to my family for being understanding and supportive during the many, many hours I've spent away from them working on this program.
Acknowledgement and Special Thanks: Jordan Russell and Inno
All variations of EZNEC version 4.0.31 and later use the open source Inno
Setup installer, created by Jordan Russell. This is a tremendously rich and powerful but easy to use installer. I’m very grateful to the author and any other contributors who have obviously put in a tremendous amount of effort in developing this fine application and have made it available to be freely used at no charge. It wasn’t chosen for EZNEC because it’s free – it was chosen because it’s simply the best installer available, at any cost, for the job.
Acknowledgement: vbAcellerator Software
This product includes software developed by vbAccelerator
(http://vbaccelerator.com/). I thank vbAccelerator for generously making this high quality software available at no charge. The full license statement and disclaimer is in the Legal Notices section of this manual,
A Few Words About Copy Protection
A friend of mine made the observation that a conscience is kind of like a little wheel with sharp teeth that spins and digs into you. But each time it does, he said, the teeth wear down a little so the next time it's not quite as sharp.
Eventually, if you use it enough, there aren't any teeth left. If the teeth on your wheel are worn all the way down, what I'm about to say won't reach you anyway so you may as well skip the rest of this section.
EZNEC User Manual
Copy protection is a big nuisance to both the user and the software developer.
It also can necessitate an increase in price. That's a lousy deal -- more nuisance for a higher price. That's why this software is not copy protected. Yet copying it is easier than ripping off a Walkman from K-Mart, with zero chance of getting caught (although it's just as illegal and dishonest). So it's pretty risky to put the product out without copy protection. I'm well aware that sellers of similar programs have had to copy- protect their programs to prevent such theft. Theft? You bet! Over a year of virtually full-time work have gone into developing just this version of this program and refining it to make it useful and easy for you to use, and over two years for the first Windows version.
(Other expenses, like advertising, aren't cheap either!) So please, when someone asks you for a copy of the program, realize that he or she is asking you to steal. Politely say no, but tell them where they can order a copy
). It's a bargain at the price, it'll save future users more nuisance and a higher price, and it'll save the wear on your conscience wheel.
This software is protected by a hardware key. Every effort has been made to make the protection system as reliable and easily usable as possible. It not only protects the developer from theft of software which has taken literally thousands of hours to develop, but also protects you, the user, from having to compete with those who might otherwise use the same tools without having paid for them.
All comments about this copy protection method, both positive and negative, are solicited and welcome.
If you’re not completely satisfied with EZNEC, I’ll promptly refund the full purchase price. There is no time limit to this guarantee for the standard and plus programs, and it’s good for 90 days after the purchase of EZNEC pro.
Amateur or Professional?
Past versions of EZNEC and EZNEC pro have had separate manuals.
Besides the obvious difference of EZNEC pro’s additional features, the manuals were written with a bit different orientation, with an eye toward the most likely level of technical expertise of their respective users. With this version the manuals have been combined. Because maintaining two separate manuals involves a great deal of extra time, combining them frees that time to be put to use in improving the program itself.
Even the standard EZNEC program has an extremely diverse user base. It’s purchased and used by amateurs who have very little technical background in electrical fundamentals, let alone electromagnetics or antenna design. It’s also used by the U.S. and foreign military services, aerospace companies, defense contractors, international broadcasters, universities, and so forth. Add to that the EZNEC pro users, and you have an idea of the enormous range of background knowledge represented by the readers of this manual.
So please, for those of you who are more knowledgeable, don’t be insulted if some concepts are explained more simply than you’re accustomed to. And for those with less experience, don’t think for a minute that an effort is being made to snow you. The sole objective here is to communicate, and give you the information you need to get the most from EZNEC, whichever program type you’re using.
The only relevant question is whether you get from this manual the information you need. If I fail to communicate, the fault is mine, and I’d like very much to hear where I failed. With today’s tools it’s not difficult to modify the manual, and your input will help improve it and make it more useful to others. So please let me know when you run across problems with the manual. I apologize in advance for not always being able to respond personally and promptly. But your comments will be read, and they will be acted upon. Please send your comments to [email protected]
I’m sometimes asked if there are any restrictions on professional use of the standard program. No, there are none at all, and in fact it’s widely used for a wide variety of professional purposes. The distinction between program types is only in price and features, not in how they’re used. The other side of that coin is that people wanting to use the professional version for strictly amateur purposes pay the same price for the professional version as everyone else.
The only use restriction on any program is that only one person can use the program at one time unless corresponding additional copies are purchased.
Like many, many EZNEC and EZNEC pro users, I also wear two hats, so welcome to both amateur and professional customers. I’m one of you both.
Roy Lewallen, P.E., W7EL
Notes For International Users
It is my intent to make EZNEC work correctly on computers set for the standards of other countries. This means that if a comma (,) is set as the decimal separator by the Windows Control Panel Regional Settings, all numbers should be displayed with that convention, and all numerical inputs are designed to accept that convention. (The decimal separator is automatically chosen according to your language preference. However, it can be changed to another character via the Regional Settings if desired.) You must use this separator when entering numbers into EZNEC. (There are a few exceptions to this, detailed below.) Dates should be displayed according to your standard. All outputs should print correctly on A4 as well as U.S. sized paper, and the program should otherwise operate normally in all respects. If you encounter any operation, at any time, which requires you to enter or view data in a format other than the standard convention for your country, please let me know. Of course, all details you provide will be helpful.
EZNEC is unable to correctly format numbers when run on some operating systems if the both the decimal and thousands separators are set to characters which aren’t standard for the region of operation. If the setting causes a problem, EZNEC will detect it and show an error message when the program starts.
A period (.) is used as the decimal separator in all comma-delimited output
. Comma-delimited output files are intended to be used
EZNEC User Manual for importing data into spreadsheets and other such programs. In this format, fields are separated with commas, so the period must be used for decimals.
EZNEC pro only: NEC-format files read and written by EZNEC-M and
EZNEC/4 use the U.S. standard, because I believe that most compiled versions of NEC-2 and NEC-4 expect and produce files using this convention.
Please let me know if you have any information to the contrary, or if you see any indication that EZNEC is not producing or interpreting these files with U.S. conventions.
Thousands separators are not used in EZNEC. However, certain settings of this option can cause a problem. See the first paragraph in the Exceptions section.
What's New in v. 4.0
This topic describes the differences between v. 4.0 and the previous Windows version, 3.0. If you’ve just upgraded from ELNEC or a DOS version of
EZNEC, please read instead the
chapter in the
Upgrading from DOS EZNEC or EZNEC pro section.
Control Center Menus
The Plot menu no longer exists. Its functions have been moved to the Desc
. The Information
Window now contains all the choices which are saved with the description file, except for the near field and frequency sweep setups, which remain in the
Control Center Setups menu.
The new EZNEC+ program type permits 1500 segments. The EZNEC pro program types (EZNEC-M and EZNEC/4) now allow 20,000. Note, however, that files as large as 6 GB can be written for the largest possible pro models at double precision, and calculation times can run to more than a day with 2
Segmentation Check (formerly Guideline Check)
to reduce confusion with the new Geometry Check (below). As before, the
Segmentation Check is only run when opening a file and under a few other conditions, and its results won't inhibit calculations. It now takes into account the velocity factor when evaluating buried wires (EZNEC/4 only), which can result in warnings in descriptions which didn't formerly generate any.
EZNEC v. 3.0 has a Guideline Check feature to check the model against modeling guidelines for segment length. In EZNEC v. 4.0, this has been
feature has been added. This powerful feature, run automatically before each calculation, checks the model for errors such as wires crossing at other than a wire end or segment junction, wires occupying the same space or overlapping, or wires coming too close to each other.
Wires Window Features
There are a number of new, powerful features in the Wires Window Wire
, Copy Wires (which allows making offset copies), and
. These can be used with a group of selected wires, or with a sequential group of wires selected after choosing the action to perform. There’s a new Create menu, with the familiar
EZNEC User Manual
Create Radials and, for EZNEC pro users, Create Wire Grid. Check out the
Loop Size should be of particular interest to quad designers, although they’re useful for many other applications.
The new "Rotate Wires" feature shouldn’t be confused with the Elevation
Rotate End and Azimuth Rotate End features accessed by right-clicking a wire end cell – present in both v. 3.0 and 4.0. The new feature allows rotating any group of wires around any axis, around the end or center of any wire, or around any point in space, while the right-click feature rotates a single wire around one of its ends.
View Antenna Display
The display can now be moved by dragging while holding down the right mouse button, and zoomed by dragging while holding down both buttons. See
. Because of the new use of the right mouse button, the Wire Information popup window appears when you pause the cursor over a wire. This behavior can be changed via the WireInfoDist
Circular Polarization (plus and pro only)
There are several new 2D and 3D plot, and Far Field Table display options: right and left circular polarization, and linear component along the major and minor axis of an elliptically polarized field. These are selected via the new
Desc Options line in the main Control Center window. Click Desc Options, then select the Plot tab, then the Fields tab. Note that the selection affects the
2D and 3D plots and the FF Table.
Major enhancements have been made to the
multiple fields (e.g., Total, Vertical, and Horizontal), you can click on the field name in the list at the left of the display, and the cursor will move to that field.
The data in the data window will reflect the values for that field. When you add saved traces to the display, you can view only one field at a time, selected via the Mult Trc Fld choice in the 2D plot window View menu. There, you can choose among the fields selected in the main window Desc Options dialog box for the normal 2D display. If you add traces to the display, clicking on the name of any added trace file at the left of the display will move the cursor to that trace, and the data in the data window will reflect the value for that trace.
Also, an extra line will appear in the right column of the data window, giving the field strength of the selected trace relative to the primary trace at the cursor angle.
The minimum step size for the 3D plot is now 1 degree instead of 2.
There's now a fully double-precision NEC-2 engine choice (plus and pro only),
faster than before, most notably in the calculation of currents. The amount of speed improvement depends on which engine you've selected, what portion of the total calculation time is needed for the calculation of currents, and the
Getting Started type of CPU you have. But it can be quite spectacular with the NEC-2 engines, in particular. In program types allowing a choice of more than one calculating engine, the choice is shown just above the FF Plot button in the
EZNEC v. 4.0 has the capability of including the effect of wire insulation. See
topic for more information.
If you chose other than the default printer in EZNEC 3.0, your choice would become the system default printer. Also, many printer property choices were ignored by EZNEC 3.0. These deficiencies have been corrected.
Easy Import of Wire Coordinates from NEC Files (EZNEC+, EZNEC pro only)
An additional format is allowed for importing wire coordinates from an ASCII file: the NEC GW “card” format. See the Wire Coordinate File topic for more information. This is the “second format” discussed in that topic.
Multiple Instances (EZNEC pro only)
Multiple instances are permitted in the pro programs, including doing simultaneous calculations. The instance number is identified by a number in parentheses in the title bar of each window. (EZNEC/4 only): An external
NEC-4 program can be run only from the first instance.
Multiple Instances -- EZNEC 3.0 permitted multiple instances to be operating at the same time, provided that calculations weren’t run. Because of the way certain new features were implemented, the v. 4.0 standard and plus program types don’t allow more than one copy to run at once.
Ground -- The Real, Fast (reflection coefficient) ground type is no longer available. With today's machines, the saving in calculation time over the High-
Accuracy (Sommerfeld) ground isn't significant, and the Fast option is limited in accuracy with low antennas. Description files with Fast ground specified are converted to High Accuracy when opening, and will be saved with High
Loads -- When you convert from R + jX to RLC type loads (either directly or due to combining descriptions with different load types), you now have the option of conversion to a parallel RL or RC equivalent.
Wire Connections -- Wire end coordinates will always be modified to be identical if the wire ends are deemed connected (same coordinates within about 1/1000 segment length), because NEC always does this. It was formerly an option (Options menu Auto Coord Match), but no longer is.
LastZ.txt – (EZNEC pro only): LastZ.txt files for instances beyond the first will persist in the EZW program directory as LastZ_N.txt, where N is the instance number. The file for the first instance will still be simply LastZ.txt.
EZNEC User Manual
Messages -- The tooltips can now be turned off, as well as the new message warning you if the description has changed before opening a new description, via Messages On/Off in the Options menu.
Crash Recovery -- A feature that I hope won’t see much use. . . if you should
program you’ll get a prompt giving you the opportunity to recover to the model as it was just before the crash.
Ground Wave Analysis -- (EZNEC pro only): Ground wave analysis can produce somewhat different phase angles for the polarization components than earlier versions, particularly when the observation point is many wavelengths from the origin. The cause is some slight changes in internal constants. The calculation of the phase at many wavelengths is sensitive to very small changes in these values. However, the important thing is the relative phases of the components, which remain very close to the same as in previous versions.
NEC Format Files -- (EZNEC pro only): EZNEC pro v. 4.0 can read GH
(helix) and IS (wire insulation) “cards”. EZNEC pro will accept a file if it contains at least one GW, GH, or GA “card” in addition to a source. New
Special Option choice LD5Translation = First will cause EZNEC pro to apply the wire loss parameters of the first LD5 “card” read as global Wire Loss, and ignore additional LD5 “cards”.
If You Downloaded EZNEC
If you downloaded EZNEC, it came in the form of one file. Please back this
up. Major changes to your computer system might necessitate a reinstallation of the program, and you’ll need this file to do it. And a virus or hard drive crash can corrupt or delete the file. If you aren’t able to back up the file, please contact me to purchase the CD-ROM. The cost is nominal for people who have purchased the download. Updates (maintenance releases) will be available from time to time, and you should also keep the most recently
Getting Acquainted with EZNEC
. This leads you through some of the basic operations. After the Test Drive, you’ll be ready to model simple antennas. Then as you progress and want to learn more, begin reading the
chapter. For detailed information about a window or menu, look in the Reference chapter. And, as you use
EZNEC, press the F1 key when you have a question about a particular menu, control, or display. It’s not possible to cover all menus, controls, and displays, but many of the important ones or ones particularly needing explanation do have links. If a link isn’t present, the manual will open to an introductory section.
The EZNEC manual might seem long and complex. This isn’t because
EZNEC is hard to use or learn, but because it has a rich set of features, and every effort has been made to explain them as thoroughly as possible.
I’m sure you’ll find EZNEC to be a valuable and educational tool.
Making a Desktop Shortcut
When you install EZNEC on your machine, you’ll get the option of creating a desktop shortcut. If you decline, you can still make one manually at any later time.
Here’s how to make a shortcut to EZNEC on your desktop. The precise wording might vary slightly from one operating system to the other.
Right-click the Start button at the lower left of your Windows desktop. From the menu, chose “Explore” to open Windows Explorer. Navigate to the
EZNEC program file directory (folder). If you selected the default directory during installation, this will be C:\Program Files\EZW. Otherwise, it will be whatever you specified at installation time.
In the EZNEC program file directory, locate the file EZW.exe (standard or plus program), EZWpro.exe (pro programs), or EZWDemo40.exe (demo program).
(You might not see the .exe part, depending on how you have Windows set up.)
Right-click the appropriate .exe file and select “Send To” from the menu. From the next menu, select “Desktop (create shortcut)”. You’ll probably see a message telling you that, sure enough, Windows is going to do what you asked it to. When you click “Ok”, the shortcut will be placed on your desktop.
You can rename it if you like. Double-clicking it will start EZNEC.
The program will open with a description file of your choice if you put its name on the command line in the shortcut properties, or when starting EZNEC from
Windows Start/Run. Note that the path\EZW.exe combination or the file name has to be enclosed with quotation marks if either contains a space.
You can also start EZNEC by dragging an EZNEC description (.EZ) file to the shortcut and dropping it.
EZNEC Pro Users
chapter of the Reference section under Additional Information.
Printing The Manual
Nearly all Windows software currently being sold uses a help system for a manual, as EZNEC does. I personally disliked help systems for some time, but after getting used to using them, have come to greatly prefer them to printed manuals. Among the advantages are the hyperlinks, or jumps, allowing instant movement between topics, and extensive indexing.
However, many requests have been received from EZNEC users for a printed or printable manual. So a printable manual has been made available for those who want one. If you purchased EZNEC 4.0 on a CD, you’ll find the printable manual in the Printable Manual directory of the CD. The Readme.txt file in that directory contains information and instructions. If you don’t have a CD, you can download the printable manual from http://eznec.com/ez40manual.htm
. The manual is for use only by EZNEC customers and EZNEC demo users.
The printed manual is generated from the help file by the software used to develop the help file. The conversion process may have some imperfections,
EZNEC User Manual so the resulting format isn’t flawless. However, because the on-line help system is intended to be the primary manual for EZNEC, and any formatting changes would have to be repeated each time the manual is updated, comprehensive editing and correction of minor formatting flaws in the printable manual won’t be undertaken. The user can make any changes deemed necessary to the Microsoft Word version.
Test Drive Introduction
The best way to get familiar with EZNEC is to take it for a spin. Let's analyze a
20-meter dipole hung 30 feet up in the back yard. If you've started EZNEC, you should see the Control Center. The file Dipole1.ez is included with the program and should be installed at the proper location, so we'll start with that antenna and modify it as necessary.
Notes: <Enter> means the Enter key, <ESC> is the Escape key. You can type any entry in uppercase, lowercase, or any combination. When text to be typed is surrounded by single or double quotation marks, don't type the quotation marks themselves.
Along The Straightaway
This exercise leads you through the creation of a simple dipole, and illustrates some of the basic steps in creating an EZNEC model. Most of the steps could be done in any order. The order of steps in this exercise is pretty much arbitrary. If you’d like to take a break before finishing the tutorial, you can simply end EZNEC by selecting Exit from the Control Center File menu, and the next time you start EZNEC, it will resume where you left off. Or you can save the description by selecting Save Description As from the File menu, or by clicking the Save As
can open the description by selecting Open from the File menu, or clicking the
Open action button, and specifying the name you used for saving.
In the Control Center, locate the Open
a file selection dialog box. Select Dipole1.ez, or enter ‘dipole1’ in the “File name” text box and click Open. Click here if you have trouble.
The bar at the top of the Control Center
should now read
"Dipole in free space" -- this is the title of the antenna description stored in file
Dipole1. Let's enter a title for our back yard dipole.
Click anywhere on the information window title bar (where the text
“Dipole in free space” is), and a dialog box will open for you to enter the new name. Enter ‘Back yard dipole’, then click Ok or press the <Enter> key. Notice that the information window title bar now shows the new description name.
Now let's change the frequency to 14 MHz --
Click anywhere on the Frequency information window line, or on the
to its left. Enter ‘14’ in the dialog text box, and click Ok or press <Enter>.
Let's choose feet for a convenient unit of measure. (This isn’t the most convenient for international users, but please select feet for this example.)
Click on the Units line or the selection button to its left, then select
Feet, and Ok.
The ground type for model Dipole1 is Free Space, and we’ll want to model this antenna over ground. This will be taken care of after we define the wires and sources.
EZNEC User Manual
Next we'll describe the antenna itself. EZNEC gives you the ability to see the modifications you’re making as you make them. To take advantage of this powerful feature, open the View Antenna window by clicking the View Ant action button in the Control Center.
In the View Antenna Window, click to open the View menu. If a checkmark appears next to Show
Controls, click Show Controls to turn the control box off. Repeat for
Show Data if it’s also checked.
This turns off the control and data boxes, which aren’t needed now. Next, open the Wires Window by clicking on the Control Center “Wires” line, or the selection button to its left. Position the Wires and View Antenna
Windows for convenient viewing. You can resize the View Antenna
Window if desired by dragging a side or corner. It’s ok to cover all or part of the Control Center for the time being.
The Wires Window is where the wires of the antenna are actually defined. The position of each wire in space is specified by giving its x, y, and z coordinates.
These coordinates represent distances from the origin. For example, look at the numbers in the Wires Window for Dipole1. It consists of one wire which extends along the y axis. The y coordinate of End 1 is about –0.82 feet, and the y coordinate of End 2 is about +0.82 feet, so the wire is about 1.64 feet long. You can confirm this by moving the mouse cursor to the y-axis line in the
View Antenna display (where the wire is – it might be a little hard to see at the moment) and leaving it still for a moment to open the Wire Information window. Alternatively, you can move put the mouse cursor over the selection button at the very left of Wire 1 in the Wires Window and right-click it.
Dipole1 is a half wavelength long at about 300 MHz, so it’s much too short for our 20 meter dipole. Let’s make the wire the length we want.
Assuming our back yard dipole was designed using 468/f(MHz) to determine the length, the length is 33.43 feet. EZNEC doesn't require any symmetry, and we’re free to choose where in space we put the origin (except that it has to be at z = 0 if a ground is used) so for convenience we'll put one end of the wire at x,y = 0, 0 and the other at x,y = 0, 33.43. Placing it along the y axis makes the maximum lobes in the direction of the x axis. Ground is always defined as being at z = 0 (for the innermost medium). Since the antenna is horizontal and up 30 feet, the z coordinate of both ends is 30. To enter the coordinates,
Click on the Wires Window cell for Wire No. 1, End 1, Y (where the current value is –0.82…), and change the value to 0.
Notice that the mark on the button at the left has changed to a pencil. This indicates that the row (wire) has been edited. Note also that the number you’ve entered is shown in red. This indicates an edited value. The edited value won’t be accepted by EZNEC until you click on another row of the grid, move the insertion point off the row with the <Tab> or arrow keys, or press
<Enter>. You can undo an edited value, but only before it has been accepted, by pressing <Esc>. Pressing <Esc> again will undo all edited values in the row.
Move to the next cell (End 1 Z) with the mouse or <Tab> key and enter
The coordinates of End 1 are now 0, 0, 30.
Similarly, modify the End 2 coordinates to be 0, 33.43, 30.
Finally, define the wire diameter. We’ll assume the antenna will be made from
12 gauge (AWG) wire.
In the “Diameter” column, enter ‘#12’. (EZNEC will also accept the diameter in inches, or other appropriate units depending on the Control
Center Units selection.)
The last column is to define the number of segments for the wire. 11 is a reasonable number for pattern analysis of a half-wave antenna, so we don't need to change it. (We do need an odd number of segments so we can put our source in the middle of the wire.)
Then press <Enter> so EZNEC will accept the values.
Notice that the View Antenna display has changed to show what the new antenna looks like. You should see a horizontal wire parallel to, but above, the y axis. If you don’t, go back to the Wires Window and correct the coordinates.
End 1 coordinates should be x, y, z = 0, 0, 30, and End 2 coordinates should be 0, 33.43, 30.
Move the mouse cursor to the wire in the View Antenna display, and leave it still for a moment to open the Wire Information window. The length of the wire should be 33.43 feet. If it isn’t, correct the coordinates in the Wires Window.
The next step is to define the source. This is connected at the point where the power is applied to the real antenna, in this case the center of the wire.
Close the Wires Window by clicking the close button in the upper right corner (the small box with the “X” mark).
Open the Sources Window by clicking on the Sources line in the
Control Center information window, or on the selection button to its left.
In the Sources Window grid, you can see that there’s one source (source no.
1), which is placed on wire #1, 50% from end 1. This is where we want the source to be. However, this is a good time to practice a little with the Sources
In the Sources Window, locate the cell in the % From E1 column in the
Specified Pos. group. Change the value from 50 to 25 and press
This change had several effects. First, the value shown in the % From E1 column in the Actual Pos. group changed from 50 to 22.7273. When you specify a source (or load or transmission line) position, EZNEC attempts to place it as close as it can to the specified position. But it’s restricted to placing the source in the center of a segment. (In reality, the source excitation is spread over the whole segment, but it’s easier to visualize as being at a single point.) So EZNEC tells you, in the Actual Pos. group, where the source is actually placed. So the Actual Pos. group columns show that the source is
22.7+ percent from end 1 of the wire, and it’s on the third segment from end 1.
You can see this placement in the View Antenna display. (You can maximize the display by clicking the maximize button -- the one with a square -- near the upper right corner, for better viewing, then return it to normal size by clicking the same button again. Segment junctions are shown as dots on the wire.)
The benefit to specifying source, load, and transmission line positions in terms of percent from the wire end is that the wire length or number of segments can be changed without affecting the relative position of the source (except as necessary to place it at a segment center).
EZNEC User Manual
The source type, shown in the Type column, is a current source. The Sources
Window also show the source amplitude and phase, in this case one ampere at zero degrees. When a model contains only a single source, the magnitude, phase, or type have no effect on the pattern or source impedance. So we’ll leave these as they are for now.
Now restore the source to the correct position in the middle of the wire.
Change the value in the % From End 1 column of the Specified Pos. group from 25 to 50, then pressing <Enter>.
The source should now appear in the middle of the wire in the View Antenna display, and the Actual Pos. should now show as 50 percent, on segment 6.
The source could have been connected through a transmission line. However, this will affect only the impedance seen by the source. It will have no effect on the antenna gain, pattern, or other characteristics. No transmission line will be used in this example.
Close the Sources Window by clicking the close button in the upper right corner.
Now it’s time to deal with the ground. Presuming you don't have a perfect ground plane in your back yard (and for many wavelengths in all directions), you'll want to do the analysis over "real" ground.
Click on the Ground Type line, and select Real.
The height of the antenna will determine which ground model we use. If you have a fast computer, you can always choose High Accuracy analysis unless you need to make a connection to ground. Let's choose MININEC type ground for now. That model is good with horizontal wires which are at least 0.2 wavelength high, and it's fast.
Choose MININEC, then Ok.
Finally, we need to specify the ground characteristics.
Click on the Ground Descrip line. This opens the Media Window.
Note that the Ground Descrip selection isn’t visible unless Ground Type is
Real. The Media Window is where specification of Real ground is done. One or two ground media can be specified, but we’ll only need one for this model.
When we changed the ground type to Real, one ground medium was created.
The conductivity and dielectric constant of newly-created grounds can be set for your local ground conditions by means of the
Default Ground Const selection. The values initially used by EZNEC are those of “average” or “good” ground (conductivity of 0.005 S/m, dielectric constant of
13). These are the values you should see in the Media Window at this point, unless you’ve changed the default ground constants.
For this exercise, let’s suppose your back yard has the characteristics of “very good” ground.
Move the mouse cursor to either the Cond. or Diel. Const. cell in the
Medium No. 1 row, and click the right mouse button. Note: Make sure the mouse cursor, not just the text insertion point, is in the designated cell when you right-click.
This will open the Ground Characteristics dialog box.
Select the Very Good option, then click Ok.
The Media Window should show 0.0303 for the conductivity, and 20 for the dielectric constant.
Close the Media Window by clicking the close box in the upper right hand corner.
This completes creation of the model itself. We can now choose what to calculate and display. Note that all the information in the Control Center
is saved with the description when the description is saved to a file. In addition, frequency sweep and near field analysis setups, and the selections in the Control Center Plot menu, are saved in this file.
We know that the dipole's maximum lobe will be at zero degrees, but at what angle above the horizon will it be maximum? We'll run an elevation plot to find out. (3D plotting is covered in "On The Race Course", in the last section of the
Click on the Plot Type row in the Control Center.
This opens the Plot Type dialog box.
Select Elevation, then Ok.
The azimuth angle for the plot is zero degrees (broadside to the antenna), which is where we'd like to look, and all the other parameters look fine. To plot the pattern,
This tells EZNEC to compute and display the 2D far field pattern. You’ll briefly see the
while the calculation is running. When it’s finished, you should see the plot and some text below it with information about the pattern.
If you don’t see the text below the plot, open the 2D Plot Window View menu, and select Show Data.
The plot represents an elevation “slice” of the antenna pattern. From the text in the data box, you can see that the pattern is maximum at 34 degrees above the horizon, and other information about the pattern. You can see the antenna gain (second row in the data box, on the right) at any elevation angle by moving the cursor. This can be done by simply clicking on the 2D plot. The cursor will move to a point on the plot which is on an imaginary line from the plot center to the mouse cursor location. Note that the mouse cursor must be in the plot window when the button is initially pressed, although it can be moved outside the window while being held down. You can also press and hold the left mouse button and drag the cursor to the desired angle. The cursor can also be moved with the arrow keys (for fine steps) or the <Page
Up> and <Page Down> keys (for coarser steps). Before using the arrow keys, you should click on the 2D plot window. Otherwise, they might adjust some other program parameter or control.
Click the Src Dat action button in the Control Center.
This gives you information about the source. The fact that the impedance of
79.16 - j 45.11 ohms has a negative reactive part indicates that the antenna is operating below resonance and needs to be lengthened if resonance is important. The formula of 468/f (MHz) feet is an approximation, and the exact resonant length depends on the wire diameter and height above ground. The
Source Data display also shows that if a 50 ohm transmission line were connected to this antenna, the SWR on the line would be about 2.3:1. If a 75 ohm line is used, the SWR on the feedline would be about 1.8:1.
Close the Source Data display by clicking the close box.
In the View Antenna display, an additional line has appeared, above the antenna wire. This indicates, by the distance of the line from the wire, the magnitude of the current along the wire. You can see that the current is maximum at the antenna center and tapers to zero at the ends. The current
EZNEC User Manual indication appears only after calculations have been done, and it can be removed from the display if desired.
In the 2D Plot Window, open the File menu and select Save Trace As.
Enter the name “Back Yard Dipole”, and click Save.
This saves the 2D plot (trace) in a file named Back Yard Dipole.pf. We’ll use it in the next exercise.
Save the antenna description by clicking the Save As action button, entering the name ‘Back Yard Dipole’, then clicking Save.
This concludes the drive down the straightaway. If you’d like to try your hand
You can continue directly from here, or you can exit EZNEC and do the next exercise later.
Through The Curves
If you haven’t yet done so, take EZNEC “
”. In this section you’ll begin with the plot generated by the “straightaway” drive and get introduced to a few of EZNEC’s more advanced features. Ready to go? Let’s see how an inverted vee compares with our back yard dipole.
If you’ve shut down EZNEC since doing the “along the straightaway” exercise, you’ll have to open the back yard dipole description after starting EZNEC.
This is done by clicking the Control Center Open action button, entering the name ‘Back Yard Dipole’, and clicking Open. You should also open the View
Antenna window by clicking the View Ant action button.
Open the Wires Window by clicking on the Wires line of the Control
Center information window.
We’ll make the inverted vee by beginning with a dipole, then use one of
EZNEC’s powerful editing features to convert it into an inverted vee without having to calculate any additional wire end coordinates.
An inverted vee can’t be made from just one wire since it’s bent in the middle and all wires must be straight. So we’ll have to add another wire and use each of the two wires for half of the inverted vee. Let’s put the center of the antenna at x, y, z = 0, 0, 30 (30 feet straight up from the origin). Note that end 1 of wire
1 is already at this point, but we’ll need to modify its length to be suitable for the new antenna. To make the new inverted vee the same length as the original dipole, each of the two wires should be 16.715 feet long. So first we’ll modify the existing wire to be this length. Watch the View Antenna display when you press <Enter> in the following step.
Change the End 2 Y coordinate to 16.715 and press <Enter> to make
EZNEC accept the new value.
If you watched the View Antenna display when you pressed <Enter>, you saw that the wire appeared to change both its length and height above ground.
The height, however, didn’t really change. The reason for the apparent change is that EZNEC rescales the View Antenna display each time you change a wire, making it as large as possible without going beyond the window boundaries. Although the relative dimensions of everything on the display are correct, you can’t determine absolute values from this display.
Notice that in the display, the height of the wire is a little less than twice its length, which is the correct proportion.
The coordinates of Wire 1 should now be 0, 0, 30 (end 1) and 0, 16.715, 30
(end 2). If not, manually correct them and press <Enter>.
Now we’ll add the second wire. A wire can be added at least two ways. The simplest way to add a single wire is to simply type its coordinates and other parameters on the add row, identified by the asterisk (*) on the button to its left. In this step, you’ll also learn how to use one of EZNEC’s powerful editing shortcuts.
Position the mouse cursor over any of the cells of End 1 of the add row and click the right mouse button.
This opens the list of shortcuts.
Select Connect End to. In the dialog box, enter the value 1 in each of the two boxes.
This tells EZNEC that you want to connect this end (end 1) of the current wire
(the new wire) to end 1 of wire 1.
Click Ok or press <Enter>.
There should now be two wires shown in the grid, numbered 1 and 2. The coordinates of end 1 of wire 2 are the same as the coordinates of end 1 of wire 1, as a result of the last step. Take a look at the column labeled Conn.
(Connections) in the End 1 group. This shows which wire and end is connected to an end. In the wire 1, end 1 Connections column, you should see “W2E1”. This tells you that wire 1, end 1 is connected to wire 2, end 1.
Likewise, the entry in the wire 2, end 1 column shows the connection to wire
1, end 1 as “W1E1”. In this example, the connection is pretty obvious, since the coordinates of the two ends are right above and below each other. But you’ll find this feature handy with more complex antennas. If more than one wire is connected to an end, only one connection will be shown in the
Connections column, but by following the connections you can identify all the wires connected together.
There are a couple of other things to point out about the new wire (wire 2).
Notice that it’s the same diameter as wire 1, and has the same number of segments. By default, EZNEC gives a new wire the same diameter and number of segments as the preceding wire. It will, of course, use other values you specify if you do specify them.
In the View Antenna display, you can see the new wire you’ve created, although it might not be too obvious. It extends from one end of the horizontal wire (wire 1) to the origin, right along the z axis. If you don’t see the numbers beside the wires, select Objects from the View Antenna display View menu, and check the Wire Numbers box, then Ok.
End 2 of the new wire is at the default coordinates of 0, 0, 0. When a ground is specified (as it is here), a z coordinate of zero automatically means a connection to ground. This shows in the Wires Window Wire 2 End 2
Connection column as “Ground”. Now it’s time to fix end 2 of wire 2.
Change the wire 2, end 2 coordinates to 0, -16.715, 30, and press
Notice in the View Antenna display the effect this change has on the antenna.
Wire 2 now looks like an extension to wire 1.
We could have reversed the ends of wire 2 with no effect on the overall result.
The choice of which end to call end 1 and which to call end 2 is pretty much arbitrary. One thing to keep in mind, however, is that reversing the ends causes a reversal in the direction of current which EZNEC reports. So when multiple sources are used, or where the currents are of interest, it’s wise to be systematic in assigning the end numbers. For example, in an array of phased
EZNEC User Manual vertical antennas, you should face all end 1s the same way, so all element currents will be defined as flowing in the same direction. For this antenna, though, the choice of end 1 makes no practical difference.
Our new antenna has twice as many segments as the back yard dipole. This is fine unless you’re using the EZNEC demo program, which is limited to 20 segments. If you are using the demo, change the number of segments on
both wires to 10 before proceeding.
Close the Wires Window.
You can see in the View Antenna display that the source (represented by the circle) is still on wire 1. To make a dipole or inverted vee from the two wires, the source has to be at the junction of the two wires. However, the NEC calculating engine used by EZNEC spreads the source excitation over a whole segment (or, conceptually, places it at a segment center). We don’t have a segment center at the center of the antenna, so what should we do?
One solution to this problem is to insert a third wire between the two and put the source on it. However, this can be trickier than it seems, because of
NEC’s general fussiness about
. The best solution is to make use of EZNEC’s split sources, which can be placed at a wire junction.
Please click the link for more information about them.
Open the Sources Window by clicking the Sources line in the Control
Center information window. Click the cell in the Source 1 Type column.
As soon as you click the cell, a small button with an arrow appears in the cell.
This indicates that several distinct choices are available. Clicking on the button opens a pull-down list of choices.
Select ‘SI’. Then move to the % From E1 column in the Specified Pos. group and change the value from 50 to 0.
This will put a split current source at end 1 of wire 1.
Press the <Enter> key.
On the View Antenna display, you should now see two source circles, one on each side of the wire 1 – wire 2 junction. You can rotate the display for better viewing by pressing the left mouse button while the cursor is in the display window, then moving the mouse while holding the button down. You can also resize the display by dragging any of the sides of the window.
At this point, we have a dipole again, but made from two wires instead of one.
Click the FF Plot action button to generate a 2D plot. In the 2D Plot window, open the File menu and select Add Trace. If you saved the trace from the “Along the Straightaway” exercise, you should see a file named “Back Yard Dipole”. Click it, then click Open.
This overlays the back yard dipole plot with the plot from the new dipole. It should overlay exactly, showing that the new dipole, made with two wires and a split source, and centered with respect to the x axis, has the same pattern as the single wire, offset dipole with a standard source. This illustrates that you have a great deal of flexibility in modeling your antenna.
Click the Src Dat Control Center action button.
The indicated impedance is slightly different than it was for the original dipole.
Most of the difference is due to the fact that the new dipole has twice the number of segments. But small differences in reported impedance are to be expected whenever a model is changed, however slightly. The differences are insignificant for any practical purpose. If you’d like to experiment a little, open the Wires Window and change the number of segments on the wires, keeping
Test Drive the number the same for both. Then click Src Dat again to see the effect of this change on the source impedance. Repeat for several different numbers of segments. Close the Wires Window when you’re finished to get it out of the way.
Close the Source Data display.
Now we’ll make the dipole into an inverted vee. At this point, most other modeling programs would require you to do some trigonometry or carefully draw the inverted vee on graph paper to determine the coordinates of the wire ends. But not with EZNEC. We'll use EZNEC's Rotate feature to make it into an inverted vee with an included angle of 90 degrees.
Before proceeding, it’s a good idea to save the description. This way, an easy recovery can be made if an error is made.
Click the Control Center Save As action button. Furnish a name, such as “Temp” (don’t use “Last” – it’s used by EZNEC for the description present when the program ends), then click Save.
Open the Wires Window by clicking on the Wires line in the Control
Center information window.
With the mouse cursor over the X, Y, or Z coordinate cell of Wire 1,
End 2, click the right mouse button. (Remember, the mouse cursor has to be over the right cell, regardless of where the text insertion point is.)
This opens the shortcut list.
Select Elevation Rotate End. Enter the value -45, and click Ok.
This rotates end 2 of wire 1 downward 45 degrees, without changing end 1. In the View Antenna display, you should now see wire 1 drooping downward 45 degrees. Rotate the View Antenna display if desired by clicking in the display window and dragging with the mouse. If you don’t see this, you should return to the dipole by either re-entering the wire end coordinates or by reopening the file you saved a moment ago by clicking the Open action button and selecting the file. Then try the rotation feature again.
The 2D plot disappeared as soon as you modified the antenna wire. This is intended operation. EZNEC removes any displays that are no longer valid. As soon as you modified the wire, the display no longer represented the pattern of the current antenna, so it was closed.
Now repeat the rotation for the second wire.
With the mouse cursor over the X, Y, or Z coordinate cell of Wire 2,
End 2, click the right mouse button. Select Elevation Rotate End. Enter the value –45, and click Ok.
You should see the completed inverted vee in the View Antenna display.
If the inverted vee looks ok, close the Wires Window.
Click the FF Plot action button to generate a 2D plot.
The plot should resemble the dipole plot. To see how the pattern compares to the dipole’s,
Open the 2D Plot display File menu and select Add Trace. Locate the
Back Yard Dipole file you saved at the end of the “Along The
Straightaway” exercise and click Open.
Note that when automatic outer ring scaling is selected, it's scaled for the largest of all the plots being displayed. It can be shown that the center of current for a sinusoidal distribution is 1/3 of the way from the current loop.
This means that the effective radiation strength from the inner 1/3 of the inverted vee equals that from the outer 2/3 (since the current is heavier
EZNEC User Manual toward the center). If we raise the inverted vee by 3.94 feet, it will place this current center at 30 feet, which was the height of the dipole's center of current. Let's try it and see what happens:
Open the Wires Window. Open the Wire menu and select Change
Height by. Enter 3.94 in the bottom text box and click Ok or press
Again the 2D plot is closed as soon as the model is changed.
Close the Wires Window if desired, then click the FF Plot action button.
Add the Back Yard Dipole trace to the 2D display as you did before.
The higher inverted vee is closer to the dipole pattern but still has slightly lower maximum gain. This shouldn't be surprising if you investigate the patterns in more detail. The inverted vee has more radiation off the end, reducing the gain from the side. But as you can see, the gain difference between the dipole and inverted vee is less than one dB (providing the centers of current are at the same height).
This concludes the “Through The Curves” exercise. If you’d like to learn some
. You can continue directly from here, or you can exit EZNEC and do it later.
On The Race Course
This section takes you through some of EZNEC’s more advanced features.
Open the back yard dipole model included with EZNEC:
Click the Control Center Open action button, and select and open the example file BYDipole.ez.
Let's look at the full 3D pattern.
Click the Plot Type line in the Control Center information window.
Select 3 Dimensional, then Ok.
You’ll see a notice that EZNEC is reducing the plot resolution to 5 degrees per step. The minimum step size for 3D plots is 2 degrees, although this is too dense for general use. One degree resolution is a good choice for 2D plotting, and the example file was set to this value.
Click Ok to close the message box.
Click the FF Plot action button to start the calculation.
When the calculation finishes, you'll see a full three-dimensional (3D) display of the dipole pattern. You'll note that it doesn't look much like the textbook pictures you may have seen. This is because the textbook pictures usually show a dipole in free space or, at most, over a perfect ground. This, on the other hand, is the model of a dipole over real ground.
You can move the 3D display around to view it from different angles. Position the mouse cursor anywhere on the 3D plot window. Press and hold the left mouse button down as you move the mouse. The mouse cursor has to be in the 3D plot window when the button is initially pressed. However, once the button is down the mouse cursor can be moved anywhere on screen. You can also do fine positioning with the arrow keys, as long as you first click anywhere in the 3D plot window.
One of EZNEC’s powerful features is the ability to view individual 2D “slices” of the 3D display. To use this feature, the 3D display control box must be activated. If you see some controls to the left of the plot, the control box is on.
If not, you need to turn it on at this point by opening the 3D display View menu and selecting Show Controls.
In the control box Highlight section, choose Elevation Slice.
The 3D plot will dim, and an elevation “slice” will appear in a distinctive color.
(You can modify these colors via the 3D display Options menu Colors selection.) The two control box scroll bars are now active, and can be used to change the slice and to move the cursor.
Most of the scroll bars in EZNEC can be adjusted in several different ways.
You can click on the arrow boxes at the ends to move the control a single step. Holding the left mouse button down when on an end box moves the control rapidly. If you click in the area between the adjustment bar and the end box, the control will move in larger steps. Or you can simply drag the adjustment bar to the desired position. Finally, the keyboard arrow keys will move the control if it has focus (that is, if it’s the currently active control).
Now click the Show 2D Plot box at the bottom of the 3D display control box.
This turns on the 2D display, where the currently highlighted “slice” of the 3D plot is shown. Notice that as you change the 3D “slice” and the cursor position, the 2D plot changes accordingly. Turn on the 2D display control and data boxes as follows.
On the 2D plot, open the View menu. If Show Controls isn’t checked, select it. Repeat for Show Data if it isn’t checked.
The 2D display controls track the corresponding controls on the 3D display.
So once a 3D plot has been calculated, various “slices” can be selected directly from the 2D display if desired.
When the Plot Type is 3D, the only way to open the 2D display is from the 3D display (either by checking the Show 2D Plot box in the control box, or by selecting Show 2D Plot in the 3D display View menu). If you close the 3D display and want to reopen it, click the FF Plot action button in the Control
Experiment with the 2D and 3D controls, selecting different “slices” and
“slice” types, and moving the cursor.
You can move the cursor in the 2D display by clicking in the 2D plot window.
After clicking in the 2D plot window, the cursor can also be moved with the arrow keys and <Page Up> and <Page Down> keys. And, when the 2D control box is being shown, you can move the cursor with the appropriate scroll bar.
Various information about the 2D pattern is shown in the 2D display data box
(under the plot). One entry, on the right side, is the gain given as “dBmax”.
This is the gain relative to the maximum value anywhere in the 3D pattern.
Open the View Antenna display by clicking the Control Center View Ant action button. In the View Antenna display, open the View menu and select Objects. Check the 2D Pattern box and click Ok.
The 2D “slice” now appears on the View Antenna display. This shows how the
“slice” is oriented relative to the antenna. Notice that as you change the selected “slice” with either the 2D or 3D controls, the View Antenna display changes accordingly. Also notice that as you rotate either the 3D or View
Antenna display, the other changes position to match. (They don’t track moment to moment, but synchronize when the mouse or keyboard key is released.)
One last point to mention before leaving the 3D display. You can save a 3D plot from this display (File/Save 3D Plot), but you can't open one from the 3D
EZNEC User Manual display or superimpose 3D plots. You can specify any azimuth or elevation
“slice” of a saved 3D plot to add to the 2D display. Or, you can recall and view
Close all the windows except the Control Center.
Now let’s run an SWR plot of the antenna.
Click the SWR action button. Enter 14, 14.4, and .1 in the Start
Frequency, Stop Frequency, and Frequency Step boxes respectively.
Then click Run.
This will run an SWR sweep, with the results being shown when the sweep is finished.
Turn on the control and data boxes via the SWR display View menu, if they’re not already on.
You can move the cursor on the SWR graph to any position by clicking on the graph near the point where you want the cursor to go, or by dragging the cursor. You can also move the cursor with the arrow keys after first clicking anywhere on the SWR graph. As the cursor moves, you can see the SWR for that frequency in the data box below the graph.
The graph clearly shows that the antenna is too short, if lowest SWR on 20 meters is a goal. This is indicated by the fact that the SWR decreases clear across the band.
Let’s make the antenna resonant at 14.1 MHz. One way would be to adjust the lengths of the wires and find resonance by trial and error. But we’ll use another method. First we find out just where the antenna is currently resonant.
We know it’s at or above 14.4 MHz, so
Click the SWR action button. Click No in the message box which appears. Enter 14.3 and 14.8 in the Start and Stop frequency boxes, and click Run.
From the graph, the SWR looks lowest at around 14.42 MHz or so. What we’ll do is change the frequency to 14.42, about where it’s resonant. Then we have a resonant antenna but at the wrong frequency. We’ll then rescale that resonant antenna to the right frequency.
In the Control Center information window, click the Frequency line.
Enter the value 14.42, then Ok. Click the Frequency line again. Enter the value 14.1. But this time, check the Rescale box before clicking Ok.
Open the View Antenna display by clicking the View Ant action button. Rightclick on the wire in the View Antenna display. You can see that EZNEC has lengthened the wire to about 34.2 feet. (It was originally 33.43 feet.)
Close the View Antenna display. Click the Control Center Src Data action button.
The source impedance still has a slight negative reactance (about –4 ohms), indicating that the antenna is still a little short. The SWR/rescaling process could be repeated, or the antenna length changed in the Wires Window to fine tune it. Let’s run another SWR sweep to see how close we got to the target of
Close the Source Data display. Click the SWR action button. Enter 13.9 and 14.4 for the Start and Stop Frequencies, then click Run.
From the result, you can see that we got pretty close to 14.1.
There are a couple of reasons we didn’t hit it exactly. One is that we guessed at the initial resonant frequency. Another SWR sweep with a finer step would have been more precise. The second reason is that when an antenna is
Test Drive scaled, the wire diameter isn’t changed if it’s specified as an AWG gauge. The diameter of our antenna wire is specified as #12, so it wasn’t changed with the scaling. Exact scaling requires changing the wire diameter in the same proportion as the antenna length. EZNEC doesn’t do this when wire diameter is specified as a gauge, because it would usually result in a diameter which doesn’t correspond to any standard wire size. Ground conductivity also doesn’t scale linearly with frequency. This will generally make a noticeable difference only with the patterns of vertically polarized antennas, however.
You might want to feed the antenna with 75 ohm line instead of 50 ohm line.
An alternate Z0 is available for analysis. It's set in the Control Center information window, as Alt SWR Z0. Since we didn't change it, its value is 75 ohms, which was the value in the DIPOLE1 description we started with. To see what the SWR would be on a 75 ohm feedline,
Select the Alt option in the SWR display control box Z0 section.
75 ohm feedline feeding this antenna would have a lower SWR than 50 ohm line. (However, the SWR is low enough that it's unlikely to make any difference in performance unless the feedline is exceptionally long or lossy.) If analyzing an antenna with more than one source (such as the example antenna 4Square), you can select which source to view using the up-down control in the SWR display control box.
This concludes On The Race Course, and the Test Drive.
Now you've taken EZNEC for a good run. The
gives tips for creating models and interpreting results. The Reference chapter contains complete information about each menu and its features.
section contains an additional step-by-step tutorial that illustrates additional EZNEC features. You might want to go through it now or at a later time.
Upgrading from DOS EZNEC or EZNEC pro
All plot (trace) and description (.EZ or .EN) files created by ELNEC or earlier versions of EZNEC are directly usable by EZNEC v. 4.0.
Description files written by EZNEC v. 4.0 can be used with earlier EZNEC versions. ELNEC can read EZNEC v. 4.0 description files, but source and load placement might require modification. Plot (trace) and ground data files written by EZNEC v. 4.0 are usable by EZNEC and EZNEC pro v. 2.0 or later versions, but not by earlier versions.
Although description files are compatible among all versions, files created with
EZNEC v. 4.0 contain additional information. If a description file is opened with an older version of EZNEC, then saved with the original name by the older version, some of the additional information will be changed or lost. For example, if a description file created by EZNEC v. 4.0 is opened with EZNEC
v. 3.0 or earlier, saved with the older program under the same name, then reopened with EZNEC v. 4.0, the frequency sweep setup information will be gone. Antenna notes files, which are separate from the description files, won’t be affected; they’re simply ignored by older versions.
There should be no conflicts between EZNEC v. 4.0 and DOS versions installed on the same machine. The same directories for description files, ground files, etc., and even program files, can be used. Even when installed in the same directory, EZNEC v. 4.0 won’t overwrite DOS versions.
(Maintenance updates and other revisions of EZNEC v. 4.0 will, however, generally overwrite earlier revisions of v. 4.0.)
What's New Since DOS
The Big Difference
From an operational standpoint, the main difference between EZNEC v. 4.0 and its DOS predecessors is the ability to view multiple windows simultaneously. On the surface this may seem like a trivial difference, but it enhances EZNEC’s usability tremendously. Just a few minutes of working with EZNEC v. 4.0 will easily convince you. For example, with the Wires and
View Antenna Windows open at the same time, you immediately see changes as you make them. You can select wires in either window, and they’ll be selected in the other. The wire or wires selected in the Wires Window are highlighted in the View Antenna display. Or, view the 3D pattern plot and View
Antenna display at the same time. Both rotate together, so the orientation of the antenna with respect to the pattern is easily apparent. With the 2D and 3D pattern plots open at the same time, the position of the 2D “slice” in the 3D display is always apparent.
Of course you also have all the advantages of the Windows interface, with mouse operation, menus, printer compatibility, and all the other advantages it offers.
Best advantage can be taken of EZNEC v. 4.0’s capabilities with a 17 inch (43 cm diagonal) or larger monitor with 1024 X 768 pixel or higher resolution.
Upgrading from DOS EZNEC or EZNEC pro
However, you’ll still benefit greatly even with a notebook computer and VGA display.
The Windows environment has made it practical to include detailed notes for each antenna. Antenna notes are created and edited via a selection in the
Control Center File menu. Antenna notes are saved in plain ASCII text files which have the same base name as the antenna description, but the file extension “.txt”. They’re kept in the same directory as the antenna description
in the Reference chapter for more information.
Antenna notes files can be edited with any text editor, and otherwise treated like any other text file.
(EZNEC pro only): Antenna notes are handled differently for NEC-format description files. In NEC files, antenna notes are integrated into the description file as CM “cards”. When you choose to edit the antenna notes with EZNEC, the CM “cards” are converted to plain text and put into a temporary file, which is then opened with EZNEC’s editor. When this file is
“saved”, the text is put back into the NEC file as CM “cards”. The CM “cards” can be edited with another text editor if desired.
RLC Load Type
A new RLC load type has been added to the existing R + j X and Laplace types. This in turn includes three RLC configurations, with the ability to make the R frequency variable to simulate conductor or dielectric loss.
Other New Features
EZNEC now supports winSMITH by Noble Publishing, as well as ARRL’s
is a powerful new feature to detect source placement problems and to determine ground and wire loss
Faster calculation – EZNEC’s NEC-2 engine is 20% faster than previous versions. (The EZNEC/4 NEC-4 engines are about the same speed as previous versions.)
now shows wire numbers. You can center them, offset them, or turn them off.
The View Antenna Display now indicates end 1 of highlighted wires with a distinctive color.
Context sensitive help – When running EZNEC v. 4.0, press F1 to display information about the currently active window, menu, or control.
Names and operations have been changed to reflect current Windows usage.
The following list isn’t complete, but gives examples of changes:
EZNEC v. 4.0
Main Menu Control Center
Wires, Wires, Sources, etc.
EZNEC User Manual
Sources, etc. Menus Windows)
Exit Exit without saving
Recall (file) Open
Browse (file) View
Selected Operational Differences
As much as possible, the best features of using DOS EZNEC have been retained, while at the same time creating a true Windows interface. It is hoped that the location and use of most features will be intuitive and selfexplanatory. However, a few changes bear pointing out to ease the transition from earlier EZNEC versions.
2D, 3D, and View Antenna display positioning
To rotate the 3D or View Antenna display, press the left mouse button while the mouse cursor is in the display window. Holding the button down, move the mouse to rotate the display. To move the cursor in the 2D display, click the left mouse button anywhere in the display window and the plot cursor will move to the nearest possible point which is on a line from the plot center to the mouse cursor location. The cursor can be dragged with the mouse if desired. Other positioning is done via the Controls box to the left of the display window. This box is turned on and off from the 2D, 3D, or View Antenna display View menu.
Data and Control Boxes
The 2D plot and SWR displays include a Data display which can be turned on or off via the form’s Options menu. These contain the former 2D Analyze data, and the data which appeared to the left of the SWR plot. The 2D, 3D, SWR, and View Antenna Displays all have a Controls box which also can be turned on or off via the form’s Options menu. All the Data and Controls displays should be turned on when you first run the program. From then on, their states will be remembered and restored the next time you open the particular display.
Shortcuts and Right-Clicking
All of the shortcuts such as rotating wires and wire end connections (formerly in the Wires Menu) have been retained. In most cases, you can enter the same combinations of letters and numbers as before. For example, you can enter ‘RA45’ in any X, Y, or Z column in the Wires Window to rotate the wire
45 degrees in azimuth, or enter ‘W1E2’ to connect the end to End 2 of Wire 1.
But you can also access these features, and others, by right-clicking on the cell. Generally this is the method of accessing alternate methods of entering data. For instance, right-clicking a cell in the Transmission Lines Window Z0 column opens a dialog box allowing you to specify a type of transmission line or to specify the line in terms of wire spacing and diameter.
Upgrading from DOS EZNEC or EZNEC pro
Drop-down lists are sometimes incorporated in the Input Grid Windows. For example, in the Sources Window, clicking on the Type column will make a drop-down list arrow visible. Clicking the arrow activates a drop-down list containing the available choices.
Uninstalling DOS EZNEC
EZNEC v. 4.0. However, you may want to uninstall it to recover some disk space. All of the files listed below can be deleted without affecting your saved antenna descriptions, traces, or ground data files. Some may not be present, depending on the version you have. All are located in the EZNEC program directory. Deleting these files will uninstall DOS EZNEC (EZNEC v. 1.0 or
Files which can be deleted
KEYFILE.### (### is a three-digit number)
LAST.### (### is a three-digit number)
Building The Model
Introduction to Modeling
Modeling is the technique of evaluating the performance of one object or system by evaluating the performance of a substitute called a model. Models can be physical objects, like a reduced size scale model antenna sometimes used for evaluating HF antennas. Models can also be purely mathematical, like the equations you use in circuit analysis. The accuracy of the results are never better than the accuracy with which the model matches the real object.
For example, a model of a circuit consisting of a battery and resistor will do a poor job of predicting the current if the battery is old and the model doesn’t include internal resistance. Likewise, a model for analyzing UHF circuits which doesn’t include accurate inductive and capacitive effects won’t produce accurate results. So it’s imperative that you learn the limitations of your modeling tools. This manual will help you in that endeavor.
Skillfully used within its limitations, EZNEC can do a remarkably accurate job of predicting antenna performance. But remember, it’s analyzing a model of an antenna, not an actual antenna. So its accuracy is always limited by the accuracy of the representation of the real antenna and its environment by the model. In some cases, the tools simply are not available to make an accurate representation, so approximate results are the best that can be obtained. For example, a parabolic reflector can be approximately modeled as a wire grid, but the representation will not accurately predict low-level lobes or characteristics sensitive to dish smoothness. But for many antennas under a wide range of circumstances, EZNEC will give you startlingly accurate results.
And for most antennas, the results will be close enough for nearly any practical use.
Building a good model and interpreting the results requires considerable skill.
This manual is intended to help you acquire the skills necessary to get consistently good results.
You may want to take the
before or during the reading of this chapter.
Modeling With EZNEC
All antenna models are made from EZNEC components – wires, sources, loads, transmission lines, and ground media. The accuracy of the model depends on how accurately the actual antenna and its environment can be represented by the model made from these components. Some physical objects, like a physical wire or metallic tube, are easily modeled with high accuracy. Some, like a round loop or small flat metal plate, must be approximated. And some, like a helically wound dipole antenna, can’t be modeled accurately at all with the available components. But a very wide variety of objects can be successfully modeled with EZNEC.
All EZNEC operations are accessed via the
. This is the form which opens when you start EZNEC, and stays open while EZNEC is running.
The following sections will lead you through the steps of building a model. You can get additional information by clicking on the links.
Building The Model
Opening The Description File
EZNEC doesn’t have a provision for starting with a blank description; it always begins with the last antenna you’ve analyzed. So it’s helpful to accumulate a collection of template antennas which are similar to the types you commonly model. These make fast and easy starting points for developing your new model.
A description file is opened by clicking the Control Center Open action button, or clicking the Open selection in the Control Center File menu.
EZNEC pro only: To open an NEC-format file, follow the above procedure, but include the extension .NEC when you enter the file name. Likewise, to save a file in NEC format, include the .NEC extension.
Modeling The Antenna Structure: Wires
When modeling an antenna, you’ll generally spend most of your time working on the physical structure made up of the antenna’s conductors. That’s the subject of this chapter.
It’s important to realize that EZNEC doesn’t know, or care, what you consider to be the “antenna” and what other conductors in the model might represent. If you’ve included conductors to represent towers, rain gutters, fences, or other antennas, they’re just as much a part of the model and the calculation as the part of the model you consider to be the “antenna”. The whole model is a single coupled system to EZNEC just as it is in the real world. (I’ve often commented to amateurs seeing strange results from multiple antennas in a small area that they don’t have several antennas – they have one antenna with several feedpoints. And this is just how EZNEC looks at it.)
All antennas in an EZNEC model are made from “wires”. In this manual the term “wires” refers to the EZNEC component of that name. Real, physical wires are called “physical wires”. The distinction is important because EZNEC wires are idealized models of the real thing, much like a resistance is an idealized model of a resistor. EZNEC wires are also used to model other physical objects such as tubing. Connected as a grid, or screen, they can also be used to model flat conductive surfaces.
EZNEC models every antenna as a collection of straight wires. Straight should be emphasized; a round loop, for example, must be modeled as a polygon of straight wires. The diameter of each wire can be freely chosen, and the program will give accurate results with diameters from arbitrarily small up to at least 0.02 wavelength. With some imagination, nearly any type of conducting structure can be modeled as wires (although not always practically or with great accuracy). For example, a metal wall can be modeled as a grid of wires with a mesh on the order of 0.1 wavelength or less.
You tell EZNEC where the wires are placed in space by giving their x, y, and z coordinates relative to a universal origin, or 0,0,0 point. You're free to decide where the origin is, except that ground is always assumed to be at the height of the origin (z = 0). (There are also some additional considerations involving
are included in the model.
EZNEC has several features to make entry within the coordinate system as easy as possible; they're described in the
EZNEC User Manual
Wires are connected whenever an end of both have the same coordinates
(actually, if the ends are within about 0.001 segment length of each other).
Wires can be connected only at their ends. EZNEC automatically connects wire ends which have very nearly identical coordinates. The actual criterion used by EZNEC is that wire ends have to be within about 1/1000 of a
on (the default), the coordinates of any wire ends which are close enough to be considered connected will be modified as necessary by EZNEC to make them identical. If a ground is used, a wire is connected to ground if its z coordinate is within about 1/1000 segment length of zero. When Auto
Coordinate Match is on, the z coordinates of ground-connected wires are modified by EZNEC to be exactly zero. (NOTE: For High Accuracy ground, the connection will be quite lossy (resistive). See
Serious errors will occur if wires cross or occupy the same space. Because wires can be connected only at their ends, simply crossing wires won't connect them, and will cause severe calculation errors. (The calculating engine won't object to wires crossing at segment junctions, and will consider them connected. However, these connections won't be recognized by the interface portion of EZNEC, so errors can easily be made. Also, any change in wire length, orientation, or number of segments will break the connections.
Therefore, attempting to make connections at segment junctions other than wire ends is strongly discouraged.) As an example, modeling an "X" - shaped structure with the recommended restrictions requires four wires if the cross members are connected at the center of the "X”.
Modeling the following wire grid requires 24 wires. Each side of each square is a separate wire.
A common problem involves wire spacing. When wires are to be close but not connected, users frequently space them very close, sometimes a fraction of an inch or centimeter when the wavelength is tens of meters. This isn't good practice, and can lead to numerical problems. (It's difficult for any program to deal with wires which are 40 meters long but spaced .0001 meter apart.)
Always use realistic spacing. If you're analyzing a 3 MHz antenna, you probably can space wires six inches (15 cm) without materially affecting the antenna operation. If you can, do so. If you can't, make sure the results aren't
Building The Model unduly sensitive to the spacing or number of segments. If they are, numerical problems might be occurring. More information about closely spaced wires and wires intersecting at an acute angle is given in the sections below.
Wires are divided into segments for computational purposes, and good segmentation is essential to accurate results. See the
for more information about this important topic.
Several NEC guidelines are checked by the automatic
runs automatically when you open a file or change the wire description, or you can run it manually at any time. There are two sets of guidelines: conservative and minimum recommended. In general, the conservative guidelines will result in more segments and better accuracy than the minimum recommended. It's impossible to place an accuracy figure on either set of guidelines, because the effect of small errors in current amplitude or distribution can vary greatly, depending on the type of antenna and the role the wire plays. As a general rule, you should use more conservative guidelines when modeling antennas which have a narrow bandwidth or use parasitic elements, such as a Yagi. See
Bear in mind that the Segmentation Check doesn't report all possible errors, so care and knowledge on the part of the user is still required.
section describes special considerations which need to be taken when modeling several common configurations. Additional
display can be found in the Reference section.
Each wire is divided into segments for analysis purposes. The NEC calculating engine assumes that the current has an essentially sinusoidal shape over the length of a segment, and that the currents of adjacent segments match at their junctions. This makes the problem one of finding a finite number of impedances, currents, and field strength contributions. Some of the skill in modeling is in choosing the number of segments. EZNEC will choose for you (with its
feature) if you wish, but its choice will often not be best. Although accuracy generally improves when more segments are specified, computation time increases approximately as the square of the number of segments. A useful rule of thumb is 10 segments per half wavelength for pattern/gain analysis, and perhaps twice that number if really accurate impedance values are required. Wires joining at very acute angles may require more segments (see
straightforward way of telling whether you've specified enough is to increase the number and see how much the results change. You should also develop the habit of looking at the currents on the wires. Abrupt current changes might indicate an insufficient number of segments (but note that apparently abrupt phase reversals at wire end connections may be due to internal conventions of assigning current direction – see
). One place more segments aren't better is if wires of different diameters are connected in a configuration which EZNEC can't correct with its stepped diameter correction.
(This isn’t a problem with the NEC-4 engine in EZNEC/4.) See
sounds. You'll soon get a good feel for about how many you need to get the shape of a pattern or a feedpoint impedance with the accuracy you need.
EZNEC User Manual
In looking at models created by EZNEC users, it’s apparent that many people use more segments than necessary. This is no disadvantage in small models, but it unnecessarily increases calculation time, and often is the source of a perception that not enough segments are available. One important thing to keep in mind is that if a wire carries little current, it contributes little to the overall field, since the field is proportional to the current. Consequently, wires that carry little current can often be given fewer segments than the “minimum recommended” number, or even removed from the model altogether. The exception to this is situations where deep nulls or high front-back ratios have to be determined. In those cases, even the small fields from wires with little current can modify the results and should be undersegmented or removed with care. When studying the effect of an undriven nearby antenna, the model of the nearby antenna can frequently be undersegmented or simplified a great deal. For example, the elements of a 20 meter beam are far from being resonant on 15 meters, so constant diameter, somewhat undersegmented elements could be used for the 20 meter beam when analyzing its effect at 21
section for segmenting that type of antenna might give you some ideas for others.
examples where the number of segments or segment length requires special consideration. Also see the index under “Segments” or “Segmentation” for additional references.
EZNEC permits a total of 500 segments. EZNEC pro programs EZNEC-M and EZNEC/4 permit 10,000.
Using The Wires Window
Other than the Control Center, the Wires Window is probably the part of the program you’ll interact with most. This is the place where the basic structure of the antenna is defined. The antenna is made from straight wires. The location, diameter, and interconnection of these wires are all defined in the
The Wires Window is opened by clicking on the Wires line in the Control
Center Information Window.
Open the Wires Window by clicking on the
Wires line or the button to its left.
Wires are defined by specifying their end coordinates in the appropriate grid cells. Menus and selections in the following paragraphs refer to the Wires
Window. Unless otherwise noted, a sequence like Wire/Add refers to first the menu, then the selection(s). For example, Wire/Add means the Add selection in the Wires menu (in the Wires Window).
To add any number of wires, select Wire/Add. Enter the number of wires in the upper box. If the lower box is left unchanged, the new wire(s) will be added below the existing wires. If desired, you can specify other locations for the new wire(s) by entering the position in the lower box.
To add a single wire, you can also simply type the coordinates, diameter, and number of segments in the add row, then press <Enter> or click on another row of the grid. Any cells left blank will be filled with duplicates of the values for the last wire.
Entering End Coordinates
Building The Model
Coordinates are entered in the appropriate columns of the grid. Coordinates can also be modified by means of editing
Numbers must use the decimal separator defined by your Windows regional setting.
Entering Wire Diameter
Diameter can be entered as a number or as American wire gauge (AWG).
The units used for numerical diameter are shown near the top of the grid column. To enter diameter as a wire gauge, prefix it with ‘#’. For example,
AWG 12 wire is specified as #12. Note that wires specified as gauge aren’t
Entering The Number of Segments
The number of segments is entered in the Segs column. Choosing the correct
for more information.
Defining Wire Insulation
for a full description of this feature.
Deleting, copying, and moving wires require first selecting which ones are to be operated on. In addition, wires can be selected before starting
. To select a wire, click on the button on the left side of the appropriate row. The selected wire will be highlighted. To select additional wires, hold
<Ctrl> down when clicking the button. To select a group of wires, select the first wire, then hold <Shift> while clicking the last wire in the group.
The current wire, or selected wires, can be deleted by pressing the <Delete> key. Alternatively, a sequential group of wires can be deleted by selecting
Wire/Delete and specifying which to delete.
Changing the Position of Wires in the List
To move wires in the list, first select the wires as described above. Then Move
Wire(s) in List from the Wire menu. You’ll be asked for the location in the list for them to be put. You can also select Wire/Copy or Wire/Move Wire(s) in
List before selecting wires, in which case you’ll be asked for a range of wire numbers to copy or move.
Copying, Moving, and Rotating Wires
To copy, move, or rotate wires in the model, first select the wires as described above. Then open the Wire menu and select Copy Wires, Move Wires XYZ,
Rotate Wires, or Stack. The individual dialog boxes offer additional choices for the action you’ve chosen. You can also choose the action from the Wire menu before selecting wires, in which case you’ll be asked for a range of wire numbers to copy or move.
Wires can be modified individually, or if desired, a group of wires can be modified at the same time using the
feature. The procedure is the same for both cases, except that to modify a group of wires, Group Modify must first be activated.
Basic modification of one parameter is done simply by entering the new value in the cell, then pressing <Enter> or clicking on a cell in another grid row. But
EZNEC also has a number of shortcut features that make it easy to modify
Modifying A Group of Wires – Group Modify
EZNEC User Manual
for information about this powerful feature.
Changing the Antenna Height
To change the height of the entire antenna or any group of wires, select
Other/Change Height By, and enter the amount by which you want to change the height. This simply modifies the z coordinate of both ends of all wires by the specified amount.
Printing or Saving the Wire Coordinates
To print the wire coordinates or save them to a file, select Other/Print/Save
Wire List. This opens the EZNEC Editor with a formatted list of the wire coordinates. You can save or print the data from this window. For a similar display which includes other features of the model such as sources and loads,
EZNEC has a number of very powerful features for modifying groups of wires, located in the Wires Window Wires menu. There are also several powerful features in the Create menu, described in the
Wire Information (wire, segment length) – You can see the wire and segment length for any wire by right-clicking the box at the left of the row.
Importing Wires – Wire end coordinates can be imported from a simple ASCII file. This isn’t intended to substitute for EZNEC’s file format, but primarily as a way to import wire end coordinates generated by another program. Wires are imported by selecting Import Wires
From ASCII File in the Other menu. The file format is detailed in the
existing description or you can replace the existing wires with the imported ones. See
Change Units, Retain Numbers – This option allows you to recover from an easy trap to fall into. It’s easy to begin entering data only to find that you’re not using the units you intended. For example, you might be entering data intended to be in meters into a grid where the units are feet. This option, in the Other menu, lets you recover without having to re-enter the coordinates. It will change the units but leave the numbers you entered (and all others in the grid) intact.
Coord Entry Mode – This check box is just above the data entry grid.
When checked, all columns except the wire coordinate columns are skipped. This allows faster entry of a large number of wire coordinates.
Preserve Connections – This is a powerful feature but it must be used with caution. Be sure to save your description before making wire modifications with this feature, and keep the View Antenna display on.
When Preserve Connections is on and you modify a wire end, all connecting wires are also modified so their connections to it are
connections of all modified wires. If selected wires are both modified and connected to each other, unpredictable results can occur. So be sure to save your description after verifying that each operation did
Building The Model what you intended and before doing the next modification. Preserve
Connections is turned off each time you close the Wires Window.
chapter of the
Tip: Turn on the View Antenna display when entering or modifying values in the Wires Window. This allows you to immediately see the changes you’ve made.
Wire Coordinate Shortcuts
EZNEC includes powerful features to help you modify wires without having to determine coordinates. For example, you can easily change the length of a wire, or rotate it about one end. Shortcuts can be applied to either individual wires or, in Group Edit mode, to groups of wires.
Wire coordinate shortcuts can be applied in two ways, both in the Wires
Window. One is to right-click any coordinate cell in the Wires Window grid.
The other is to enter a special shortcut abbreviation for the desired action into a coordinate cell. (Shortcut text abbreviations aren’t case-sensitive.) Each of the selections below appears in the popup menu you get if you right-click one of the coordinate cells. For example, to use the first method to change the coordinates of wire 4 end 1 so that it connects to wire 3 end 2, you right-click the X, Y, or Z column in the End 1 group of the Wire 4 row. This opens the shortcut popup menu. Select Connect End To. In the dialog box, enter 3 in the
Wire to connect to box, and 2 in the End to connect to box, then click Ok or press <Enter>. To use the second method, enter W3E2 in the X, Y, or Z column in the End 1 group of the Wire 4 row, then press <Enter> or move the mouse cursor to another cell.
Unless otherwise noted, the shortcut is applied only to the end of the wire where the mouse cursor is located when the right mouse button is pressed.
This will be called the “current end”. A change will be applied only to the current wire (that is, the wire number of the row where the mouse cursor is located when the mouse is right-clicked) unless in Group Edit mode. If in
Group Edit mode, the change will be applied to all selected wires. See
All shortcuts except Change Coordinate By will or can change all three of the end coordinates (x, y, and z) regardless of which of the three cells the mouse cursor is placed on or where the shortcut text abbreviation is entered.
International users please note: Floating point numbers (numbers with a fractional part) must have the proper decimal separator.
NOTE: Only the Connect End To shortcut is available in the Add Row (the blank line at the bottom of the grid).
Connect End To
This is a convenient way to connect a wire end to an end of another wire.
Simply specify the wire number and end to which you want the current end connected. The text abbreviation for this shortcut is W#E# where # are the number of the wire and end you want to connect to. See the example above.
Change Coordinate By
This shortcut adds or subtracts the specified amount to or from the current end coordinate. Unlike all other shortcuts, this affects only the particular coordinate where the entry is made. The text abbreviation for this shortcut is
++# to increase, or - -# to decrease, the coordinate by #. For example, to
EZNEC User Manual decrease the Wire 4, End 2 y coordinate by 3, you can enter - -3 in the appropriate cell.
Change Length By
This shortcut changes the length of a wire by the specified amount. The current end is modified while the other end is fixed. Wire direction is unchanged. The text abbreviation for this shortcut is L+# to increase the length by #, or L-# to decrease it by #. The length of a zero-length wire can’t be changed because the direction isn’t defined.
Change Length To
Use this shortcut to make the wire a particular length without changing the wire direction. The current end is modified and the other end is fixed. The text abbreviation for this shortcut is L# to change the length to #. The length of a zero-length wire can’t be changed because the wire direction isn’t defined.
Multiply Length By, Divide Length By
These function like Change Length By, above, except they multiply or divide the length by the specified amount rather than adding or subtracting a fixed amount. The text abbreviation for this shortcut is L*# to multiply and L/# to divide.
Elevation Rotate End, Azimuth Rotate End
This shortcut rotates the current end of the wire, leaving the length and other end fixed. The rotation amount is specified in degrees. For elevation rotation, a positive angle causes rotation upward, negative downward. For azimuth rotation, a positive angle results in counterclockwise rotation, negative in clockwise rotation. When elevation rotation is done, the azimuth angle of the wire is unchanged. A vertical or near-vertical wire can’t be rotated in elevation because the azimuth angle is undefined. When azimuth rotation is done, the elevation angle of the wire is unchanged. The text abbreviation for these shortcuts are RE# and RA# for elevation and azimuth rotation respectively, where # is the angle to rotate in degrees.
Additional operations and more detailed information can be found in
Realistic wire loss can be included in the model. In the vast majority of typical antennas, wire loss doesn’t cause enough difference to be of concern, but it can be important particularly with electrically small antennas. Currently, only one type of metal or one amount of resistivity and permeability can be specified for the entire antenna model. However, only one part of the model or another typically dominates the loss, and choosing its characteristic will produce good results. If the metal is plated, the plating material should be specified unless the plating is exceptionally thin or the frequency low. EZNEC assumes that the specified material is at least several skin depths thick at the analysis frequency. Copper-clad steel wire consisting of a thick layer of copper over steel will have the loss characteristics of copper, so that metal should be specified. If you’re not sure whether a plating is several skin depths thick, run a calculation with the resistivity of the plating metal, then with the underlying metal. The actual antenna performance will be somewhere between these limits. (In some special circumstances, it can theoretically be a bit outside the limits, but not enough to be likely to alter any conclusions about antenna performance.)
Building The Model
Wire loss is specified by clicking the Wire Loss line in the Control Center
Information Window. This opens a dialog box which allows you to choose from a number of common metals or enter the resistivity and permeability.
Please note: The value used by EZNEC is the bulk resistivity of the metal, not the DC or RF resistance per unit length of the wire. The bulk resistivity doesn’t change with wire diameter; it’s a function only of the metal of the wire or the outer layer of the wire if plated (assuming, as EZNEC does, that the outer layer is at least several skin depths thick). EZNEC calculates the skin depth from the bulk resistivity and frequency, and uses that and the diameter of the wire to determine how much resistance each wire has. If you know the resistance per unit length of a solid, non-plated or –layered wire, you can calculate the bulk resistivity of the metal from R b
= R’ A where R b
is the bulk resistivity in ohm-meters, R’ is the wire’s resistivity in ohms per meter length, and A is the cross-sectional diameter of the wire in square meters.
Wire loss is especially important to include in a model showing low source resistance. In these antennas, wire loss can sometimes be substantial. You can determine the amount of loss caused by the wire by calculating the pattern with zero wire loss and realistic wire loss and comparing the gain.
If feedpoint resistance is very low and your model has a single source, you should temporarily remove the wire loss to insure that the source resistance isn’t negative. A negative source resistance with a single source model is an indication of numerical problems, and it can sometimes be concealed by wire
for more information.
Important note: The Wire Insulation feature is accurate only for a thin insulation layer, and dielectric constants in the range of those of typical wire insulating materials. Attempts to extend its use to purposes other than simulating the effect of wire insulation will produce inaccurate
EZNEC v. 4.0 has the capability of including the effect of wire insulation. Only the pro programs provide for lossy insulation, but the loss of normal insulation coatings will have virtually no effect on antenna performance. The loss feature is useful only for very unusual circumstances, not typically encountered. The parameter choices appear as new columns in the Wires Window grid. These columns can be hidden for convenience if desired, via the checkbox above the grid. If you right-click any of the insulation columns, you'll get a dialog box for convenient entry. Here's how the dialog box works:
The first three fixed choices, PVC (polyvinyl chloride), PTFE (Teflon), and PE
(polyethylene or polythene), will enter values for dielectric constant (k, or relative permittivity) and (pro only) loss tangent into the grid but won't alter the thickness value already in the grid. The None choice and the three custom choices will replace the thickness value. Choices, including custom values, are saved permanently unless you close the dialog box with <Esc> or Cancel.
The intent of the custom values is to let you enter parameters appropriate for some specific wire you might be using for antenna construction.
To set insulation to zero, enter a thickness of zero. For convenience, there's a
None choice in the dialog box which will do this. A dielectric constant of 1 and
(pro only) loss of zero will result in no effect. However, calculations will be done any time the thickness isn't zero.
EZNEC User Manual
Insulation thickness is scaled when the antenna is scaled. Insulation properties of added wires are copied from the wire just preceding, as are the diameter and number of segments.
The Segmentation and Geometry checks and the stepped diameter correction don't take any notice of the insulation, since its effect as a percentage of wire length is generally small (typically on the order of 2 - percent. Segment length rules won't change significantly when using wire insulation unless (EZNEC/4 only) the insulation is on buried wires and is relatively thick. When the insulation's dielectric constant is considerably lower than that of the medium
(possible only with buried conductors, available only with EZNEC/4), the velocity factor increases significantly, so segments can be longer. This is under consideration for a future modification of the Geometry Check feature.
The characteristics of PVC vary widely, so the values are a rough average for the HF range. The Custom windows can be used for any values you think are better.
(EZNEC pro only):
You'll find that even a fairly gross loss tangent doesn't make a huge difference. PTFE and PE are pretty constant over a wide range of frequencies, so the fixed values should be ok for nearly any use. Loss tangent stays relatively constant with frequency, while conductivity doesn't, so loss tangent was chosen for loss specification. For any reasonable loss tangent, the loss tangent is for practical purposes equal to the dissipation or power factor. So table values of DF or PF can be used directly. The level of loss associated with normal wire insulation generally has only a small effect on overall performance, so it will probably be most useful for unusual coatings.
Importing Wire Coordinates
Wire coordinates can be imported from an ASCII file in a simple format, either replacing or adding to the existing model. This can be used to import coordinates from another program. To import wire coordinates, select Import
Wires From ASCII file in the Wires Window Other menu, or the Control Center
Combining and importing are sometimes confused. If you want to add an existing description to your present model, see
Other Wire Considerations
Some NEC literature cautions against permitting the center of a segment to lie within the volume of another wire. This can occur when segments are short, wires have large diameters, and intersection angles are acute. I haven't been able to devise a test which shows any adverse effects from permitting this to happen, so it should be allowed to happen only if erroneous results are likely
tests for this condition, but the test can be disabled for the current description via the
selection. This choice is saved with the description.
A case was found where EZNEC produced results which were very inaccurate, and showed great sensitivity to the number of segments. This case was where a wire approached the middle of another at an angle, but wasn't connected, like an insulated guy wire at the midpoint of a tower.
Building The Model
Reliable results were obtained only by spacing the end of the "guy wire" from the "tower" by about a segment length. With slightly closer spacings, reasonable results were obtained by making sure the segment lengths of both wires were the same, and the junctions were directly across from each other, as viewed through the bisector of the angle they formed. EZNEC/4 with an
NEC-4 calculating engine may not be as sensitive, but use care with this wire arrangement, and make sure it isn't highly sensitive to the number of segments.
Some Special Cases
NEC has some difficulty in accurately modeling multiple wires joining at a very acute angle, such as with a "fan" antenna, the difficulty being greater with
NEC-2 than with NEC-4. The problem has a different cause than the
MININEC problem of "cutting corners", and quads are modeled very well by
EZNEC without special attention. However, when modeling very acutelyintersecting wires, evaluate the results carefully, particularly if a source or load is at or near the junction. It has been reported that EZNEC's
the accuracy in this situation, provided that the wires all have similar diameters. Tapering is likely to degrade the accuracy with wires of greatly
. Another method which has been reported to work is to put a separate source on each wire, rather than a single one near their junction.
NEC-2 is not able to model buried wires or conductors, so all EZNEC and
EZNEC-M conductors must be above ground. Only EZNEC/4 is able to model buried wires, when using an NEC-4 calculating engine.
The remainder of this section applies only to EZNEC/4 when using an NEC-4 calculating engine. For information about simulating buried wires with EZNEC
There are only a few restrictions on modeling buried wires, as follow:
2. Horizontal wires should be at least several wire diameters below the surface.
3. Wires can penetrate the ground (z = 0) only at a segment junction. It’s recommended that penetration be done at a wire end. That is, have the above-ground wire end at z = 0, and make the portion below ground be a separate wire, connecting to the above-ground wire at z = 0. This way, the connection won’t move, and the requirement will be satisfied, if you change the wire lengths or number of segments.
4. The velocity factor under ground is often a fraction of the velocity factor in free space. Consequently, many more segments are required for the most accurate results. EZNEC/4’s Segmentation Check takes this into account, and shows warnings or cautions if segments are too short. On the other hand, the loss associated with ground often permits coarser
EZNEC User Manual segmentation than general guidelines indicate. This is one of those cases where some experimentation, trying different numbers of segments to see where accuracy begins suffering, is required if the segment count needs to be minimized.
Closely Spaced Wires
When modeling parallel or nearly parallel wires which are closely spaced, it can be very important to align the segment junctions. That is, they should be directly across from each other. This is particularly true if the segment length is greater than the line spacing. As the segment length gets shorter compared to the wire spacing, this requirement becomes less important. When segment junctions are misaligned but need to be aligned, results can change dramatically as segmentation is changed.
The easiest way to assure that aligned parallel wires have aligned segment junctions is to give the wires identical lengths and numbers of segments. If the wires are staggered or different lengths, break them into more wires. Make the portions of the wires which are directly across from each other into separate wires of equal length and number of segments. An example of this technique is shown below, where the long wire of a J-pole antenna was broken into two wires. Wire 4 is made the same length and given the same number of segments as parallel wire 6. The upper wire is segmented to make its segment length approximately equal to the segment length on wire 4. (This is a close up view – some of the long wire isn’t shown.)
If it’s necessary to test whether alignment is necessary in a particular situation, change the segmentation of one of the wires so that the segment junction alignment changes, and note the change in results. If the change is significant, segment alignment is important.
In all cases, wire spacing should be at least several wire diameters.
To model two dipoles fed at a common point (sometimes called "crossed dipoles" -- see figure below), feed by inserting a wire between the pairs of dipole halves and place the source on the wire. The wire length should be a minimum of 0.02 wavelength, and have three segments. (See
Building The Model
Elevated Radial Systems
A number of people have showed an interest in modeling systems of radial wires placed at very low heights above ground. A system of very low wires can be used to simulate the performance of buried radials. Experiments were done comparing various modeling codes, resulting in the following guidelines:
1. The minimum recommended height for modeling ground radial systems is
0.0001 wavelength, or the diameter of the vertical wire, whichever is greater.
2. No special techniques are required if the radials are at a height of at least
0.001 wavelength and at least the diameter of the vertical wire. Ordinary segmentation can be used. Even stepped diameters don't require special attention with the NEC-2 engine in this situation. This height is recommended for simulating buried radials with NEC 2, or radials placed on the surface of the ground.
3. If the radials are between 0.001 and 0.0001 wavelength high,
should be used. The minimum segment length should be made equal to the height of the radial system. The default maximum is adequate. In the Minimum Segment Length box, enter the height of the radial system above ground. When placed on such a short wire, the source must be surrounded by equal-length segments. After tapering, combine the source wire and the one above into a single wire with 3 segments, then move the source to the center of this wire. If, for example, the original vertical wire was wire 1, with end 1 at the bottom (as in example file ElevRad1.ez), first taper all wires. Then select any coordinate of end 2 of wire 1 and enter 'W2E2' to make its coordinates the same as end 2 of wire 2. Change the number of segments of wire 1 to 3. Then delete wire 2. Finally, move the source to the center of wire 1. The result should look like ElevRad2.ez.
I don't know of any good experimental measurements of the sky-wave field strength from verticals with elevated radial systems. There are a few groundwave measurements. NEC-2 and NEC-4 both show ground-wave field strengths for elevated systems which are stronger than some measurements seem to indicate, particularly at frequencies of 3 MHz and below, so there may be some doubt about the accuracy of the signal strengths reported by
EZNEC for elevated radial systems.
EZNEC User Manual
Feedlines and Baluns
The radiation properties of a coaxial feedline can be modeled by connecting a wire of the coax shield's diameter to the point on the antenna where the shield connects. The wire is then routed (using additional wires to simulate bends) to ground along the path taken by the actual feedline. The ground path from the transmitter/receiver should be included, with wires of appropriate size. This can be done whether or not an EZNEC transmission line model is used to model the inside of the feedline. (See the
chapter for more information about using transmission line models.) The job of a
"current balun" or "choke balun" is to insert an impedance in the path formed by the outside of the shield. To model a balun, insert a load in series with the
"coax" wire (the wire simulating the outside of the coax) at the point where a balun would be placed. A good balun will have an impedance of the order of
500-1000 ohms, and may be resistive, reactive, or a combination depending on construction. Accurate modeling requires knowledge of the balun impedance at the frequency of interest. The balun reduces the current in the
"coax" wire, which means that the current on the outside of the actual coax feedline is reduced. It sometimes is necessary to insert more than one balun
(quarter-wavelength spacing is typical) to reduce feedline outside current to a low level. Coaxial feedlines connected to "unbalanced" antennas like ground plane antennas aren't immune to induction of current, either, as you can confirm with EZNEC.
Linear Loaded Antennas
EZNEC/4 gives accurate results for these antennas when using the NEC-4 calculating engines, so the following doesn’t apply to EZNEC/4 with an NEC-4 engine.
"Linear loaded" antennas (generally Yagis) are physically shortened by attaching to the elements wires which are parallel to, and spaced close to, the elements. EZNEC will not give accurate results for this type of antenna unless all the wires of a given element are the same diameter. This is due to NEC-2's inaccuracies when dealing with connected wires of different diameters and the fact that even small parasitic element errors have a major effect on the performance of a beam antenna. The stepped diameter correction used by
EZNEC is not accurate for typical linear loaded elements and will not be applied to them.
Log Periodic Antennas
An integral part of log periodic antennas is the transmission line connecting the elements. This must be included in the model, since no valid assumptions can be made about the relative voltages and currents at the element centers.
Transmission line segments between elements can be included as either wire models or as transmission line models. If wire models are used, it can be difficult or impossible to place the source in a way that fulfills all the requirements for source placement (on a wire of at least 0.02 wavelength and
Results should be tested by changing the number of source wire segments, source wire diameter, and other parameters near the source to see if the
feature should also be checked, and it can be used to correct the indicated gain to some extent. See
Building The Model the LogPer.ez example file and associated Antenna Notes file for more information.
Here’s a tip for reducing the number of segments required to model a log periodic antenna. Set the frequency to the lowest frequency of interest, then use
to segment the model. Note the number of segments in the longest element. Then resegment the other elements to each have the same number of segments as the longest element. Alternatively, you can use the highest frequency and the shortest element to determine the number of segments – the result should be about the same in either case.
The principle being used here is that at a given frequency, only a few elements have significant current. The segmentation of the other elements is less important, since they contribute little to the overall field. Using the method of using the same number of segments on each element assures proper segmentation of the active elements without using an unnecessarily overlarge number of segments on the other elements.
EZNEC is well suited for modeling multiband antennas. Keep in mind the segment length, however. Remember that as you increase the frequency the segment length increases in terms of wavelength. In general, you should double the number of segments each time you double the frequency. A bare minimum number of segments for a square loop is about four per quarter wavelength. This means four segments per side at the frequency at which the loop is a full wavelength in circumference, eight per side at twice the
about the segment length.
Issues involved with phased arrays are discussed in the section also named
NEC-2 is unable to accurately model small loop antennas. If this is attempted, a zero or negative feedpoint impedance and accompanying error message may result. NEC-4 is more tolerant, but problems might still be encountered with very small loops. Double precision versions of both engines permit smaller loops than the standard or single precision versions. Tests with a square loop in free space, one segment per wire, showed reasonably accurate results with loops down to the following minimum circumferences:
NEC-2: 0.05 wavelength
NEC-2D: 0.0005 wavelength (Available in EZNEC+, EZNEC-M and EZNEC/4 only)
NEC-4: 0.001 wavelength (Available in EZNEC/4 only)
NEC-4D: 10 -7 wavelength (Available in EZNEC/4 only)
These should be used as guidelines only, as accuracy can depend on a number of factors.
EZNEC User Manual
Stacked Yagis or other antennas can be modeled easily with EZNEC by using the Stack feature. A step-by-step example follows. In this example, we’ll stack two of the Yagis of the example file 20m5elya.ez.
In the Control Center, locate the Open
a file selection dialog box. Select 20m5elya.ez and click Open. Click here if you have trouble.
The bar at the top of the Control Center
should now read
"Five-element Yagi" -- this is the title of the antenna description stored in file
In the Control Center information window, click Units and change the units to Feet for convenience.
Click the View Ant action button to open the View Antenna Window, and the Wires line in the Control Center information window to open the
In the Wires Window, open the Wire menu and select Stack.
This opens the Stack dialog box. Note that all wires, number 1 to 55, have been entered into the first two boxes. Those are the desired wires for this example. If you had wanted to stack only some of the wires in the description, you can enter the range of wires here. You can also select the wires in the
Wires Window before opening the Stack dialog box, in which case the top two boxes won’t appear.
The third box indicates where the new wires will appear in the Wires Window wire list. 56 indicates that the new wires will be placed at the end of the list.
Let’s put the second Yagi 40 feet above the original.
Enter 40 in the Stacking distance box, and click Ok.
That’s all there is to it!
This completes the stacking process. If desired, you can change the height of both Yagis by choosing Change Height By in the Wires Window Other menu, making sure that the range of wires to change is 1 – 110. In the Control
Center you can add a ground, choose a new title, and save the description.
Vertical Antennas And Buried Radials
The effect of radials and other buried ground systems is widely misunderstood. In a typical quarter wavelength high vertical antenna, the ground has two distinct and somewhat independent effects. One is that the current flowing into the base of the antenna is matched by an equal current flowing from the ground to the other feedline conductor. This current flows through the ground and incurs loss in the process. The primary purpose of a buried ground system is to reduce this loss by increasing the conductivity of the ground near the antenna. The effect of a poor ground system is to reduce the antenna efficiency. This reduces the strength of the radiated field, but doesn’t change the antenna pattern.
The second effect is less widely appreciated but is often of much greater importance. The elevation pattern of any antenna is created by a combination of a field travelling directly from the antenna to a point in space above the horizon, and the field reaching the same point after being reflected from the ground. The relative strength and phase of these two fields are what make the lobes and nulls of the vertical pattern. As it turns out, vertically polarized waves are affected differently by the ground reflection than horizontally
Building The Model polarized waves. While horizontally polarized waves reflect nearly perfectly from even relatively poor ground (except at high angles), vertically polarized waves do not, and are affected most when reflecting at a low angle. The net effect is that the pattern of a vertically polarized antenna is profoundly modified by the ground reflection. With real ground, there is very significant loss of the low angle field. This can be illustrated by running the Vert1.ez example model, saving the 2D trace of the elevation pattern, changing the ground type to Perfect, and running again. Adding the previously saved trace to the one created with Perfect ground shows this effect graphically. Note that
Vert1 uses the MININEC-type ground model which includes no conductive loss (the first effect described above), only the ground reflection effects. The ground reflections which cause the low-angle pattern reflections take place farther from the antenna than most common radial ground systems extend, so
ground radial systems have little or no effect on the ground reflection
Please keep these two effects in mind while reading the following discussion.
Buried radials can be directly modeled only with EZNEC/4 using an NEC-4 calculating engine (see
). With EZNEC, EZNEC+, and EZNEC-M they have to be simulated. There are three ways to simulate buried radials.
because it only modifies the effect of the ground conductivity on the pattern due to ground reflection (the second effect described above), and not the conduction loss. The NEC radial model can’t be used to assess antenna efficiency, and as mentioned above, radials of reasonable length have little effect on the ground reflection. And the NEC radial model tends to give an erroneous estimation of the effect of the radial field on ground reflection due to the simplistic way it evaluates reflections.
The second approach is to model buried radials by substituting radials just above the ground surface. This does a moderately good job of predicting the ground system efficiency as well as whatever pattern modification (typically
must be used. See
, which models the ground reflection but not the conductive loss, and simply add a resistive load at the feedpoint to simulate the radial system loss resistance. The NEC radial model can be used in addition if desired. Approximations for the amount of resistance for a given number of radials can be found in Chapter 8 of The
ARRL Antenna Book. (This reference gives total resistance for a quarter wave vertical, so subtract 36 from the values shown to use as the ground system resistance.) These are of course approximate. Direct measurement is better yet. If you have an antenna analyzer or similar way to measure your antenna’s feedpoint resistance, follow this procedure:
1. Measure the antenna’s feedpoint resistance. If you can only measure impedance, the resistance will be the impedance at resonance.
2. Add a load to the model at the feedpoint and adjust its value until the feedpoint resistance matches the value you measured.
EZNEC User Manual
Wire Grid Modeling
EZNEC pro programs (EZNEC-M and EZNEC/4) include a feature to automate the process of creating flat, rectangular wire grids. Even if you’re
section gives general guidelines for wire spacing and diameter.
Before beginning a wire grid model, you should estimate the number of segments which will be required. The approximate number required, based on
0.1 wavelength spacing, is 220 * A, where A is the area in square wavelengths. Some compromises might have to be made to avoid exceeding the standard program’s segment limit. You can see that the number of segments required for a given physical size of object depends on the wavelength at which the analysis will be done. A car, for example, can be modeled as a pretty simple wire frame at HF. But even just a roof will strain or exceed the ability of the standard EZNEC program at UHF.
Be sure to take advantage of EZNEC’s
features for creating your wire grid. You’ll find that with a little practice, wire grid creation can go pretty quickly. You can also re-use wire grids by taking advantage of the
model can most easily be done by changing the frequency with the
option selected. Don’t forget to save your description before you take each step, in case a mistake is made. A group modify error can be very time consuming to recover from if you haven’t made a backup copy!
Always remember that wires must contact and connect only at their ends, so you shouldn’t cross wires in the grid or elsewhere.
The following remarks apply only to EZNEC, EZNEC+, and EZNEC-M, and to
EZNEC/4 only if the NEC-2 engine is chosen. NEC-4 is relatively free of the
, so this does not apply to
EZNEC/4 using an NEC-4 calculating engine.
Yagi antennas with full size (near half wavelength) elements can be accurately modeled with EZNEC. When made from telescoping tubing, or other materials where the element doesn’t have a constant diameter over its
However, it can’t do this correction for elements which aren’t nearly a half wavelength long (i.e. elements which contain loading coils or traps, or which are “
element diameters are constant. The overall performance of these antennas can still be determined, but there will be a frequency shift in the results from the actual frequency where that performance will occur.
When modeling a Yagi with near half wavelength elements, it’s important to follow the rules outlined in
EZNEC to apply the correction. It’s easy to make an error which disables the correction for a given element, so EZNEC provides a method to make sure the correction is being applied as it should. This is the stepped diameter correction display, and its use is described in Using The Stepped Diameter
Correction Display . You should consult this display each time you design or modify a Yagi model to make sure all elements are being corrected.
Information about modeling stacked Yagis can be found in the
Advanced Wire Features
Advanced Wire Features Introduction
Advanced features are available for creating and modifying antenna
are available only in the
EZNEC pro programs EZNEC-M and EZNEC/4. The remaining advanced features are available in all program types.
The NEC “card” feature is in the Wires Window Other menu; the others are in the Create and Wire menus.
To create a loop, open the Create menu in the Wires Window and select
Loop. Although the dialog box might appear complex, it’s actually quite simple to use. Most items are self-explanatory. The wire diameter can be entered either as a value, or as a wire gauge, just like wires in the main wire entry grid. In the Loop Size frame, you can define the loop size in any one of three ways, by circumference, side length, or the approximate diameter (the diameter of the circumscribed circle). As you enter a value, the remaining two are calculated for you. You can position the loop anywhere, and can orient it with its axis in any of the three principal directions.
You can use the loop resizing feature (Wires Window, Wires menu, Change
Loop Size) to change the size of any polygonal loop. The first step is to specify the loop, by selecting the wires in the Wires Window or View Antenna display. Or you can click the selection before you select wires, in which case you’ll have to choose a set of wires in numerical sequence. The selected wires have to be connected in a loop, of course, and no wires can be connected to the loop other than the wires comprising the loop. If you’ve recently created a loop, its wires will be entered as an initial choice. The buttons and text box at the bottom of the dialog box allow you to modify the size with any of three different operations, on any of three loop size measurements.
EZNEC’s automated radial creation feature is a convenient way to make a group of radial wires. This feature is accessed from the Wires Window, Create menu, Create Radials selection. When this selection is made, a dialog box appears which prompts for a range of “prototype” wires. To make a simple set of radials, you should first create a single radial wire. End 1 of the radial wire should be where you want the center of the radials to be. Enter its number as both the first and last wires in the prototype group. In the bottom box, enter
EZNEC User Manual
Ok. The radials will be created, fanning out evenly around end 1 of the prototype wire. A vertical wire can’t be used as the prototype.
More complex radial structures can be made by specifying a group of wires as the prototype radial to be copied. A prototype group of wires has to be sequentially numbered (that is, you can’t use wires 1, 2, and 4 as the prototype group, for example) and must be connected end 1 to end 2. This group of wires will then be duplicated, centered around end 1 of the first wire in the prototype group. The first wire in the group can’t be vertical, since this would result in the first wire of the copies all occupying the same space.
The helix creation dialog box opens when you select Helix from the Wires
Window Create menu. Most entries are self-explanatory. In the
Turns/Spacing/Length frame, you must choose any two measures for the length; the third will be calculated and entered automatically. If you check the
“Extend ends to helix axis”, an extra wire will be created on each end of the helix, extending to the helix axis. Only plain cylindrical helices are created.
Turn spacing should be at least two wire diameters, and ideally several wire diameters. A few experiments, making use of the Undo feature, will quickly get you acquainted with the various features.
Wire Grid Creation
The automated wire grid creation feature is available only in EZNEC pro programs (EZNEC-M and EZNEC/4). For information about manually creating
A wire grid is a good way to simulate a flat, solid, conductive surface such as a metal roof or car top. A wire grid looks like a screen, with each side of each screen hole made from a wire. (See the diagram in the
In general, the best implementation is for each side of each hole to be a single one-segment wire. Although wire grid modeling is an art in itself, a few general rules have evolved which give good results for most situations. One is that the size of the holes (that is, the wire spacing) shouldn’t exceed about 0.1 wavelength. Some studies have indicated that a coarser structure is adequate far from the source, where current is lower. The same general rule should be followed here as for elsewhere in any model, that segmentation needs to be finer when the current changes rapidly from one segment to another. Another general practice is to make the surface area of the wires equal to the area of the surface being modeled. This requires larger diameter wires than normally used (diameter equal to the spacing divided by pi), but usually produces the best results.
EZNEC provides an automated method which greatly simplifies the creation of wire grids. Wire grid definition is done with a dialog box opened by selecting
Create Wire Grid from the Wires Window Other menu. It requires you to specify the coordinates of three corners of the grid, then EZNEC will do the rest. You can adjust the wire spacing and diameter if you wish. But the default values, which follow the rules described above, are generally adequate.
The Wire Grid Creation dialog box is opened by choosing Other/Create Wire
Grid in the Wires Window.
In the dialog box, note the rectangular area with “GRID” shown in the center, and with “Side A” and “Side B” labeled. This represents the physical grid. Sets
Building The Model of text boxes labeled “X”, “Y”, and “Z” are placed close to the corners of the grid which their coordinates represent. That is, the coordinates on the upper left are for the upper left corner of the grid (the junction of Side A and Side B), and so forth.
The approximate number of wires to be created is shown near the lower left. If insufficient information has been entered to calculate the number of wires,
“Data incomplete” appears.
This is normal.
X, Y, Z (three sets) – In these boxes, enter the coordinates of three corners of the grid. Note that it’s possible to create a parallelogram as well as a rectangle by the appropriate choice of coordinates. The units of the coordinates are the current units chosen for EZNEC, which is shown below the lower left set of coordinates.
Incl Side A Wires – If this box is unchecked, the wires along Side A will be left off. This option is used when connecting two wire grids, to avoid creating duplicate wires at their junction.
Grid Spacing – Allows you to specify the spacing between wires (the width of the holes). The default value of 0.1 wavelength can be easily selected by checking the box.
Wire Diameter – Allows you to specify the wire diameter. The default value of spacing/pi, which results in wire area equal to modeled surface area, can be selected by checking the box.
NEC 'Card' Entry
This feature is available only in EZNEC pro programs (EZNEC-M and
EZNEC pro permits the direct entry of several powerful NEC “cards”: GM
(coordinate transformation), GR (generate cylindrical structure), GS (scale structure dimensions), and GX (reflect structure in coordinate planes). These operations make it possible to make replicas of, rotate, translate, or scale the whole structure or a group of wires, or combinations of these.
The feature is accessed from the Wires Window Other menu, selection
Execute NEC ‘Card’. At the top of the dialog box is a brief explanation of what the function does and what each parameter is for. NEC “card” nomenclature is generally followed, but there are a couple of important differences. One is that the range of wires to operate on can be chosen. Another is that linear values are in current EZNEC units rather than always being in meters. If you want to enter values in meters, first change the EZNEC Units from either the Control
Center Units line or the Wires Window Other menu.
Stepped Diameter Correction
The following information applies only to the NEC-2 calculating engine, which is the only choice for EZNEC and EZNEC-M. This problem doesn't occur when using NEC-4 with EZNEC/4 for calculations unless there are extreme differences in the diameters of connected wires. In general, if you
EZNEC User Manual have EZNEC/4, you should use an NEC-4 calculating engine whenever wires of different diameters are connected.
NEC-2 is known to be inaccurate in modeling connected wires having different diameters. (Note: This is sometimes called being "tapered". It shouldn’t be confused with EZNEC’s
.) The problem gets worse as the segments near the junctions get shorter and as the diameter difference gets larger. The error is small enough that it's not important for many applications, such as evaluating a tower top-loaded with a beam. However, if the stepped diameters are on a parasitic element or exceptionally high-Q antenna, the inaccuracy can cause significantly bad results. EZNEC incorporates a method developed by Dave Leeson and described in his book
Physical Design of Yagi Antennas (ARRL, 1992) for calculating an equivalent wire of constant diameter to replace a group of wires of different diameters.
The method is valid only under a narrow range of circumstances, however, and EZNEC will apply it only under those circumstances. The requirements are that:
- There must be at least two wires in the group.
- At least two of the wires must have different diameters.
- All wires in the group must be collinear (in a straight line).
- All wires must be connected to each other.
- Both ends of the group must be open, or one end open and one connected to ground.
- The group must be nearly resonant (within about 15% of half-wave resonance if both ends are open, or within about 15% of quarter-wave resonance if one end is grounded).
- Only one source is permitted in the group, and it must be at the center if the ends are open, or at the bottom segment if the group is grounded. If the ends are open and the center of the group is a wire or segment junction, the source must be a split source. If the group is grounded, the source must not be a split source.
- The rules for loads are the same as for sources, except that two equal loads must be used wherever a split source would be used.
- A single transmission line can be connected to the group. If the ends of the group are open, the center of the group must be a segment center -- not segment or wire junction -- and the transmission line can be connected only to this segment. If the group is grounded, the transmission line can be connected only to the bottom segment.
These criteria apply to typical Yagi elements made from telescoping tubing, one of the most demanding cases where the correction is needed. The correction won't be applied to a gamma match, another sensitive application, so attempting to model gamma matches isn't recommended if very accurate results are required.
A bright notice will appear on the EZNEC screen during calculation when the stepped-diameter correction is being used for one or more groups of wires.
You can see exactly what the substitutions are from the Wires Window by selecting Other/Show Stepped Dia Correction. (See
The correction can be disabled from the Options Menu if desired, but this isn't recommended.
Building The Model
In situations where wires of different diameters are connected but EZNEC's stepped-diameter correction doesn't apply, a technique can be used to minimize the error. This is to use the minimum number of segments possible, and do not use segment length tapering. (Exception: wires very near ground.
. The accuracy of NEC-2 is worst in the presence of stepped diameters when the segment length/diameter ratio is small. Especially when confronted with a large difference in diameters, the best accuracy will be obtained if you use the automatic segmentation feature in the Wires Window, and select (M)in. recommended. The accuracy is still not likely to be good enough for accurate modeling of parasitic elements if the built-in correction can't be applied.
The inaccuracy of NEC-2 in the presence of large steps in diameter typically shows up as an incorrect reactance. If you design an antenna with parasitic elements having connected wires with largely differing diameters, EZNEC will give an accurate idea of the antenna performance. However, it will show the performance occurring at not quite the correct frequency. When you actually build the antenna, you can expect the predicted performance, but may need to adjust parasitic element lengths slightly to achieve that performance at the desired frequency. For example, if EZNEC shows your "X-beam" to have a gain of 6 dBi, front/back ratio of 20 dB, and feedpoint SWR of 1.5:1 at 14
MHz, you might find when you build it that the front/back ratio is much worse than predicted at 14 MHz but is very good at 14.5. In this case, you would need to lengthen the parasitic element until you get the best front/back ratio at
14 MHz. The beam will then have very nearly 6 dBi of gain and 1.5:1 SWR at
The stepped diameter correction display shows you exactly what substitutions
EZNEC has made to correct for connected wires of different diameter. One of its most important uses is to make sure that all the elements of a Yagi or similar antenna are being corrected.
The stepped diameter correction display is shown by first opening the Wires
Window, then choosing Show Stepped Dia Correction from the Other menu.
One of two indications will be shown for each wire. If coordinates and diameter are shown for the wire, that wire is being corrected, and the coordinates and diameter are those of the wire being substituted by EZNEC.
Notice that the diameter of all substituted wires in an element are the same, and that the element length has been modified slightly. These are the consequence of the substitution process, and will give accurate results. The other possible indication is a message, spread out over several columns, briefly telling why the “group” (of connected wires) hasn’t been corrected. All the elements in a
show as not being corrected, you should return to the ordinary Wires Window display by selecting Show Stepped Dia Correction from the Other menu (to turn it off), fixing the problem, and checking again until all wires are being corrected.
EZNEC User Manual
Sources are EZNEC components which represent places where power is applied to an antenna. Every EZNEC model must contain at least one source.
NEC is notoriously sensitive to source placement, and careless placement can lead to subtle errors in calculation results. Please read the following section carefully so you’ll avoid these problems.
Sources are connected in series with the wire (as though the wire were broken and the source inserted). A voltage or current source appears in parallel with a transmission line connected to the same segment, and in series with a load in the same segment. Technically, a source is distributed over the entire segment at which it's connected; you can envision it as being inserted at the center of the segment. The positive terminal of the source always points to end 2 of the wire, so a source with zero phase angle will produce current which flows from end 1 to end 2 of the wire. These connections are dictated by the structure of NEC.
The restriction of source placement to segment centers prevents placing a source at a wire junction. Junction placement is sometimes desirable, for example in a vee type antenna. EZNEC includes special source types to allow you effectively place sources at wire junctions when required.
If you want to keep the total power into the antenna constant, you can select
Power Level from the
menu and specify the desired power. When this option is used, the specified source voltages and/or currents of multiple sources will be maintained in the specified ratio, but their absolute values will be adjusted by EZNEC to furnish the specified total power to the antenna. If a single source is used, its value will be adjusted as necessary to provide the specified power. This feature is useful when absolute values of field strength (near or far field), voltages, currents, or power loss need to be known for a given power input. There is no way to control the power sent to an individual source if the model contains more than one source, other than manually adjusting the source voltage or current until the desired power is obtained. I’m not aware of any application for which this would be necessary or desirable.
Four source types are available with EZNEC: voltage, current, split voltage, and split current. (NEC has additional types which aren't implemented.) When you specify a "split" source, EZNEC actually creates two sources, and places them on adjacent segments closest to the position you specified. Split sources are shown in the View Antenna display as two sources, but appear everywhere else as a single source. Split sources are included so you can place sources at wire junctions, such as on an inverted vee antenna. See
for more information about using conventional sources.
If the antenna contains only one source (a split source is counted as one source), it makes no difference whether a current source or voltage source is
Building The Model used, unless you have a need to know the field strength when a specific voltage or current is applied to the antenna. However, the choice can make a profound difference if multiple sources are used. Voltage sources will always maintain the specified voltages, and therefore the specified ratio of voltages, regardless of the impedances they encounter. Similarly, current sources maintain the specified currents and current ratio. One of the most common applications for multiple sources is in modeling phased arrays. Most arrays are designed to work with a specified current ratio (because the fields produced by the elements are proportional to their currents), so current
for more information about using multiple sources.
Using The Sources Window
Open the Sources Window by clicking on the
Sources line or the button to its left.
Specifying the Source Position
Specifying the Amplitude and Phase
When a single source is used, the amplitude and phase will make no difference to the pattern, gain, or impedance. Only the source and load voltage, current, and power, and absolute field strength (in V/m or A/m) will change. If a
has been specified, even these won’t change as you change the source amplitude and phase. Amplitude and phase are most important when multiple sources are used, in which case their relative values are what count. See example files Cardioid.ez and 4Square.ez which illustrate the use of multiple sources.
To add any number of sources, select Source/Add. Enter the number of sources in the upper box. If the lower box is left unchanged, the new source(s) will be added below the existing sources. If desired, you can specify other locations for the new source(s) by entering the position in the lower box.
To add a single source, you can also simply type the location, magnitude, phase, and type in the add row, then press <Enter> or click on another row of the grid. Any cells left blank will be filled with duplicates of the values for the last source.
Specifying the Source Type
Move the cursor to the right-most column. Click on the arrow at the right of the cell to open the pull-down list. Choose the desired source type from the list, or
for more information.
Deleting, copying, and moving sources require first selecting which ones are to be operated on. In addition, sources can be selected before starting
. To select a source, click on the button on the left side of the appropriate row. The selected source will be highlighted. To select additional sources, hold <Ctrl> down when clicking the button. To select a group of sources, select the first source, then hold <Shift> while clicking the last source in the group.
EZNEC User Manual
The current source, or selected sources, can be deleted by pressing the
<Delete> key. Alternatively, a sequential group of sources can be deleted by selecting Source/Delete and specifying which to delete.
Copying and Moving Sources
To copy or move sources in the list, first select the sources as described above. Then select Source/Copy or Source/Move Source(s) in List. You’ll be asked for the location in the list for them to be put. You can also select
Source/Copy or Source/Move Source(s) in List before selecting sources, in which case you’ll be asked for a range of source numbers to copy or move.
Sources can be modified individually, or if desired, a group of sources can be modified at the same time using the
feature. The procedure is the same for both cases, except that to modify a group of sources, Group
Modify must first be activated.
Basic modification of one parameter is done simply by entering the new value in the cell, then pressing <Enter> or clicking on a cell in another grid row.
Source Placement Precautions
NEC is very sensitive to source placement, and subtle errors can result if sources are placed incorrectly. Whenever possible, you should try to follow these rules:
1. The source shouldn't’t be placed on a wire which is shorter than about
0.02 wavelength, particularly if adjacent wires connect at an angle.
2. The segments adjacent to the source segment should be the same length and diameter as the source segment. If placing it on a short wire, it’s good practice to give the wire three segments to insure this condition.
3. Segments beyond the adjacent segments shouldn’t be drastically different in length and diameter from the source segment and segments adjacent to the source segment.
4. Sources shouldn’t be put on a wire which is part of a small loop.
5. It’s usually better to use a split source at wire junctions than to insert a short wire containing the source.
Rules 1 and 2 can be broken when a short wire is used only for connecting a source to a transmission line. In this case, a very short one-segment wire is generally adequate.
It’s often not possible to follow all these rules and still accurately model the antenna, so compromises sometimes have to be made. One of the most powerful tools for evaluating source placement is EZNEC’s
feature. Whenever a 3D plot is calculated, EZNEC calculates the “average gain” by integrating the total radiation pattern power and dividing it by the power furnished by the sources. This is reported at the bottom of the Control
Center form. Source placement problems are often indicated by average gain values significantly different from one when no loss is present, and source placement can be modified to bring the average gain as close as possible to one. Note (EZNEC/4 only): Average Gain can’t be used to evaluate source placement if the model includes buried wires.
To use Average Gain to test source placement:
Building The Model
1. Save the current description.
2. In the Control Center, choose Plot Type/3 Dimensional.
3. If any Real ground type is specified, change the Ground Type to
4. If any loads are specified, set their resistances to zero, or delete them.
5. In the Control Center, set the Wire Loss to Zero.
6. Do a far field plot. Note the average gain reported at the bottom of the
Control Center form. If you see “Model contains loss” to the right of the average gain, review the steps above and make sure all sources of loss have been removed. The average gain won’t be meaningful for this purpose if there is any loss in the model, indicated by the “Model contains loss” note.
If the 3D pattern has very narrow lobes, it might be necessary to reduce the step size for greater accuracy. However, 5 degrees is generally adequate.
The field strength (and gain) error is approximately equal to the deviation of the average gain from one (zero dB). That is, if the reported average gain is
+2 dB, the gain and field strength reported by EZNEC is about 2 dB greater than reality. Source placement should be modified to make the average gain as close to one (zero dB) as possible. If full correction can’t be made, the average gain in dB should be subtracted from the field strength results. This correction method might be considerably in error if the model contains multiple sources, but should be reasonably accurate for a single source.
7. Note the modifications you made to improve the source placement. If modifications were extensive, it’s probably easiest to restore the loads, wire loss, and ground type to the lossless model. If minor, it might be easier to open the saved original file and apply the source placement modifications to it.
Even though sources appear in the View Antenna display to be placed in the center of a segment, the source is actually distributed over the entire segment. If source placement is critical (for example, in a base-fed half-wave vertical or center-fed full-wavelength dipole if impedance is important), the length of the segment containing the source can become important. The shorter the source segment is made, the more closely it imitates one connected at a single point. A simple test can show if this is important. Divide the wire containing the source into a reasonable number of segments, remembering to follow the rules at the top of this section. Run the program and note the results which are important to you (such as gain, or impedance).
Move the source over one segment and repeat. If the results change more than you're willing to accept, you'll need to minimize the length of the source
Placing Sources On Segments
All sources have to be placed on segments. EZNEC’s split sources mimic single sources placed at a wire or segment junction, but they’re really made from two conventional sources placed on the segments adjacent to the chosen junction. Connecting a source to a transmission line requires that a wire be created for both the source and transmission line to connect to. No more than one source can be placed on a given segment.
The source location is specified by wire number and location on the wire. In the Sources Window, enter the wire number and the percentage of the way
EZNEC User Manual from end 1. For example, to place a source on end 2, enter 100 for the percentage from end 1. A shortcut is available for end or center placement. In either of the columns in the Specified Pos. group, you can enter ‘W#E#’ where the two #s represent the wire and end numbers. To place a source at the center of the wire, you can enter ‘W#C’. EZNEC places the wire as close as it can to the specified position, and tells you the placement location in the Actual
Use standard (non-split) sources whenever possible, and use split sources only when it’s necessary to put a source at a wire junction.
Tip: If you want to place a source on the center of a wire, give the wire an odd
number of segments.
Placing Sources At Wire Junctions
Conventional EZNEC sources have to be placed on a segment, so simulating a source at a wire junction requires special techniques.
The preferred method is to use EZNEC’s split sources, which are intended for just this purpose. When you specify a split source, EZNEC actually creates two sources, and places them on adjacent segments closest to the position you specified. Split sources are shown in the View Antenna display as two sources, but appear everywhere else as a single source. Split sources are positioned just like conventional sources, except that the position chosen by
EZNEC will be the closest segment junction or wire end rather than the closest segment center to the position you specify. When using split sources, make sure that any load placed on the segment containing one source has a corresponding load on the segment containing the other, and avoid putting transmission lines on segments with split sources. Split sources can't be placed at a multiple-wire junction, and shouldn’t be placed where the segment length or wire diameter is different for one source than the other. Split sources also can’t be placed on an open wire end, because one of the actual sources making up the split source would be off the wire altogether.
The N4PCLoop.ez and BYVee.ez example files illustrate the use of split sources.
Another way to put a source at a wire junction is to insert an additional short wire at the junction, and place the source on it. This technique would be used for multiple dipoles with a common feedpoint, for example. But care has to be
before doing this. Sometimes it’s helpful to taper the segment lengths away from the junction, using EZNEC's
Connecting Sources to Ground
A common question is how to connect one end of a source to ground. The answer is to connect a wire to ground (by giving one end a zero z coordinate) and place the source in the bottom wire segment. Example description file
Vert1.ez illustrates this method. Wires should only be connected to Perfect or
Real, MININEC-type grounds. See
for more information.
Building The Model
Using Multiple Sources
You have to take some precautions when using multiple sources in an antenna to avoid currents which are 180 degrees from what you intended. In phased arrays of parallel wires, make sure that end 1 of the wires are all facing the same direction (for example, all wire end 1's of a vertical array connected to ground). Reversing a wire will reverse the effective polarity of all sources in that wire because positive current from a source is always directed toward end 2, and positive current is defined a current flowing toward end 2.
An ambiguity can arise when placing a split source at a wire junction because the polarity can depend on which wire the source "belongs" to and which way this wire is facing. A split source placed on a junction of two wires "belongs" to the wire specified as its desired position. Therefore, it will be placed with the positive terminal facing end 2 of the specified wire. Ambiguity can be avoided by making the wires face the same direction by connecting them end 1 to end
2. Whenever you use multiple sources in any antenna other than simple, parallel wires, it's highly recommended that you look at the currents in the wires and make sure they're really flowing in the direction you thought. See
EZNEC allows you to model phased array feed systems provided that they’re made exclusively of transmission lines, and provided that the transmission lines don't interact with the antenna as wires. (EZNEC doesn't model coupling to transmission lines.) Example description files CardTL.ez and 4SqTL.ez are examples of this. EZNEC doesn't have any provision for modeling networks made from components other than transmission lines. To investigate various possible patterns, instead of modeling transmission lines, place a current source at each element's feedpoint and vary the element currents by changing the source magnitudes and phases. A very valuable capability of
EZNEC is to tell you what the element feedpoint impedances are when an array is correctly fed. This information is required to design a feed system to produce the desired current ratio. To determine the impedances, insert current sources at the feedpoints, with the currents being in correct ratio.
Clicking the Control Center Src Dat (Source Data) action button will tell you the feedpoint impedances. 4Square.ez and Cardioid.ez are examples of phased arrays fed with multiple current sources.
Loads are EZNEC components which represent a lumped impedance that can be inserted into a wire. Like sources, these are easy to place with EZNEC, and appear in series with the wire. Like sources, loads are actually distributed along the entire segment, but conceptually can be regarded as being at the segment center. Loads always appear in series with a source, transmission line, or other load placed on the same segment. There is no direct way to place a load in parallel with a source, transmission line, or another load.
Loads are useful to simulate loading coils, capacitors in capacitive-loaded
EZNEC User Manual antennas, traps, and losses. They can be specified in three different ways: as an impedance consisting of resistance and reactance (R + jX), as an RLC combination, or as a quotient of Laplace transform polynomials. These are
Loads are entered and modified via the Loads Window. Operation varies some with the load type chosen, and detailed information about using the
Loads Window with each type is given in
Reference section. Load placement is identical to placement of sources, as
In critical applications, the same restrictions should be applied to loads as to sources regarding placement. See
. I don’t know of any way to assess load placement problems with the Average Gain feature as is done with sources, so the only way to spot problems is to modify placement and observe how much the result changes.
EZNEC loads do not radiate, except that the segment the load is placed on does radiate like any other segment.
Three different load types are available, R + jX (resistance and reactance),
RLC, and Laplace. Each has its advantages, as outlined below. Note that all loads in a model must be the same type, so a compromise sometimes has to be made in choosing which type to use.
R + jX – This load type is the fastest and simplest to use. You just specify the resistance and reactance. Because the impedance of an R + jX load doesn’t change with frequency while a real load (if it contains reactive components) does, the R + jX load type is most useful for frequency independent loads
(i.e., pure resistances) or for analysis at a single frequency or a narrow range of frequencies.
RLC – This load type is most convenient if you know the values of R, L, and C of the load you’re trying to model. Not all components have to be present, so this type can also be used for modeling any combination of the three, including a single R, L, or C. A powerful feature of this model type is that the resistance can be made to vary with frequency to simulate skin effect loss
(such as an inductor exhibits) or insulation loss. Each load’s resistance can be set independently, so you can make some vary and some not if you wish. You enter RLC loads directly as values of R, L, and C for this load type, rather than as resistance and reactance. The impedance of the combination varies realistically with frequency. The disadvantage of this load type is that currently only three connections are supported, series, parallel, and “trap” (series RL with parallel C). The “trap” model is useful for modeling inductors as well as traps or other parallel resonant circuits.
Laplace – This load type can be used only by people who understand how to calculate the Laplace polynomial quotient which represents a circuit.
Explanation of this is beyond the scope of this manual, and interested readers should consult a text on circuit analysis for more information. The advantage of this load type, for those who are able to use it, is that relatively complex combinations of components (that is, R, L, and C) can be modeled. The impedance of a Laplace load varies with frequency, although the resistance can’t be made to vary with frequency as in the RLC load type.
Building The Model
More detailed information about using the Loads Window to specify the
Placing Loads On Segments
The procedure for placing a load on a segment is identical to placement of
Placing Loads At Wire Junctions
Like a source, a load is distributed over a segment, so conceptually can be regarded as being placed at a segment center. Direct placement on a segment or wire junction isn’t possible, but it can be simulated with two loads.
To simulate a load at a wire junction, split it into two equal loads of half the value and place each one on the adjacent segment. When EZNEC spots identical loads on segments adjacent to a wire junction, it shows voltages, currents, impedances, and losses of the combination as well as the individual
Loading coils frequently have a significant amount of loss which should be included in the model. Measurement is the best way of determining the loss, but even a guess may be adequate. Air-wound inductors typically have Q's in the range of 200-400 or so. This means that you can estimate the equivalent series R as about 1/200 to 1/400 the reactance. If using this range of values impacts your result, you might want to make a measurement or better estimate of the Q.
A trap has a primary resonance at only one frequency, but still represents a significant impedance at other frequencies and on other bands. So a trap model has to be reasonably accurate over the entire range of antenna operating frequencies. (Or at least over the range being modeled.) The only way to accurately model a trap is either by measuring its impedance at each frequency of interest, or by knowing the equivalent L, C, and R components, and how R varies with frequency. These in turn must be measured unless you can talk the manufacturer out of this information (or have constructed the trap yourself out of known components). Traps frequently will cause a couple of dB loss at one frequency or another, so failure to include loss resistance will lead to overly optimistic results. The trap RLC model, as its name implies, is particularly useful for modeling traps.
Using The Loads Windows
Load Types And The Loads Window
The Loads Windows are where impedances are placed on the wires in the model. Loads can be specified in three different ways, as R + j X, RLC, and
Laplace types. The types can’t be mixed, so all loads have to be of the same type. The appearance and operation of the Loads Window depends on which load type you’ve selected.
EZNEC User Manual
The load type is saved with the description file, so when you first open the
Loads Window (from the Control Center), it will reflect the type of load specified for the current description. You can change the load type at any time from the Loads Window by selecting “Change Load Type” from the Other menu. NOTE: When you change the load type, all existing loads are converted to the new type if possible. Most conversions are not reversible, so if you change back to the original load type, loads are likely to be different than the originals. For example, if you specify a parallel RLC type load and change to the R + j X load type, the impedance of the load will be calculated and entered as the R + j X impedance. If you change back to the RLC load type, the R + j X impedance will be converted to a series RL or RC circuit. So it’s recommended that you save the description before changing load type if you have defined any loads and if there’s a chance you may want to change back.
Load position specification, and operations such as adding, deleting, and
The R + j X Loads Window
R + j X type loads are expressed as a series combination of resistance (R) and reactance (X). The impedance of R + j X loads does not change with frequency.
The load number column and specified and actual position columns function
The impedance of each load is entered as resistance (R) and reactance (X) in the appropriate columns. The value of R cannot be negative.
The RLC Loads Window
RLC loads are defined as a combination of R, L, and C components. They can be connected in series, in parallel, or as a "trap" connection, as shown below. R can optionally be made frequency dependent.
Building The Model
The load number column and specified and actual position columns function the same as for the
appropriate columns. EZNEC will calculate and use the impedance of the
RLC combination as required.
The rightmost column is used to select the type of RLC circuit, Series,
Parallel, or Trap. This selection can be made by entering “S” or “Ser” for
Series type, “P” or “Par” for Parallel type, or “T” or “Trap” for Trap type. Or you can click the cell to activate the drop-down list arrow, click the arrow to open the list, then make the selection.
RLC Load Types and R, L, C Columns
Series Type RLC Loads
The R, L, and C are connected in series. Any of the three components can be replaced by a short circuit by entering “0” (the number zero), “S”, or “Short” as the value, or by leaving the grid cell empty. Note that there is no way to specify a zero capacitance (open circuit) in a Series type RLC load; an entry of zero will be interpreted as a short circuit.
The resistance of typical wire and tubing increases as the square root of frequency, so the resistance can be made to vary in this way for the Series
RLC type. See “R Freq Column”, below.
Parallel Type RLC Loads
The R, L, and C are connected in parallel. Any of the three components can be replaced by an open circuit by entering “0” (the number zero), “O” (the letter O), or “Open” as the value, or by leaving the grid cell empty. Note that there is no way to specify a zero resistance or inductance (short circuit) in a
Parallel type RLC load; an entry of zero will be interpreted as an open circuit.
The parallel model is frequently used for relatively high impedance loads, where dielectric loss often dominates. Consequently, the frequency dependence of R is that of typical dielectrics; that is, it decreases in inverse proportion to frequency. See “R Freq Column”, below.
Trap Type RLC Loads
This load type can be used to represent objects other than traps. For example, it can be used to model an inductor, accounting for the frequencydependent conductor resistance and shunt capacitance. It was called a Trap type simply because this is one of the common applications. The Trap type
RLC load consists of a resistance R and inductance L in series. The series combination is in parallel with a capacitance. The series RL circuit is a reasonable model of a real inductor, and the shunt capacitance can represent stray inductor capacitance, a physical capacitor, or a combination of the two.
The frequency dependence of R is the same as for the Series type RLC load.
In this load type, entry of zero for R or L results in that element being replaced with a short circuit. Entry of zero for C results in replacement with an open circuit. As for the other RLC load types, the short circuit can also be created by entering “S” or “Short”, and the open with “O” or “Open”.
R Freq Column (all types)
The “R Freq” column is the frequency at which the resistance has the value specified in the R column. If any value other than zero is specified as the R
Frequency, the resistance will vary with frequency as described above.
EZNEC User Manual
(Series resistance – Series and Trap types -- changes in proportion to the square root of frequency. Parallel resistance – Parallel type – changes in inverse proportion to the frequency.) Enter zero in this column to keep the resistance fixed with frequency. The current frequency can be conveniently entered by clicking the cell to activate the drop-down list arrow, clicking the arrow, then clicking the highlighted frequency value which appears.
The Laplace Loads Window
Laplace loads are impedances which are defined as Laplace coefficients. This load type is most useful for representing complex combinations which can’t be represented by other load types. Any combination of R, L, and C up to fifth order can be represented with Laplace type loads. Because Laplace type loads represent R, L, and C components rather than fixed impedances, the impedance varies with frequency as appropriate for the components comprising the load. However, R cannot be made to vary with frequency as with RLC type loads. Do not use this load type unless you are familiar with the
use of Laplace transforms, the explanation of which is beyond the scope of
The load number column and specified and actual position columns function
Impedances are entered as Laplace coefficients, with zero to fifth order from left to right and numerator on the top and denominator beneath. At least one denominator coefficient must be non-zero.
Using Transmission Lines
About Transmission Lines
There are important differences between the NEC transmission line models used by EZNEC and real-life transmission lines, so there are several things you have to be aware of in order to use them effectively.
First, the EZNEC transmission line models are lossless. They have no attenuation and are not accurate models for lines with significant loss.
Second, the only parts of the transmission line model which exist as far as the program is concerned are the ends. Imagine the model as being two sets of portable terminals which can be placed on any two segments. The current and voltage at one set of terminals relative to the other is just the same as though there were a transmission line connected between them. But the transmission line can be any length you specify, including longer or shorter than the physical distance between the "terminals". Although the terminals are accessible to connect to the antenna wires, the transmission line itself is
"somewhere else". So, unlike real transmission lines, EZNEC transmission line models don't interact with the antenna fields. That is, the currents in the model's two conductors are always equal and opposite, so the line doesn't radiate or have current induced by coupling. In many real-life cases, a transmission line does interact with the antenna fields, and becomes a radiating part of the antenna. This can be caused by coupling to the antenna due to non-symmetrical placement of the feedline, or by presenting the feedline with an unbalanced source or load. EZNEC transmission line models
Building The Model are suitable for modeling symmetrically-placed balanced lines such as a logperiodic feed distribution line or W8JK phasing line. They aren't suitable for modeling, for example, a quarter-wavelength phasing stub extending outward from a collinear antenna, since the stub wires in a real collinear antenna have unbalanced currents and will radiate. Coaxial lines laid on the ground, such as in a vertical phased array feed system, may carry current on the outside just like a ground radial wire. In many cases this can be ignored and the
EZNEC pro model used. A coaxial cable with field interaction (that is, with current flowing on the outside of the shield) can be modeled with a combination of a wire and transmission line model as described in
be modeled as wires.
The third thing to realize about EZNEC's transmission line models is that all ends which aren’t specified as a shorted or open stub must be connected to wires. If you want to connect a source directly to a transmission line, you have to create a wire and connect both the source and transmission line to it. The wire can be very short and, if desired, very far away, to prevent coupling from the antenna. (Remember, the distance between end terminals can be much greater than the length of the "transmission line" connecting them) It might be more convenient, however, to put the extra wire in the general vicinity of the antenna so you can see the transmission line better with the View Antenna display.
Fourth, when a transmission line is connected to the same segment as a source or load, it's important to be aware of the way they're connected together. A transmission line is connected in parallel with a source or other transmission line, and in series with a load, in the same segment.
Connection is sensitive to wire direction. If two vertical elements are defined with one having end 1 grounded and the other end 2 grounded, transmission lines connected to their grounded ends from the same point would result in reversed signals to the two antennas. Imagine each end of a transmission line having two terminals, "1" and "2". A normally connected line will always be connected so that terminal “1” is closest to end 1 and “2” closest to end 2 of each wire, regardless of the physical orientation of the wires. Each transmission line can be reverse connected if desired, which reverses this connection, just like giving a physical line a half twist.
Two examples of phased array antennas using transmission line feed are included as example description files CardTL.ez and 4SqTL.ez.
Transmission lines are defined in the Transmission Lines Window. Placement of transmission line ends is identical to placement of sources. See
for details. There’s no way to connect a transmission line end at a wire junction; the best you can do is to insert a short wire between the wires and place the transmission line end on it. Follow the same procedure and cautions as described at the end of the
A transmission line stub can be created by declaring one end to be open or short circuited. Remember, though, that it’s not capable of radiating, so this stub model can be used only in those situations where a real stub wouldn’t radiate.
be found in the Reference section.
EZNEC User Manual
Using The Transmission Lines Window
EZNEC pro uses NEC transmission line models. There are several very important differences between these and real-life transmission lines, which
and limitations of NEC transmission line models, please acquaint yourself with these differences before using them.
Transmission lines have two ends unless they’re specified to be an open or short circuited stub. Stubs have only one end.
Each transmission line end has to be connected to a wire. To connect a source to a transmission line, you have to create a short wire and place both the transmission line and source on it. Unless you’re modeling a radiating coax line, you can place the wire anywhere in space you want (within reason
– don’t put it 10^6 meters away!) to minimize interaction with the antenna.
Transmission end positions are specified in the same way as source positions. Also, such operations as copying, deleting, moving, and adding are also done the same way as for sources. Please refer to
ones unique to the transmission lines window, are detailed below.
Specifying a stub
A stub is specified by declaring one end to be either open or short circuited.
You can simply enter ‘O’ or ‘S’ in the Wire # column, or you can click the arrow on the right side of the cell and select open or short circuit from the pulldown list.
Transmission line length can be specified in three different ways: physical length, electrical length, and physical distance between ends. If you specify physical length in current length units, the model acts like a line with that physical length. If specified in degrees (electrical length), the line acts like a line of that electrical length. Note: The electrical length of a line specified in degrees doesn’t change with frequency like a real line would. This type of length specification is recommended only for single-frequency analysis.
Any of these three specifications can easily be made by right-clicking the cell in the Length column, choosing the specification type, and entering a value if required. Described below are shortcuts for the three methods.
Physical Length – To specify physical length, simply enter the length in current units, or right-click the Length column. The physical length of the model doesn’t have to bear any relationship to the distance between its ends.
for further explanation.
Electrical Length – Enter the length followed by ‘d’ for ‘degrees’ in the
Actual Distance – Enter ‘a’ in the Length column. This will make the line length the straight-line distance between the ends. This choice isn’t available if one end is shorted or open, that is, the transmission line is a stub.
Specifying Characteristic Impedance (Z0)
In the Z0 column, you can either enter the characteristic impedance in ohms, or you can right-click the cell to open a dialog box with more options. The dialog box lets you choose from a list of common cable types, or enter the wire diameter and spacing of parallel wires. If you use the parallel wire entry,
EZNEC will assume air insulation unless you give a velocity factor. If you enter a velocity factor, EZNEC will infer an effective dielectric constant and
Building The Model calculate the impedance based on this dielectric constant. So the parallel wire entry can be used for ladder line, twinlead, or other dielectric-insulated lines as long as you know the velocity factor. The results of its calculations are shown at the lower left of the dialog box.
Specifying Velocity Factor
To specify velocity factor, enter a positive number no greater than one in the
VF column. Alternatively, you can right-click the cell to open the same dialog box as described above.
Specifying Reverse or Normal Connection
Connection orientation is selected in the Rev/Norm column. Normal connection means that the same conductor of both ends will face the same wire end number. That is, if one line conductor is labeled 1 and the other 2, conductor 1 will connect on both wires toward the wires’ end 1 and conductor
2 toward the wires’ end 2. Specifying a reverse connection reverses the connection to one of the wires, reversing the phase of the voltage and current from the transmission line.
Modeling Coaxial Cable
A lossless non-radiating coaxial cable is electrically identical to a lossless non-radiating two-wire line, so an ordinary transmission line model can be used for modeling a non-radiating coaxial line. A radiating coaxial cable can be modeled quite well with a combination of transmission line model and a wire. The transmission line model represents the inside of the coax, and the wire represents the outside of the shield. The wire is the diameter of the shield, and connected where the shield of the actual cable is. It should follow the same physical path as the real coaxial cable. One of the example files,
DipTL.ez, shows how this is done. (See its
information.) If the coax cable doesn’t radiate, the current on the additional wire will be zero, and the additional wire contributes nothing to the analysis so can be removed.
I don't know of any way to accurately model common-mode effects on a twowire transmission line (that is, how to model a radiating two-wire line). If it's necessary to do this, the line will have to be modeled as two parallel wires.
About Ground Models
Ground has a profound effect on the antenna pattern, and sometimes on its efficiency and feedpoint impedance. EZNEC provides several choices for modeling these effects. The three basic ground types, selected via the Control
Ground Type line, are Free Space, Perfect, and
Real. Free Space is no ground at all. Perfect is a perfectly conducting ground plane which is completely flat, and infinite in extent. The Real ground type is further subdivided into several models, discussed in
ground is also flat and infinite in extent, although one downward step is
EZNEC/4, when using an NEC-4 calculating engine, is able to model
exactly on the ground, but should be at least 1/1000 wavelength above (and
EZNEC User Manual in the case of EZNEC/4, also below) the ground. See
for more information about low horizontal wires.
Free Space – Free space analysis is computationally the fastest. It’s useful for comparing antennas when the end operating environment isn’t known, or for comparing the pattern of a model antenna with published free-space patterns of other antennas. When antennas have similar vertical patterns in the main direction of interest, the gain of the antennas when mounted over ground at the same height will differ by about the same amount as the freespace gain. A dipole and a Yagi of a few elements are in this category, so the free-space gain of a Yagi compared to that of a dipole is very nearly the same as the gain difference when both antennas are mounted at the same height.
This isn’t true, however, for antennas with different polarizations, such as a ground plane and dipole, or for antennas with quite different vertical patterns, such as a dipole and W8JK antenna.
Free space analysis is also useful when working with a line-of-sight antenna having a downward-tilting pattern. When any ground is specified, EZNEC will always report zero signal level at any elevation angle below the horizon. So either free space or near field analysis has to be used to determine how much signal is being directed downward.
Perfect – Perfect ground is useful to simulate the highly conductive ground seen in some antenna test chambers and ranges. It’s can also be used for comparing results with textbook patterns which make the assumption of perfect ground. I’ve often used it to educate people about the effect of finite ground conductivity on antenna patterns by comparing perfect ground results
source placement errors, loss must be reduced to zero. Ground loss can be reduced to zero by temporarily changing the ground type to Perfect.
Wires can be connected directly to perfect ground, and the connections will have zero resistance.
The one thing you shouldn’t use the perfect ground type for is simulating real
Real – The Real ground types are used for simulating actual Earth ground.
Unfortunately, neither of the models is faultless -- otherwise there would be only one Real ground model type instead of two. It’s important to know which to use in a given circumstance, so please carefully study the sections about
Real Ground Types
EZNEC provides two different models for simulating “real” – as opposed to perfect -- ground. Neither does the job perfectly, and one is generally the best for a given situation. It’s important to know which ground model to use and what the limitations of each are.
The two Real ground models are MININEC-type and High Accuracy. The choice is made via the Control Center
Ground characteristics are defined in the
, which is opened by clicking the Ground Descrip line or button in the Control Center. The Real ground models share these common characteristics:
Both are perfectly flat and infinite in extent.
Both are homogeneous to an infinite depth.
Building The Model
Both have user-defined conductivity and relative permittivity
Both allow a maximum of two media, each with its own characteristics. The second medium can be at a lower level than the first if desired.
The ground model consists of one or two media, which are separated by a radial or linear boundary. If the radial boundary is chosen, the first medium is a disk, with the second medium occupying the remainder of the (infinite) ground plane. If the boundary is linear, the first medium occupies the ground to the -x side of a line parallel with the y axis, the remainder of the ground being the second medium. The "boundary" is the radius of the disk (radial type) or the x value of the dividing line (linear type).
When a new Real ground is created, the initial values for its conductivity and
Default Ground Const selection.
EZNEC, EZNEC+, and EZNEC-M are not able to model buried wires.
EZNEC/4 is able to model buried wires only when using the High Accuracy ground model and an NEC-4 calculating engine.
The unique characteristics and uses of each Real ground type are outlined below.
Like the High Accuracy real ground model, the MININEC-type model takes ground conductivity and dielectric constant (relative permittivity) into consideration when it calculates the pattern and gain. However, it considers the ground to be perfect when calculating the impedances and currents. The net effect is that a connection to MININEC-type ground has zero resistance
(unlike the High Accuracy ground model), so there’s no ground conduction loss, but the effect of ground on the pattern is included.
The MININEC-type ground results in faster calculation than High Accuracy ground, and is satisfactory if the antenna doesn't contain any horizontal wires which are lower than about 0.2 wavelength, or higher if the wire is much longer than a half wavelength or so. The MININEC-type ground is preferable when modeling grounded wires, such as verticals. When using MININEC-type ground, a load must be added to grounded wires at the grounded segment to simulate ground system loss.
Do not use this ground type if the model contains horizontal wires lower than about 0.2 wavelength. The minimum height increases for horizontal
wires longer than about a half wavelength.
[EZNEC/4 only]: Standard NEC-4 doesn't have the provision for this type of ground, so it can’t be used with an external NEC-4 calculating engine. The
EZCalc4/4D engine has been modified to include MININEC-type ground.
This ground type can't be used with
Near field analysis is disabled when MININEC-type ground is selected.
Tests have shown that, because of the fundamental way NEC does calculations, near field analysis with MININEC-type ground can produce significantly erroneous results, particularly in the vicinity of a wire which is connected to ground. This is really a contrived situation anyway, because the only way to achieve a ground connection for a real antenna comparable to the MININEC-type ground model is to install a radial system. This will alter
EZNEC User Manual the ground conductivity and local fields, so the MININEC-type ground model isn’t really representative of conditions near a grounded wire in any case.
Use some other ground type for near field analysis.
The High Accuracy (NEC Sommerfeld) ground is required for antennas with low horizontal wires, and is recommended for use unless a direct, zero-ohm connection to ground is required. The minimum permissible height for horizontal wires depends on several factors, but results should be good down to at least 0.005 wavelength, or about 6 inches -- 15 cm -- at 10 MHz., or several wire diameters, whichever is higher. When High Accuracy ground is used, a Sommerfeld-Norton interpolation table is calculated. Although this calculation is quite fast with modern computers, the resulting table is saved on the disk. If future runs require a table with similar values, an alreadycalculated table is read and used instead of repeating the calculations. The key parameter which determines whether an existing table is close enough is the ground's complex permittivity (which is a function of the frequency and the ground conductivity and permittivity). If a table is found for a magnitude within a user-specified tolerance of the required magnitude, it will be used. You can change this tolerance, if desired, from the Control Center Options menu. A tolerance value of a percent or so is adequate where horizontal wires aren't extremely close to the ground. In situations requiring high accuracy, or where there are low horizontal wires, a much smaller tolerance, perhaps 0.05%, is recommended.
Direct connection of wires to High Accuracy type ground shouldn’t be made.
The High Accuracy ground type should be used any time the model contains low horizontal wires, and is required for modeling buried wires with EZNEC/4.
Limitations of Real Ground Models
EZNEC's Real ground model might not be representative of some real ground situations. At lower frequencies, current penetration becomes deep, with skin depth being on the order of several meters at the lower end of the HF range.
Real ground is likely to be stratified, with widely varying conductivity and dielectric constant within this depth range. Because NEC, therefore EZNEC, assumes a perfectly homogeneous ground of infinite depth, the model may not accurately reflect the antenna's actual environment. While NEC is believed to be accurate in its evaluation of the model, it cannot accurately predict antenna performance if the model does not adequately represent the real situation. Consequently, EZNEC results for antennas with very low
frequencies, may be of limited usefulness in predicting actual antenna system performance. EZNEC is not able to model ground as being composed of other than a single homogeneous material of infinite depth. EZNEC, EZNEC+, and
EZNEC-M are not able to model buried wires.
Another factor limiting the ability to predict antenna performance when ground is a major factor is that actual ground conductivity appears to vary with frequency, an effect not modeled by EZNEC. Consequently, conductivity values for frequencies other than the frequency of use might not be accurate.
Building The Model
It’s also important to be aware of your limited ability to make realistic
for more about the limitations of
Real ground models.
[EZNEC/4 only]: The Real, High-accuracy (Sommerfeld) ground model will produce erroneous results if the ground conductivity is specified to be much greater than that of salt water (about 5 S/m) and an NEC-4 calculating engine is being used. This is a limitation of NEC-4. NEC-2 is more tolerant of high conductivities.
Using The Media Window
This window is available when Real ground type is selected, and is opened by clicking on the Ground Descrip line or selection button in the Control Center.
The ground constants entered in this menu are used somewhat differently for two purposes. When Real/High Accuracy ground is chosen, the constants of the first medium are used during determination of antenna impedance and currents. The constants of both media are used during pattern calculation, by modifying the strength and phase of the field reflected from the ground.
(Exception: Only the first medium is used when ground wave (EZNEC pro only) or near field analysis is being done.) Ground constants are not used if
Free Space or Perfect ground is specified, and are used only for pattern calculation if Real/MININEC-type ground is being used. Real/MININEC-type analysis assumes a perfect ground during impedance and current
for more information.
Selecting the Conductivity and Dielectric Constant
The conductivity in Siemens/meter and the dielectric constant (relative permittivity) can be entered directly in the corresponding columns if desired.
Right-clicking either of these columns opens a dialog box giving you a choice of a wide variety of typical ground types. The selection of ground conductivity makes little difference for horizontal wires of moderate height, but it can be very important for vertically polarized antennas. When a medium is first created, its initial conductivity and dielectric constant values are determined
selection Default Ground Const.
Adding A Second Medium
To add a second medium, click Add in the Medium menu, or simply enter the values in the add row at the bottom of the grid. Empty cells or newly created media will use the conductivity and dielectric constant values specified by the
Completing the Specification
Enter the second medium height and boundary in the remaining two columns.
These values are fixed and can’t be altered for the first medium. To change the boundary type between the media, select Boundary Type in the Medium menu.
Adding an NEC Radial Model
Using Two Ground Media
The ground may be broken into two "media", each having its own conductivity and dielectric constant (relative permittivity). The second medium can be at a
EZNEC User Manual different height, but must be at the same level or below the first medium. The media can be arranged in parallel slices or concentric rings. One use of two media would be to model an antenna on a lake surrounded by land. A very important thing to understand is that the second medium is used only for far field pattern calculations, and is ignored for all other purposes. Be careful when using two media, and keep the following in mind:
1. Even if you place the antenna over the second medium, EZNEC will always use the ground constants and height (z = 0) of the first medium for calculation of the impedances and currents.
2. The second medium is used only for far field calculations. Near Field and Ground Wave calculations assume that the first medium is of infinite extent, and ignores the second medium.
3. The effect of the second medium is taken into account only in a very simplified way. The vertical pattern is generated by tracing “rays” direct from the antenna and reflected from the ground. When a second medium is used, the ground reflection “ray” is determined by whichever medium it strikes the top of. The “ray” does not penetrate either medium, and diffraction or similar effects aren’t considered. Because of
this, a highly conductive inner medium and normally conductive outer medium is not a good model of a ground radial system, and shouldn’t
be used for this purpose.
4. Buried wires in EZNEC/4 will always be treated as though they’re immersed wholly in the first medium.
When a second ground medium is first created, its conductivity and dielectric constant are set to the default values determined by the
Default Ground Const selection.
Connecting Wires to Ground
A Wire end is connected to ground by specifying a zero z-coordinate.
EZNEC pro considers a wire end to be connected to ground if it is within
1/1000 of a segment length of ground. A good general practice is to space unconnected vertical or sloping wires at least several wire diameters above ground.
If you connect a wire to ground when using the High Accuracy real ground type, the program makes the connection with an unpredictable series resistance. EZNEC will warn you when this situation occurs. Use the
MININEC-type ground when modeling antennas with vertical, grounded wires if the ground system itself isn't part of the model. Note that the MININEC ground model isn't available when using an external (user-supplied) NEC-4 calculating engine with EZNEC/4.
Sometimes it’s necessary to both make a ground connection and use High
Connecting to High Accuracy Ground
Sometimes it’s necessary to make a ground connection and use High
Accuracy ground. An example of this situation is in modeling a Beverage antenna, where a connection is needed for the termination resistor. Another example is an inverted L antenna where the horizontal portion is lower than about 0.2 wavelength. In these situations, the best approach is to approximate
Building The Model a buried radial system by creating horizontal radials just above the ground, and make the “ground” connection to the radials. [EZNEC/4 only: The best approach for this program is to directly model the actual (usually buried) ground system and make the “ground” connection to it, and disregard the remainder of this topic.] A height of between about 1/100 and 1/1000 of a wavelength is suitable, but in any case no less than several wire diameters. If a low impedance connection is required, make the radials about a quarter wavelength or odd multiples long, and avoid lengths approaching a half wavelength or multiples. These aren’t free space wavelengths, however, but wavelengths for a wire at the radial height. A half wavelength for a wire very close to the ground will be less than in free space, though. You can determine the wavelength by modeling a dipole at the height of the radials and adjusting its length until it’s resonant. Be sure you’re seeing the lowest (series) resonance, which for very low wires will occur with a dipole length somewhat less than a free space half wavelength. The best radial length will be about half the resonant dipole length.
Radials can be easily constructed using EZNEC’s
. Above ground radials will show resonant effects more sharply than buried radials, but will provide a reasonable approximation of a buried radial system.
The NEC Radial Model
If you would like to use the NEC buried ground radial model, please first read this section very carefully. It deals only with the NEC ground radial model available in the Media Window (Other menu), not the "Create Radials" feature in the Wires Window, or radials modeled as wires.
The NEC buried ground radial model is similar to the model used in ELNEC and MININEC. It is not actually a model of buried wires, and it does not
model the effect of ground radials on antenna impedance, current, loss,
or efficiency. It does approximately model the effect of ground radials on the pattern, an effect which is generally slight, unless ground radials are very
for more information.)
The effect of the NEC buried ground radial model on feedpoint impedance is different than the effect of a real radial system on a real antenna. The presence of any NEC radials at all, even one very short radial, will change the
NEC-calculated ground connection resistance to zero, but only at the point (x, y, z) = (0, 0, 0). Experiments have shown this to not always be true when using the NEC-2 engine and wires connecting to ground at a sloping angle.
The resistance of connections to ground at other points will have an unpredictable resistance, as they do without the radials. This means that the
model radials won't accurately predict the input impedance of a
grounded wire such as a vertical antenna. The NEC buried ground radial model is used only for calculation of ground reflection coefficients for the far field patterns. Even for this limited use, the buried radial model isn't accurate unless there are many radials and the radial field. Accuracy is also poor when the radial field diameter is only a fraction of a wavelength and/or the antenna is relatively close to the radial field. For typical vertical antenna radial fields, a model with radial wires suspended just above the ground (or below the ground with EZNEC/4) results in much greater accuracy than using the NEC radial model. The conductivity of the radials is "peanut-buttered" over the
EZNEC User Manual entire ground area that the radials cover (varying with distance from the origin), and the result is simply paralleled with the ground conductivity in the region where the radials are placed. Four radials simply look like thinner
"peanut butter" than 120 do.
Once again, the NEC model radials do not represent a true picture of the
effect of real ground radials. Other methods are generally preferred, as outlined in
. Ground radials can be modeled with reasonable accuracy using EZNEC/4 with an NEC-4 calculating engine, so the use of the radial model isn't generally recommended if this option is available.
Before it can be used with the standard or EZNEC+ program types, the NEC buried radial model feature must be enabled by means of an addition to the
EZNEC.INI file. To make this modification, open the Control Center Utility menu and select Edit .INI File. In the [Special Options] section, add the following line:
NECRadials = On
Save the file and close it, then end EZNEC. Wait a few seconds for the disk cache to dump, then restart EZNEC. NEC radials (and the Other menu selection in the Media Window) will now be enabled. This addition to the
EZNEC.INI file isn’t required with EZNEC pro.
Once this feature is enabled, radials can be entered and modified via the
Other menu in the
out) unless all the following conditions are met:
1. Except for EZNEC pro, the feature must be enabled with the added
EZNEC.INI line described above.
must be Real, MININEC-type.
3. There must be two media.
4. The media boundary type must be radial, not linear. (When the boundary is radial, the upper heading of the rightmost Media Window column is “R Coordinate”, not “X Coordinate”. You can change it via the
When all these conditions are met, the choice will be available, and you can select the number and diameter of the radials. The radial length is always the diameter of the first medium, so to change the length you change the boundary of the second medium.
If desired, you can enter the wire diameter as wire gauge (AWG) by typing '#--
' where "--" represents the wire gauge. Gauges of wires larger than #0 (i.e.,
#00) are not permitted.
After the entry is complete and the dialog box closed, the number of radials will appear in the Control Center Information Window as part of the Ground
Interpreting The Results
feature or seen in tabular form by clicking the Control Center Currents action button. The currents give important information about antenna operation. In addition, they're invaluable in assessing whether the antenna is working as intended and in spotting conditions where EZNEC is being used beyond its capabilities. Note that the View Antenna display is intended as a visual aid.
Although the overall display is correct, it has been smoothed so that details about the current along a single segment or at the junction of two segments may not be precise. If you need this level of detail, refer to the tabular data.
One thing to look for is symmetry. If the antenna is symmetrical, the currents should be also. If not, some error has been made in wire definition, source placement, or some other area. For example, the current from the vertical part of a ground plane antenna should split evenly among the radials if the radials are the same length and evenly spaced. Make it a habit to look for these symmetries and you'll spot problems before bad results lead you astray.
Another thing to look for is abrupt and unexplained current changes (instead of a smooth change from one segment to the next). This usually is due to not having enough segments but might be due to some other factor causing
EZNEC to be operating beyond its limits. Sudden current reversals may be no cause for concern as they might be due to the way the wires have been defined. Positive current flow always is defined as being from end 1 to end 2, so if two end 1's or two end 2's are connected together, a 180-degree shift in current direction will be indicated at the junction of the wires (provided View
Antenna phase information is on or you’re looking at the currents in tabular form). The current actually is continuous as it should be, but the definition of direction changes from one wire to the other. There's nothing wrong with connecting wires in this fashion but don't be confused by the currents EZNEC shows as a result. Watch for this also when using multiple sources -- see
Current phase information can be included on the View Antenna display, but it frequently conceals important information about what's happening to the
for more information about this feature.
The importance of currents is underscored by the fact that the field generated by a wire is proportional to the current flowing on it. If one element of a multielement antenna shows a small current relative to the others, it's not contributing much to the overall field. It might, however, be generating just enough to deepen a null in the pattern. If your model contains several nearby wires, towers, and other objects, a look at the currents on them will quickly tell you whether they're having a significant effect on your antenna's performance.
If the current on an object is small relative to the current on your antenna, you generally can remove it from the model without much impact on the result
(unless deep nulls are important; even small fields can have a significant effect on nulls). Shorter conductors require more current than long ones to have the same effect.
EZNEC User Manual
Load data are shown by clicking the Load Dat action button in the Control
Center. The voltage across, current through, impedance of, and power loss of each load is shown. In addition, the total load loss is shown in watts and dB.
The loss figures are invaluable in determining the loss caused by traps, loading coils, and the like. You can also determine the voltage across the load or current through it under actual operating conditions by entering, via the
Power Level selection in the Control Center Options menu, the power to the antenna.
If two identical loads appear on identical adjacent segments, EZNEC will also show you the data for the two loads together. This is so you can simulate a load placed at a wire junction by splitting it in half and putting it on adjacent
The impedance, SWR, voltage, and current at each source can be viewed or printed by clicking the Src Dat action button in the Control Center. In addition, a graph of the SWR vs. frequency can be displayed by clicking the SWR action button. If EZNEC reports a very low value of resistance at any source, be careful -- this might indicate operation beyond EZNEC's limits. If two elements are closely spaced and fed out of phase (W8JK-type antennas), the low resistance is real but the real antenna might not work like EZNEC predicts unless you’ve included wire loss (a Control Center choice). Losses become important when the resistance is low, so be sure wire loss is included if a low resistance is indicated. Negative resistances sometimes are reported for multi-element arrays. These actually can occur but are subject to the same cautions as low positive resistances. (The SWR for these sources will be reported as "undefined", and shown on the graph as infinite.) A negative source resistance where only one source is used is positive indication of operation of EZNEC beyond its capabilities. Very small loops will cause this condition, as will overlapping wires or wires occupying the same space. The latter condition should be caught by NEC-4's geometry test (EZNEC/4 only), but won't be caught with EZNEC or EZNEC-M.
The SWR shown is the SWR which would be present on a feedline connected in place of the source. Values are given for 50 ohm and user-specified feedline impedances. (The user-specified impedance is selected with choice
Alt SWR Z0 the Control Center Information Window.) The SWR is directly calculated from the source impedance. If a source is connected to a transmission line model and you want to know the SWR on the transmission line, the SWR reference impedance must match the characteristic impedance of the transmission line.
Negative Input Resistance
Occasionally a negative resistance might be shown at one or more sources. If a single source is being used, this is a positive indication of a numerical error, since it represents an antenna which is producing, rather than accepting power. The most common cause is a source placed in a very small loop. (See
such as overlapping, overlying, or crossing wires. When multiple sources are used, a negative input resistance can be a valid result. This actually occurs in
Interpreting The Results some arrays, and represents an element which is delivering power back to the feed system. It gets this power from the other elements via mutual coupling.
The 4Square example description illustrates this characteristic. There’s more information in the Antenna Notes file for this example.
Far Field Table
The Far Field Table is accessed by clicking the FF Tab action button in the
Control Center. It shows the field strength at each azimuth and/or elevation angle. If you’ve selected a 3D plot type, you’ll be asked which data to display and how it’s to be organized.
The Far Field Table data can be shown in several different formats, as selected via the Control Center Options menu Far Field Table Units selection.
dBi or dBref – Shows the same data as the 2D plot. Values are relative to the reference value set by the Control Center Ref Level choice, or in dBi if the reference level is zero.
mV/m for 1 kW at 1 mile – Gives the field strength in mV/m at one mile, assuming a supplied power of 1 kW. Any setting of the Control Center
Options/Power Level is ignored.
mV/m for 1 kW at 1 km – Same as above, but at a distance of 1 km.
EZNEC pro only: Ground wave analysis choices
dBi or dBref – Same as for ordinary far field.
mV/m – Absolute value of the field at the distance and height specified in the
Control Center Information Window. You’ll generally want to set the power level, via the Control Center Options menu Power Level selection, before using this option.
Reference section for more details.
In EZNEC+ and the EZNEC pro programs, you can also choose whether to show linear or circular components. This is done with the Control Center Desc
Options selection, Plot/Fields tabs.
Near Field Table
Unlike far fields, the near fields can be pointed in any direction. They are broken into three components, in the X, Y, and Z directions. A total is also shown. The total is generally all that will be used unless you have an interest in the orientation of the E or H field. EZNEC also reports, near the top of the list, the largest field that was found. Be careful that none of the steps falls inside a wire; if it does, the results for that step won't be meaningful, and it could be reported as the maximum value. Near field analysis uses only the first ground medium. If two ground media are defined, the second will be ignored.
Because the ratio of E (electric) to H (magnetic) near field depends on the antenna type and the distance from it, the two fields must be analyzed separately.
Note that "Near Field" analysis actually reports the total field, so it's valid at any distance, including far from the antenna. It can also be used in the standard EZNEC program for evaluating the ground wave. For more
in the Reference section.
EZNEC User Manual
Remember that many factors affect the results from a modeling program.
EZNEC should not, under any circumstances, be used to determine whether the energy or field strength from an antenna presents a hazard
or unsafe condition. This applies to all results, including both Far Field and
Far Field Patterns
Three choices of far field plot are available, (2D) Azimuth, (2D) Elevation, and
Three Dimensional (3D), although only azimuth is available if the ground wave component is included (EZNEC pro only). Any elevation angle can be chosen for azimuth plots, and any azimuth angle for elevation plots. 2D plot range can be restricted if desired. Both the observation distance and height above ground can be freely chosen when the ground wave component is included
(EZNEC pro only). EZNEC includes a visualization aid for orienting the pattern relative to the antenna, in the View Antenna display, where the 2D pattern plot or a "slice" of the 3D plot can be superimposed on the representation of the antenna. More information about these features can be found in
sections of the Reference chapter.
Because the far field sky wave from a horizontally polarized source is zero at a zero elevation angle for any ground type, and a vertically polarized source produces zero sky wave for any finite-conductivity ground, attempts to calculate a 2D pattern without the ground wave component under these conditions will result in an error message.
The 2D Data box (activated via the 2D Display View/Show Data selection) shows a summary of key pattern characteristics, such as beamwidth and front/back ratio.
EZNEC offers an alternate azimuth coordinate choice, "compass bearing".
This presents azimuth angles in degrees clockwise from the +y axis (straight up on the 2D plot), to correspond to compass bearing. The choice is made in the Control Center Options menu as Angle Convention. No change to any plot orientation occurs when changing between standard and bearing representations; only reported angles change.
Various options for far field display can be selected in the Control Center window and the Control Center Desc Options selection.
Antenna Notes are a way to include notes with your antenna description. An
Antenna Notes file is an ordinary ASCII text file which has the same name as the associated antenna description file, but with a .txt extension in place of the description file .ez extension. The Antenna Notes file is kept in the same directory as the description files. Antenna Notes files can be edited with any text editor, or from within EZNEC.
To create, view, or edit an Antenna Notes file for the current description, select Edit Current Antenna Notes from the Control Center File menu. This
. When you’re finished, select File/Save within the Editor, then close it.
When you save an antenna description, you might see a dialog box asking you what to do with the corresponding Antenna Notes file. Both the Antenna
Notes file associated with the current description, and the one associated with the saved file name are shown, to help you decide. This dialog box won’t appear if the text in the two files is identical or if you’re saving the file with the same name as when it was opened.
EZNEC pro only: You can also use Antenna Notes with NEC format files.
Operation is similar to operation with .ez files, except that you’ll see a temporary file name when you open the EZNEC Editor. With NEC format files,
Antenna Notes are saved as a series of CM (comment) “cards”. When you open the Antenna Notes for editing, EZNEC copies the CM card comments to a text file and opens that instead. Because there is no separate permanent
Antenna Notes file, changes you make aren’t permanent until they’re written
into the NEC format file. This isn’t done until you save the description. So be sure to save the description file after you edit the Antenna Notes.
Automatic wire segmentation is available in the Wires Window (Wire/Auto
Seg) and in the
display (Segmentation menu, enabled only if one or more wires produces a warning). Two choices are offered,
Conservative and Minimum Recommended. The Conservative choice is best for general use. If computation time becomes too long or the total number of segments becomes excessive, the Minimum Recommended choice can be used. In any case, don’t blindly depend on the automatic segmentation to always choose the optimum number of segments. There are many occasions, such as several described in the chapter “Some Special Cases” in “Modeling
The Antenna Structure” which require more segments. In some other cases, such as placement of a source or load on a short wire or when dealing with closely spaced parallel wires, the segment length or alignment is important.
Automatic segmentation won’t recognize these special circumstances, so it will be up to you to determine how many segments are required.
Probably the best use of automatic segmentation is as a first segmentation of a new antenna description, as an initial setting.
EZNEC User Manual
Segmentation Check has a related feature called Fix Segs which is described
Average Gain is a valuable tool in detecting situations where EZNEC’s calculating engine is having difficulty, particularly in situations involving source placement. A second use for Average Gain is to evaluate the amount of loss incurred by wire resistance or the reaction of the field with a finitelyconducting (“Real”) ground.
The Average gain is the total power in the far field (determined by integrating the far field in all directions) divided by the power delivered to the antenna by the sources. It’s shown at the bottom of the Control Center after a 3D far field plot has been run. It is not computed for Azimuth or Elevation plot types.
EZNEC’s NEC calculating engine is very particular about the length of segments containing sources, and nearby segments. When placement isn’t to its liking, an error in the form of inaccurate gain and impedance will frequently occur. Without an independent means of evaluating gain, this error can go undetected. A solution to the problem is to calculate the Average Gain.
Average Gain is meaningful for assessing the validity of results only when no loss mechanisms (wire loss, resistive loads, or “real” ground) are present in the model. When the Average Gain is one (with no loss present), the program is producing correct results. If it deviates significantly from this value, results are in error, and source placement should be altered if possible. Every effort should be made to correct the problem. But if this isn’t possible, the pattern and gain figures can be corrected by dividing them by the Average Gain (or by subtracting the Average Gain in dB from them). The procedure for using
To use Average Gain to assess wire or ground loss, you should first confirm that the Average Gain is near unity when all loss has been removed from the model. When lossy factors have been restored, the Average Gain indicates the loss incurred by these factors.
If it’s not possible to reduce the Average Gain to nearly unity (zero dB), the gain can be corrected with fair accuracy by subtracting the Average Gain in dB from the reported field strength in dBi. For example, if the reported gain is
2 dBi and the Average Gain is 3 dB, the actual gain is 2 - 3 = -1 dBi. If there is only one source, the feedpoint resistance can also be corrected by multiplying the reported feedpoint resistance by the plain numerical (not dB) Average
Gain. Unfortunately, the reactance error isn’t predictable so can’t be corrected by this method, and the feedpoint resistance correction won’t work if there are multiple sources.
Combining Antenna Descriptions
Antenna descriptions can be combined into a single model. One typical use would be to separately analyze Yagi antennas for different bands, then combine them to study interactions. Or parasitic structures might be modeled separately then combined in various combinations in a single model. To add an existing antenna description to the current model, choose Add Description from the Control Center File menu. Note: Saved descriptions must always contain at least one source. So if you want to save a model of a parasitic
Reference structure (that is, one which doesn’t have a source), you have to add a source to it. This source can be deleted after combining it with an existing description which does have a source.
Combining and importing are sometimes confused. If you want to add wires whose coordinates are in an ASCII file, or want to replace your current model
The EZNEC Editor is basically a copy of the Windows Notepad application.
It’s used as a convenient way to edit text files from within EZNEC. Controls, menus, and operation are very similar to Notepad, although occasionally you’ll see a difference. The EZNEC editor is automatically opened to display a number of EZNEC files and outputs.
A few words about fonts -- When used for displaying tabular outputs like
Currents, Source Data, Far Field Table, and so forth, the EZNEC Editor restricts your choices to fixed-width fonts such as FixedSys and Courier New.
This permits the columnar data in these files to be properly aligned. Some fonts, such as FixedSys, are screen fonts only and can’t be printed. If this happens, either Windows or EZNEC will substitute another font during printing. If Windows substitutes a variable-width printer font for a fixed-width screen font, the columns in certain outputs won’t line up properly. If this happens, select a printable fixed-width font. The Editor will remember the last fixed width font you chose, and will continue to use it in the future until you change it again.
You can use the EZNEC Editor to view or edit any file, not just EZNEC files, by selecting View File or Edit File from the Control Center File menu. The only difference between these two is that if you open a file with the View File selection, you won’t be allowed to save it under the same name. That is, it protects the original file from being changed by the editing process.
EZNEC's frequency sweep capability can be a very valuable tool in evaluating antenna performance over a range of frequencies. However, operation is somewhat different in the frequency sweep mode, so it's important to understand the operation in order to get the most from this feature. Note that the frequency "sweep" is actually discrete steps. These can be evenly spaced or, if read from a file, any frequencies in any order.
In non-frequency sweep operation, EZNEC calculates antenna impedances, currents, and pattern, and keeps the current and pattern information. When changes are made to the antenna, only necessary recalculations are done.
For example, when the plot elevation angle is changed, only the pattern is recalculated. This is not the case with frequency sweep. It's not practical to keep all the information for all frequencies, so final calculation results are written into an ASCII file after each frequency step. Data present in arrays are erased and EZNEC is reset before beginning calculations at the next frequency. Therefore, calculation results from a frequency sweep are available only in the form of the file containing the data and, optionally, a trace for each frequency. The exception to this is that data from the last frequency in the sequence can be viewed.
EZNEC User Manual
Two or three outputs are available from the frequency sweep: MicroSmith or winSMITH files and data output are always available for selection; 2D far-field plots (traces) are available only when far-field analysis (EZNEC-M and
EZNEC/4: with or without ground wave) is chosen for frequency sweep. You can choose to have EZNEC save any combination of these. Additional impedance and SWR data are always saved, in a separate file, regardless of the outputs you choose to keep. These data are used for the SWR Graph, and reside in a comma-delimited ASCII file named
program directory. This file remains after the program ends and may be used for other purposes as desired. Note: MicroSmith and winSMITH limit the number of frequency steps they will accept. See MicroSmith or winSMITH for more information.
Following is a detailed description of the features in the Frequency Sweep
Setup dialog, which is opened via the Control Center Setups menu,
Frequency Sweep selection.
Frequency Sweep Off/On
Turns frequency sweep off and on.
Selects frequencies to be used for the sweep. Frequencies can be specified in one of two ways. If specified as start, stop, and step frequencies, the frequency steps will be evenly spaced, extending from the start frequency to the stop frequency. If a frequency sweep input file is specified, frequencies are read in order from the file, and there are no restrictions on spacing or order.
Start, Stop, and Step Frequency (MHz) – Specifies the range of frequencies to sweep, and the step size.
Read Frequencies From File – If this is checked, Start, Stop, and Step
Frequency entries will be disabled, and a file name is required. The file must contain a list of frequencies to be used in the sweep. See
unchecked, File Name, Select, and Edit File are disabled.
File Name – Shows the name of the input file you’ve chosen, if Read
Frequencies From File is checked. You can not enter a file name in the text box; the file must be chosen by using the dialog box opened with
Select – Opens a dialog box to allow you to choose an input file.
Edit File – Opens the file shown in the File Name box for editing in the
allowing you to choose one.
Field To Calculate – Selects whether EZNEC will run a far field or near field analysis for the frequency sweep. If Near Field is chosen, pattern plot output and pattern analysis data are not available, and field strength table data will be near field.
Output – Selects what data will be calculated and saved during the frequency sweep. There are three general categories of output, listed below. For each category, the output file name is specified by clicking the Select button, and the choice is shown in the corresponding text window.
Pattern Plots – If this is checked, 2D pattern plots will be saved, and shown when the frequency sweep is completed. This selection is disabled if Near Field is chosen as the Field To Calculate. Select this option when you want to see or save 2D plots for all the sweep frequencies. These plot (trace) files aren’t automatically erased when the sweep ends, so they can be treated later like any other trace files.
It’s recommended that you use a name like “temp” for files you won’t want to view at a later date, and use this same name each time you want to see frequency sweep plots but don’t need to keep them. The extension .P# is added to the file name you specify, with # being 1 for the first frequency, 2 for the second, etc. These are EZNEC OpenPF binary plot files, and are not readable without specialized software. To save far-field plot data in readable, ASCII form, check Data File and
Field Strength Table.
MicroSmith or winSMITH Files – If this choice is selected, MicroSmith or winSMITH input files will be saved in the directory specified in
Control Center Options menu, Folders/MicroSmith or winSMITH Files selection. The choice of program is made with the Control Center
Options menu, Smith Chart Program selection. Extensions expected by the Smith Chart program will be added by EZNEC to the specified name. Note: winSMITH v. 2.00 allows no more than 15 frequency steps, so EZNEC won’t write more than this number into a winSMITH file. MicroSmith v. 2.000B and earlier permit no more than 8 frequency steps in a .DAT file (for frequency dependent loads), while later versions allow 100. EZNEC can be set to limit the number of
MicroSmith .DAT file steps to either 8 or 100. See the MaxMSFreqs option in
for information about how to set this limit.
Data File – Saves selected data in ASCII format in a text file. The choices of data which can be saved, in the dialog Data File Contents section, are listed below.
Field Strength Table – Saves a table of field strength values for each frequency, either far field or near field, as determined by the Field To Calculate choice. The format of the data is the
field strength is calculated are defined in the Near Field Setup dialog.
Source Data (Incl. SWR) – Saves source data (impedance, voltage, current, power, and SWR), in the same format as for the single frequency
(Src Dat) display.
Load Data – Saves load data (impedance, voltage, current, and power) in the same format as for the single frequency
(Load Dat) display.
Currents – Saves wire currents in the same format as for the
Pattern Analysis – Saves information about the plot such as maximum value, angle at which the maximum occurs, front/back or front/side ratio, etc., essentially the same information that is presented in the
. This choice is disabled when Near Field is selected as the Field To Calculate.
EZNEC User Manual
Although any extension can be specified for the file name by first choosing “All files” in the “Files of type” window of the file name selection dialog box, it’s recommended that you let EZNEC add a “.txt” extension by leaving “Text files” as the “Files of type” choice. This cues
Windows to the fact that the result is a plain ASCII text file.
This powerful feature, which runs automatically before each calculation, checks the model for errors such as wires crossing at other than a wire end or segment junction, wires occupying the same space or overlapping, or wires coming too close to each other.
Calculation isn't allowed to proceed if geometry errors are found. Wire crossings and connection at segment junctions are permitted by NEC, and although not generally recommended for EZNEC operation (due to disconnection occurring when segmentation is changed), no errors will occur if wires cross at a segment junction. However, NEC files created by external programs and imported into EZNEC pro often contain segment junction connections. By default, the Geometry Check will show a warning if wires cross at segment junctions. If you commonly use files originally intended for
NEC use which contain wires crossing at segment junctions, you can suppress these messages via the EZNEC Geometry Check selection in the
Control Center Options menu. There's also an option in the new Desc Options dialog (opened by clicking Desc Options in the white pane of the main window), General tab, to allow calculations to proceed if the only errors found are that a segment center is within another wire (see below). This choice is saved with the description, since the condition sometimes causes serious calculation errors and sometimes not, but it’s sometimes hard to avoid. The selection affects both the EZNEC Geometry Check and, in EZNEC/4,
SEGCHK if enabled.
For users familiar with NEC-4, the Geometry Check tests for the same kinds of errors as NEC-4’s SEGCHK. However, it’s faster and a bit more conservative than SEGCHK, and it catches some geometry errors which
SEGCHK doesn’t. And it’s present in all EZNEC program types, and runs regardless of the calculating engine chosen. EZNEC/4 users have a Pre-Calc
Geometry Check selection in the Control Center Options menu, to choose between the EZNEC and NEC-4 checks, or both, when running an NEC-4 calculating engine. I suggest keeping the EZNEC Geometry Check enabled, unless you have some special need to use the NEC-4 check. If you ever do see an error which SEGCHK catches that EZNEC’s Geometry Check doesn’t,
I’d like very much to hear about it.
"Center of wire x end segment within wire y" is a message which brings frequent requests for explanation, so a detailed description of its cause has been included here. It occurs when two wires are connected at an angle.
Suppose, for example, that one wire (let's call it wire y) has a diameter of two inches, and another wire (wire x) is connected to it at a right angle, as shown in the diagram below. If the segments of wire x are shorter than two inches, the center of the end segment of wire x will be inside wire y. The message will appear with longer wire x segments and/or smaller wire y diameter if the angle between the wires is acute. Sometimes this condition causes serious computation errors, and sometimes not. If possible, it should be avoided by
Reference decreasing the diameter of wire y, lengthening the segments of wire x, or both. The Geometry Check report of this condition can be overridden for the current model, allowing calculation to proceed, via the Desc Options selection,
override. An Average Gain check should be run, although a good value isn't a guarantee that results will be valid.
Ground Wave Analysis
This feature is available only in the EZNEC pro programs EZNEC-M and
Ground wave analysis is similar to far field analysis in that it uses approximations valid only in the far field, but differs in that it includes the ground wave, and reports the absolute field at a specified distance rather than a relative one at an arbitrary distance.
Ground wave analysis is enabled via the Gnd Wave Dist (ground wave distance) Control Center selection. When Ground Wave analysis is enabled, the Elevation Angle or Azimuth Angle selection changes to Observation
Height, which you can also specify. Note that if an observation height greater than zero is chosen, the ground wave distance is the horizontal distance from the origin to the observation point, i.e., the projection of the actual distance on the XY plane. The actual distance from the origin to the observation point is the square root of the sum of the squares of the ground wave distance and the observation height. If ground wave analysis is enabled, Plot Type is
EZNEC User Manual restricted to Azimuth. Results can be presented as a dBi plot, or in a table of dBi or absolute electric field values, the choice being selected with the Control
Center Options menu Far Field Table Units selection. Ground wave analysis may be done with any ground type except free space. Note: If more than one medium is defined with Real ground, the analysis will be done using only the constants of the first medium as though it extends to infinity; the second medium, if present, will be ignored.
Modifying A Group of Wires, Sources, Loads, or Transmission Lines
The Group Modify feature is common to all the Input Grid Windows except the
Media Window. It’s a powerful feature for modifying a number of items at once. Many of the normal editing features and shortcuts apply when Group
Modify is activated.
Group Modify is activated by selecting Group Modify from the Wire, Source,
Load, or Transmission Line menu and specifying the range of item numbers to be modified. Alternatively, the items can be selected before making the menu selection. While Group Modify is active, the selection is frozen, and items can’t be added to or removed from the selected group. Any changes made to any of the items is applied to all items in the selected group. Most changes which can be done on individual items, including shortcuts, can be done on a group of items using Group Modify.
To turn Group Modify off, select Wire, Source, Load, or Transmission
Line/Group Modify again.
Near Field Analysis
As of this writing, EZNEC and similar programs are accepted by the FCC and some counterpart bodies in other countries as permissible for calculating compliance with RF exposure requirements. However, EZNEC results
should never be used in any judgements regarding human safety. Please
for further information.
Near field analysis, as it applies to EZNEC, is something of a misnomer, because the complete field is actually calculated and reported. So near field analysis results apply equally well in the far field.
EZNEC presents near field data only in tabular, not graphical, form.
Near field analysis is run by clicking the NF Tab button in the Control Center.
(Note: This feature is disabled when MININEC-type ground is selected. For more information, see “MININEC-type” in the
points in space where EZNEC will calculate the field strength are specified in the Near Field Setup dialog, chosen in the Control Center Setups menu, Near
Field selection. The entries in the dialog are described below.
Start, Stop, Step Columns – These are the locations in space, relative to the origin, where EZNEC will calculate the field strength values. EZNEC begins at the Start location, and steps by increments in the Step column until the Stop location is reached.
X, Y, and Z or Dist, Zen Ang, and Az Ang rows – The titles of the rows depend on the Coordinate System selection. For Cartesian coordinates, the rows represent the x, y, and z distances from the origin in current units. For spherical coordinates, they represent the radial distance from the origin in
Reference current units, the zenith angle (angle downward from the z axis) in degrees, and the azimuth angle (angle counterclockwise from the x axis) in degrees.
Field – Either the E (electric) or H (magnetic) field can be calculated. As distance from the antenna increases, the ratio E/H approaches 120 pi, so at sufficient distances, calculation of only one field is adequate because the other is then known. This isn’t true, however, when close to the antenna.
Coordinate System -- Stepping can be done either in Cartesian (x, y, z) or spherical coordinates, but results are always shown in Cartesian coordinates.
See X, Y, and Z or Dist, Zen Ang, and Az Ang rows, above, for explanations of the spherical coordinates.
Total Steps – This shows the total number of locations at which the field will be calculated. You can update this window by pressing <Enter> when the cursor is in any of the position entry boxes.
An antenna can easily be rescaled by clicking the Frequency line or button in the Control Center Information Window, then checking the Rescale box. The items which will be rescaled are wire end coordinates, wire diameter if not specified as wire gauge, wire insulation diameter, second medium height, second medium boundary, ground wave distance and observation height
(EZNEC pro only), and transmission line lengths if not specified in degrees.
(Transmission line Z0 isn't modified even if it was initially entered as wire diameter and spacing.)
The above items will be modified even if Wavelengths is the chosen unit of measure.
Note that results might not be exactly the same after rescaling, for several reasons. One is that not all items are rescaled. For example, if you defined some wire diameters as wire gauge, they won’t be scaled, so the final antenna won’t have exactly the same proportionality as the original. Another factor is ground and wire conductivity. Neither of these is scaled, yet the resistance of both changes with frequency as a consequence of the difference in skin depth. So a scaled antenna will generally perform very closely to, but not exactly like, the same antenna before scaling.
Segment Length Tapering
Note: The process of making an element from telescoping tubing is called
tapering by some authors, and corrections for NEC-2's inaccuracy in modeling these is sometimes called taper correction. EZNEC uses the term segment
length tapering or segment tapering to refer to the process of stepping, or tapering, segment lengths, rather than diameters. (The process of correcting
NEC-2 for steps in wire diameter is called stepped diameter correction.)
Multiple wires joining at an acute angle sometimes require shorter segments than single straight wires or wires joining in a line, particularly when a source or load is near the junction. This is seen with antennas such as multiple dipoles connected to a common feedpoint. Another case is with very low
. The straightforward solution in this situation is to increase the number of segments. However, doing so increases computation time. The technique described here provides high accuracy with a smaller total number of segments.
EZNEC User Manual
Instead of making the entire wires out of short segments, the segments can be made short near the junction, gradually increasing, or tapering, to a greater length away from the junction. EZNEC automates this process but it's useful to know how the procedure works so you can optimize it for your particular purpose. The basic procedure is to replace the original wire with several wires of different lengths. The new wire closest to the junction is made very short and with one segment. The second wire is made twice the length of the first, also with one segment. This process is continued until the segment length becomes long enough (say, 1/20 wavelength), and the remainder of the original wire is made up of a multiple-segment wire of approximately this segment length. In the automated process, you can choose the minimum and maximum segment lengths or use the default values of 1/400 and 1/25 wavelength.
This technique shouldn't generally be used if connecting wires have different diameters, unless perhaps when using an NEC-4 engine with EZNEC/4. See
Segment length tapering isn’t available (the menu choice will be grayed out) if
To length taper segments:
1. Save your antenna description. Segment length tapering is permanent and can’t be undone.
2. In the Wires Window, select Taper Segs in the Wire menu. This opens a dialog box.
3. Select the wire you want to taper, and which end of the wire is to be the end with the shortest segment length. The default maximum and minimum segment lengths are suitable for most purposes, but you can modify these values if desired.
4. The number of segments and wires which will be created by the process are shown in the dialog box. If this is ok, click Ok and the specified wire will be tapered.
The new collection of wires will be shown in the Wires Window with a distinctive color, so you can easily keep track of which wires you’ve tapered.
Tip: To create a group of tapered radial wires, create a single wire, then use
Segmentation Check detects some common violations of NEC modeling guidelines, namely segments which are too long or short, or segment length/diameter ratio out of bounds. Unless automatic operation is disabled via the Control Center Options menu, Segmentation Check is run whenever the program is started, a new description is opened, the frequency is changed, or wires are imported from an ASCII file. It can be run at any time from the Control Center Outputs menu. There are two sets of guidelines, conservative and minimum recommended. In general, you should keep your antenna within the minimum recommended guidelines, and observe the conservative guidelines if the antenna is narrow band or critical. Always be aware, however, that even this doesn’t guarantee a sufficient number of segments. See
, so you can save or print the data if desired.
If any errors are found, an additional menu, Segmentation, is shown in the
Editor. This allows you to have EZNEC automatically adjust the number of wire segments to conform to the NEC guidelines. The choices in this menu are as follows:
Fix Segs – Adjusts the number of segments only on wires which violate guidelines.
Auto Seg – Adjusts the number of segments on all wires to the minimum number required to meet guidelines.
Each of these selections has two additional choices, allowing you to adjust to conservative or minimum recommended guidelines (explained above).
Caution: Segmentation Check does not find all possible description errors, only the ones listed above.
EZNEC-M, EZNEC/4 only:
Wire grids created using the EZNEC pro
Window) with default spacing will show violation of conservative guidelines.
This is normal.
The velocity factor is taken into account when evaluating the segmentation of buried wires. This often generates warnings when segments are quite short.
(To see the velocity factor being used, click Ground Info in the Control Center
Utilities menu.) Ground loss is usually so high that coarse segmentation is adequate, so you shouldn’t be overly concerned about messages warning of too-short segments on buried wires.
Stepped Diameter Correction
A method used by EZNEC to correct for an NEC-2 inaccuracy when modeling connected wires of different diameters. Its applies only under a limited number of conditions, most notably full-sized Yagis made from telescoping tubing.
Stepped diameter correction isn’t necessary for EZNEC/4 using an NEC-4 calculating engine. See
for more detailed information.
The SWR sweep is run by first clicking the SWR action button in the Control
Center. If a sweep has recently been run and the model not changed since, you’ll be asked whether to view the existing data. If you choose No, or if there’s no existing valid data, you’ll see a dialog box which allows you to enter the start, stop, and step (increment) frequencies for the sweep. These values are shared by the
EZNEC read a list of frequencies from an ASCII text file. The requirements for this file are detailed in the
section. After entering your selections, click Run to begin the sweep. At the conclusion of the sweep, the SWR Display will open, showing the results. Use of this display is covered
section of the Reference chapter.
program directory. This file contains impedance results from the sweep, and persists after the program ends. The data in this file can be used for analysis by other applications if desired.
EZNEC User Manual
TraceView mode is a way to look at, compare, or print previously saved traces
(far field pattern plots) without having to run far-field calculations. TraceView mode is also capable of displaying some plot files in the OpenPF standard format generated by programs other than the EZNEC family, but this operation isn’t guaranteed. TraceView can also be used to translate plot files to .PF format from the .ENT format of ELNEC and EZNEC v. 1.
EZNEC can be put into the TraceView mode at any time by selecting
TraceView from the Control Center View menu. Alternatively, EZNEC can be started in the TraceView mode by entering <path>\EZW /TV in the Windows
Start/Run text box, where <path> is the EZNEC program path. If you use
TraceView frequently, you might want to set up a desktop shortcut to start
EZNEC in TraceView mode.
When TraceView first starts, you’ll be prompted for a primary trace file. This can be any current-version 2D or 3D EZNEC plot (trace) file having the extension .PF or .P#, or files from ELNEC and EZNEC v. 1 having extensions
.ENT or .F#, which you’ve previously saved. If you haven’t saved any plots from previous EZNEC calculations, there won’t be any to view with
TraceView, and TraceView can’t be used. The chosen plot can be viewed in the same manner as a regular EZNEC plot. Additional traces can be added to the 2D plot or “slice”, but only the primary trace field strength values can be shown in tabular form. The primary trace also determines the initial value of the plot outer ring if automatic scaling is chosen, and characteristics shown in the Control Center are those of the primary trace.
Menu selections and operation are the same in TraceView as for the standard mode, except that many menu items are missing (because TraceView is for viewing only), and the Open selection prompts you for a primary trace file rather than a description file. You can select a new primary trace at any time with the Open button or File menu item.
If the primary trace file is in ELNEC or EZNEC v. 1 format (.ENT or .F# extension), it can be saved as a .PF file by selecting Save Trace As in the 2D display File menu. This choice won’t be available if the primary trace file is already in .PF format.
You can end TraceView by ending EZNEC, or you can change to the normal mode by clicking TraceView in the Control Center View menu.
EZNEC v. 4.0 has unlimited undo/redo capability. This applies to all choices saved with the antenna description, but not to program-level changes like the selections in the main window Options menu. Undo/redo is done via the Edit menu in the Control Center and other windows, which can be used interchangeably. The maximum disk space used by undo/redo is generally modest by current standards, but it can be limited if desired, via the Control
Center Options menu Undo Disk Space selection. Undo is reset when a new description is opened. If the previous description has been changed, you’ll see a prompt asking you if you want to save it before proceeding. This prompt can be turned off via Control Center Options menu selection Messages
The Control Center
Control Center Introduction
The Control Center is as its name implies – the center and beginning point for all EZNEC operations. It appears when EZNEC first starts, and remains present until the program ends. It contains several distinct areas, shown below:
Information Window – This window shows information about a number of important parameters of the antenna being modeled. Any of the information in this window which can be changed is saved with the antenna description in the antenna description file.
Selection Buttons – These buttons allow you to change the item shown on the corresponding line. Buttons which don’t have a ‘>’ mark, or which have a dim mark, can’t be changed. Selections can also be chosen by clicking anywhere on the corresponding line in the Information Window. Most selections will open a dialog box or input grid. These functions are detailed in the
section. Note that the Title line above the Information Window is also one of the available selections.
EZNEC User Manual
Action Buttons – These buttons start various common actions, such as opening the View Antenna display or starting a pattern calculation. The function of each button is detailed in the
Menus – The menus contain a wide variety of items, most of which are program related. An exception is the selections in the Plot menu, which are saved with the antenna description. Each selection in each menu is described
The Control Center Menus
Control Center Menus Introduction
It’s important to note the unique function of the Plot, Setups, and Options menus.
The Plot and Setups menus are unlike the other Control Center menus in that choices made in these menu are saved with the antenna description file, just like the Information Window items. They will be restored each time you open that description file.
The Options menu contains items which apply to all antenna descriptions until
EZNEC is ended, at which time your choices are discarded unless you’ve selected Save As Default. Whenever you choose Save As Default, the last selection in the Options menu, all Options menu selections are permanently saved, and will be restored each time you start EZNEC.
Each selection of each of the menus is detailed in the sections which follow.
Open Description – Allows you to select an existing antenna description
(model). [EZNEC pro only]: To open an NEC format file, include the extension .NEC with the file name.
Save Description As – Allows you to save the current antenna description
(model) as a file. [EZNEC pro only]: To save a file in NEC format, include the extension .NEC with the file name.
Add Description – Allows you to select an antenna description (model) to
for more information.
Restore Default Folder – EZNEC remembers the last folder you used for opening or saving a description, so the next time you open or save a description, the last folder you used is listed as the initial choice. This selection resets the initial choice to the description file folder specified in the
Folders section of the Options menu.
Import Wires From ASCII File – This choice allows you to select an ASCII file containing wire coordinates, which will be imported into EZNEC. See
for more information, and
for the file format.
Add to Existing Wires – The wires in the ASCII file will be added to the current model.
Replace Existing Wires – The wires in the ASCII file will replace the wires in the current model.
Edit Current Antenna Notes – Opens the
file for the current
file to edit.
save the file under the same name, so the original file content is protected from modification. This is intended to be used for viewing EZNEC-related files such as frequency sweep output, ASCII wire coordinate files, etc., but it can be used for viewing any text file.
Edit File – Same as View File, above, except that the original file content isn’t protected, and you’re allowed to save a modified text under the same file name.
Exit Without Saving – EZNEC normally saves the current description in a file named Last.EZ, which it loads the next time it starts. However, if you select this choice, the current description won’t be saved. This is useful if the current description is defective, thereby preventing EZNEC from saving it, or if you’ve done a quick experiment but want EZNEC to start up the next time with the same description it started up with for the current session. Ends EZNEC.
Exit – Normal way to end EZNEC. Saves the current description in Last.EZ and ends the program. Does the same thing as clicking the close box in the upper right corner of the Control Center.
Undo, Redo – Allows you to undo changes made to the description since it was opened, and to redo any changes that were undone.
All selections in this section remain effective until the program ends. They can be made permanent (that is, they become the new default values) by clicking
Save As Default at the bottom of the list.
Angle Convention – EZNEC allows you to represent azimuth angles in either of two ways. Changing from one way to the other has no effect on the model, antenna view, or the graphics plots. The only effect is in the angles reported in various tables and data outputs.
Compass Bearing – Zero is in the direction of the +y axis (at the top of the 2D azimuth plot display). Angles increase as you go clockwise from zero.
CCW From X Axis – Zero is in the direction of the +x axis (to the right of the 2D azimuth plot display). Angles increase as you go counterclockwise from zero. This is the convention commonly used in mathematics and physics.
AutoComplete/AutoSuggest – Note: This selection doesn’t appear on
Windows 95, 98, or NT systems, since these systems don’t have the
AutoComplete or AutoSuggest features.
In the file selection dialog boxes, two automatic features can come into play on some Windows operating systems when certain Internet Explorer options have been chosen. One of these, AutoSuggest, appears as a drop-down list of files beginning with the same letters as any you have entered in the file name text box. The other, AutoComplete, automatically enters in the text box one of the selections from the list. Unfortunately, there’s no way to limit the suggestions or autocompletion to files with extensions appropriate for the purpose at hand. So there’s no way to guarantee that either the suggested or
EZNEC User Manual autocompleted file names are acceptable. AutoComplete, in particular, can be a nuisance if it selects a file name having an unacceptable extension. These features can be turned off (and on) in the Windows Internet Explorer Tools menu, and the settings there apply to all Windows applications. (Please refer to your Windows or Internet Explorer documentation for details.) The
AutoComplete/AutoSuggest option in the EZNEC Options menu allows you to choose separate settings for AutoComplete and AutoSuggest to be used by
EZNEC. As with all other Options menu items, these settings apply only until you end EZNEC unless you select Save As Default in the Options Menu after making your other selections.
Calculating Engine (EZNEC+ and EZNEC pro only) – Allows you to choose the engine used for calculations. The calculating engine choice is shown just above the FF Plot button in the Control Center.
EZCalc (NEC-2) – Internal NEC-2 calculating engine. This is a mixedprecision engine, doing some calculations in single precision and some in double. In most cases, its accuracy is equal to double-precision
EZCalcD, and it’s somewhat faster. For all program types except
EZNEC/4, it’s the best choice for general purpose use. In EZNEC/4, this engine would normally be selected only if comparisons are to be made between NEC-2 and NEC-4 results.
EZCalcD (NEC-2D) (EZNEC+ and EZNEC pro only) – Internal doubleprecision NEC-2 calculating engine. In most cases, its results will be the same as EZCalc. However, it will maintain accuracy in extreme cases such as very small loops, beyond the point at which EZCalc will begin to have difficulty. A difference between EZCalc and EZCalcD results generally indicates that EZCalc, and perhaps also EZCalcD, is encountering numerical difficulties. EZCalcD requires about twice the memory and disk storage that EZCalc does. This isn’t a concern with modern machines and moderate sized models, but with the very large models possible with EZNEC pro, this factor should be considered.
EZCalc4 (NEC-4) (EZNEC/4 only) – Internal single-precision NEC-4 calculating engine. This is recommended for general purpose calculations with EZNEC/4.
EZCalc4D (NEC-4D) (EZNEC/4 only) – Internal double-precision NEC-
4 calculating engine. This option requires twice the memory and temporary disk storage as the EZCalc4 option, and is slightly slower. It will give more accurate results in some situations, such as when very small loops or unusual geometry are involved.
External NEC-4 – Allows selection of an external NEC-4 program to be used for EZNEC/4 calculations. Some EZNEC/4 features, such as
MININEC-type ground and the ability to stop calculations before completion, are not available. Use of this selection is required only in
Default Ground Const – Allows you to enter values of ground medium conductivity and dielectric constant which will be used when you create a new ground medium. You might want to set these to reflect the properties of your local ground.
Folders – Allows you to specify the default locations of various files used by
EZNEC. To select a folder, double-click your choice. The folder name and path will appear under the white window, and the folder icon will show that the
Reference folder is open. Remember that your choice will be effective only until the program ends unless you select Save As Default at the bottom of the Options menu selection list.
Each of the following dialog boxes includes a Default Folder button. This will return the selection back to the folder which has been saved as the default value. It’s useful when you’ve selected a folder for temporary use and want to return to the normal default location.
Description (.EZ) and Plot Files – Default location of the description files and 2D and 3D plot files.
Ground Data Files – Location of the ground data files used for the
Real, High-Accuracy ground model.
WinSMITH or MicroSmith Files – Location of the winSMITH or
MicroSmith input files which EZNEC writes when doing a frequency sweep. This would normally be the folder where your winSmith or
MicroSmith program resides. Whether the title of this selection is
WinSmith Files or MicroSmith Files depends on the setting of the Smith
Chart Program selection in the Options menu.
Output Files – Location of the frequency sweep output file and other files generated by EZNEC (except the ones having their own folder options).
Temporary Files – A number of temporary files are written by EZNEC at various times, then erased during program execution or when
EZNEC ends. Some of these files can get quite large if your model contains a large number of segments. The initial setting for this choice is the temporary directory used by Windows, but you can set it for another directory if desired, or another drive if disk space is a problem with the default drive. This selection has an additional button, System
Temp Folder, to allow easy selection of the folder used by Windows for temporary files. This folder, which is the initial default used by EZNEC, is otherwise sometimes hard to find using the normal navigation tree.
Ground File Tolerance – When EZNEC does an analysis with Real, Highaccuracy ground, it checks to see if the necessary ground data have already been calculated and saved as a ground data file. Each file corresponds to a particular combination of frequency and ground conductivity and dielectric constant, so a file might already exist for a combination which is just slightly different than the current conditions. If the difference is small, the file data can be used with a negligible degradation of accuracy, and the time required to recalculate the data is saved. The initial default value of one percent is adequate for most use. If you’re doing many-stepped frequency sweeps, or other operations which cause frequent ground file calculation (indicated in the
at the beginning of calculations), and you have a slow machine, you might want to set the tolerance to a higher value. If you’re trying to resolve very small differences in patterns, particularly involving vertically polarized antennas where the ground characteristics are more important, you might want to set the tolerance to a smaller value, perhaps
0.1%. For extremely sensitive calculations, a setting of zero will force EZNEC to recalculate the data unless conditions match to within about five decimal places.
EZNEC User Manual
Messages On/Off – Allows you to suppress the “Description has changed” message when you open a new description, and the tooltips that appear when you pause the cursor over some controls.
Segmentation Check – This determines when the
will be run.
Auto – Automatically runs when a new description is opened, wires are imported from an ASCII file, or the frequency is changed.
Manual – Runs only when selected from the Control Center Outputs menu.
Printed Plot Line Width – Allows you to adjust the width of the lines in
of the Graphics
Windows, and only when printed. It has no effect on the screen display.
When the width is set to a value greater than one, lines normally shown broken (separate 2D polarizations; and View Antenna axes when offset from the origin, and current polarization markers) will be printed as solid. Broken lines can be forced to be printed with a width of one, however, causing them to be printed as broken, by means of the
Printed Plot Data Font – Selects the font to be used for printing the
display or on the Plot section of the printed output.
Power Level – If the Absolute V, I sources box is checked, voltage and current sources will have the values declared in the Sources Window. The total power applied to the antenna will then be determined by a combination of these values and the feedpoint impedances. If you uncheck the box and enter a non-zero value for the power level, all sources will be adjusted in proportion to result in the specified power being applied to the antenna. The specified power will be the total power from all sources, and it won’t vary with antenna impedance. The values shown in the Sources Window will represent relative, not absolute voltage and current values. The actual voltages and currents can be seen in the Source Data display. This is a powerful and useful feature for a number of applications.
Smith Chart Program – When EZNEC does a frequency sweep, it writes files which can be directly used by MicroSmith or winSMITH. This selection allows you to choose which format EZNEC uses. Note: Both programs limit the maximum number of frequency steps which will be accepted. See MicroSmith or winSMITH for more information.
Stepped Diameter Correction – Determines when
EZNEC, EZNEC+, and EZNEC-M only:
On (recommended) – EZNEC will use Stepped Diameter Correction when possible.
Off – EZNEC will not use Stepped Diameter Correction. This setting may lead to inaccurate results for some types of antennas, most notably Yagis having elements made from telescoping tubing.
NEC-2: On, NEC-4: Off (rec.) – Enables Stepped Diameter Correction when using the NEC-2 calculating engine only. Because the NEC-4 engines (internal or external) are relatively free from the stepped
diameter problem, Stepped Diameter Correction is disabled when one of these engines is selected.
Always off – Stepped Diameter Correction is always disabled. This setting may lead to inaccurate results for some types of antennas, most notably Yagis having elements made from telescoping tubing.
Always on – Stepped Diameter Correction is always on. This would not generally be chosen unless it was desired to see its effect in NEC-4.
Undo Disk Space – Allows you to limit the amount of space used for the
Undo feature. Storage requirements are very modest, so this can normally be set to Unlimited.
EZNEC Geometry Check – NEC allows wires to cross at segment junctions.
While it’s discouraged for EZNEC models (primarily because the connection will be broken if segmentation is changed), no error will occur if this situation exists. Some models originally designed to run under NEC-2 or –4 have numerous segment junction crossings. This menu selection allows you to prevent warnings of this situation from appearing in the Geometry Check output.
Pre-Calc Geometry Check (EZNEC/4 only) – Allows you to choose whether
EZNEC runs its own geometry check, uses the NEC-4 SEGCHK check, or both. EZNEC’s check catches some errors which SEGCHK misses, and it’s faster, so this selection should normally be left in the default condition
(EZNEC geometry check) unless there’s some special reason to change it.
Far Field Table Units – Selects the units used in the
have no effect on any other outputs or displays.
EZNEC, EZNEC+ only: dBi or dBref – Shows field strength in dBi or, if a non-zero dB reference is chosen (see below), in dB relative to that reference. mV/m for 1 kW at 1 mile – Shows the field strength in mV/m at a distance of one mile, for an applied power of 1 kW. Note: When this option is selected, the Power Level selection (above) is not used for the
Far Field Table. mV/m for 1 kW at 1 km – Shows the field strength in mV/m at a distance of one km, for an applied power of 1 kW. Note: When this option is selected, the Power Level selection (above) is not used for the
Far Field Table.
EZNEC-M, EZNEC/4 only:
The units which are displayed depend on whether
have the same effect as those above. The choices for units with ground wave analysis are: mV/m – Output in mV/m at the distance specified as the Control Center
Gnd Wave Dist. If the power level has been specified using the Power
Level selection (above), this power is used; if not, the power resulting from the absolute source voltages and currents is used. dBi or dBref – Same as the corresponding non-ground wave choice.
Near Field Table Format – Selects whether near field phase information is to be shown. The narrow format output doesn’t include phase information, and may produce a more easily readable output when viewed or when printed to a portrait-oriented page. This setting affects the output saved in the
EZNEC User Manual
2D Plot Scale – This allows you to choose between two types of scale for the
ARRL Type – This scale is the standard scale used by the ARRL and in many amateur publications. It’s a logarithmic-dB scale which shows the pattern maxima with greater detail at the expense of compressing minor lobes. This scale is generally recommended for amateur use because the plots will be more easily compared to published ones.
Linear dB – As the name implies, this is a plain dB scale, linear with respect to dB. It extends 40 dB from the outer ring to the center of the scale. Although the outer ring value in dBi is adjustable, the range from the center to outside is not.
Show Freq on 2D Plot – When this option is on (checked), the frequency is shown at the lower right side of the 2D plot display. Note that the frequency won’t be shown at the lower right when the results of a frequency sweep are being shown.
Default 3D Step Size – EZNEC 4.0’s minimum step size of one degree is too fine and slow to draw when doing general purpose 3D plotting. This menu selection allows you to set the default step size when a 3D plot type is initially chosen.
View Antenna Wire Numbers – Selects whether the wire numbers are shown when you first start the
appear centered on the wires or offset. You can change these choices in the
View Antenna Display, but that setting cannot be made permanent, while this setting can.
Initially On – Wire numbers are on when you first start View Antenna.
Initially Off – Wire numbers are off when you first start View Antenna.
Use this setting if you frequently work with complex models, where the wire numbers overlap and become unreadable.
Initial Position – Selects whether the wire numbers are initially centered over the wires or are offset.
Save As Default – Clicking this choice makes all the values selected in the
Options menu permanent. Unless it is clicked, any changes made will be discarded when EZNEC ends. Any changes made after it is clicked will likewise be discarded at the end of the session unless it is clicked again to save the changes.
Geom and Seg Check – Runs both the Geometry and Segmentation checks
Segmentation Check – Runs the
, which checks the model for violation of several NEC guidelines.
Geometry Check – Runs the
, which detects a number of conditions that aren’t allowed, such as wires overlapping, or intersecting or crossing at other than a wire end or segment junction.
Show Description – Shows a summary of the antenna description as plain
. This includes wire coordinates, source and load locations, etc. The displayed description can be printed or saved to a file.
A similar display, with only the wires coordinates, is available in the
Frequency Sweep – Opens the frequency sweep setup dialog, to set up parameters for the
Near Field – Opens the near field setup dialog, to set up parameters for
mode, for viewing, printing, or comparing saved far-field pattern plots (traces) without having to do any calculations.
Edit .INI File – A number of
can be enabled by entering statements in the EZNEC.INI file in the EZNEC program directory. These are generally options which are seldom used, or are used only for special purposes. This selection opens the EZNEC.INI file in the
for easy modification. Most changes made to the EZNEC.INI file aren’t effective until EZNEC is exited and re-started. If you edit the EZNEC.INI file and want to apply the changes, save the file, exit EZNEC, allow a minute or so for the disk cache to write saved information on the disk, and re-start EZNEC.
Show Calculation Time – Shows the times which were taken for various calculations. No numbers will be shown until EZNEC completes a calculation.
Note: When a frequency or SWR sweep is run, only the time for the last frequency calculation is shown, not the time for the entire sweep.
Show Ground Info – Gives detailed information about ground characteristics when Real ground type is selected.
Show Memory Info – Gives information about available computer memory.
This report is directly from the Windows system, and might not agree with some other analysis tools. Note that it’s not uncommon for the available memory (RAM) to be at or near zero; Windows routinely uses the disk as virtual memory, and frees up RAM as needed.
Show Temp Dir Space – This shows the approximate amount of temporary space which will be required by the calculating engine to run calculations for the current description, and the amount available.
Component Version Numbers – Shows the complete version numbers of each of the major components of EZNEC.
Contents – Opens this help file and shows the contents.
About EZNEC – Shows the program version number and copyright and trademark notice.
Information Window and Action Buttons
Control Center Selections
All selections in the Control Center Information Window are part of the antenna description and are saved with the antenna description (.EZ) file. Selections made in the Setups menu are also saved with this file.
Title – This selection isn’t marked except with a > symbol. It’s the gray bar just above the white Information Window, and contains the title of the
EZNEC User Manual description. Clicking anywhere on this line opens a dialog box for you to enter a title for your antenna model.
File – Shows the name of the last file saved or opened. This is for information only and can’t be changed.
Frequency – Shows the current frequency, or if
Click this to change the frequency or
Wavelength – Shows the wavelength in current units. This is for information only and can’t be changed.
Wires – Shows the number of wires and segments in the model. Clicking opens the
Sources – Shows the number of sources in the model. Clicking opens the
Loads – Shows the number of loads in the model. Clicking opens the
Trans Lines – Shows the number of transmission lines in the model. Clicking opens the
, for adding, deleting, or modifying transmission lines.
chosen. Clicking it allows you to choose the ground type.
models is chosen. It shows how many ground media (1 or 2) have been defined, and their conductivities and dielectric constants. Shows
if specified. Clicking opens the
characteristics and NEC radials.
opens a dialog box allowing you to specify a wire loss characteristic.
Units – Shows which primary unit of length you’ve chosen. Clicking opens a dialog box allowing you to choose the primary units of measure.
Plot Type – Shows which plot type – azimuth, elevation, or 3 dimensional, you’ve chosen. Clicking opens a dialog box allowing you to choose the plot type. EZNEC pro only: When
is active, this option is fixed at Azimuth, the only type allowed with ground wave analysis.
Elevation Angle, Azimuth Angle or Bearing, or Observation Height – This selection isn’t available when 3D Plot Type is specified. When doing an azimuth plot, it shows and allows you to choose the elevation angle for the 2D azimuth plot. When doing elevation plot, it allows you to choose the azimuth
is active, shows and allows you to choose the height of the observation point.
Step Size – Shows and allows you to choose the angular increment for the
2D or 3D plot.
Ref Level – All outputs showing field strength will be relative to the value shown here. If you want, for example, to show gain relative to the gain of a dipole in free space, set this value to 2.15 dBi. (This choice is meaningful only when doing free-space analysis. As shown in the
, a dipole mounted over ground exhibits gain several dB greater than this amount.
Alt SWR Z0 – Various displays show or output SWR assuming a 50 ohm system and a second impedance of your choice. This is where you choose the second impedance. A typical use would be an antenna fed with 50 ohm
Reference line through a 4:1 impedance step down transformer. If you set the Alt SWR
Z0 to 12.5 ohms, the indicated SWR is what you would see on that 50 ohm line.
Desc Options – This selection allows selection of several properties which are saved with the description file. Under the General tab, you can choose to have the Geometry Check ignore the situation where the center of a segment is within another wire. This sometimes can’t easily be avoided and, while it sometimes causes erroneous results, it often doesn’t. See the
plot choices, including polarizations to show on the 2D plot.
Gnd Wave Dist – [EZNEC pro only] Shows the horizontal distance to the
observation point. Clicking it allows you to select the distance and to turn ground wave analysis on and off.
Several of these actions are explained in more detail in the Interpreting The
Open – Click this to open a different antenna description file. Note: All
unsaved information in the existing file will be lost. Save your existing
description if you want to preserve it. [EZNEC pro only]: To open an NEC format file, include the extension .NEC with the file name.
Save As – Click to save your current antenna description. [EZNEC pro only]:
To save a file in NEC format, include the extension .NEC with the file name.
Currents – This opens the
wires in tabular form, running a calculation if necessary.
Src Dat – Opens the
power, impedance, and SWR at each source, running a calculation if necessary.
Load Data – Opens the
power, and impedance of each load, running a calculation if necessary.
in tabular form, running a calculation if necessary.
output, which shows the near field strength in tabular form, running a calculation if necessary.
SWR – Opens a dialog box so you can define the sweep parameters for the
View Ant – Opens the
, which gives you a 3 dimensional view of the antenna.
The Graphics Windows
Graphics Windows Overview
The 2D Plot, 3D Plot, View Antenna, and SWR displays have a number of common features, so all are grouped together here. They are collectively called the Graphics Windows.
All Graphics Windows can be sized by dragging an edge or corner, or can be maximized or minimized by use of the controls in the upper right corner of the form. Minimum sizes apply to some forms, limiting the size adjustment range.
EZNEC User Manual
Graphics Windows Sections
The Graphics Windows are divided into sections, as shown below. Not all
Graphics Windows contain all three sections. The Control Box section of the
2D Plot Display, which is shown below, is available only when the 3D Plot
Display is also on. The Data and Control sections can be turned on or off via the menu File selection.
Plot or Display
The Plot or Display section contains the actual graphical information being displayed.
The Data section contains additional information about the plotted data.
The Control section contains controls to alter the Plot display.
Graphics Windows Menus
All Graphics Windows have all or most of the following Menu selections. The selections function the same for all displays, except for exceptions noted below.
sized to print the page; its size isn’t adjustable. The line width of the Plot
of the window on the printer. The Data text is printed below the plot. The line width of the Plot section and the font used for the Data section can be adjusted from
Printer Setup – Opens a dialog box allowing you to choose the printer and paper type and characteristics.
Add Trace (2D only) – Opens a dialog box allowing you to choose a trace to add to the existing display. At present, the detailed information in the Data section is available only for the primary trace. The colors of added traces can be selected via the 2D display Options/Colors/Recalled Traces selection, described below. Trace types which can be added are:
.ENT – 2D Trace files created by ELNEC and EZNEC family products prior to v. 2.0.
.F# -- 2D Trace files created by ELNEC and v. 1 EZNEC family products frequency sweeps.
.P# -- 2D Trace files (OpenPF format) created by v. 2 and later EZNEC family products frequency sweeps.
.PF – 2D trace files (OpenPF format) created by v. 2 and later EZNEC family products.
.PF3 – 3D trace files (OpenPF format) created by v. 2 and later EZNEC family products.
Remove Trace (2D only) – Removes traces added via the selection above.
Clicking this option opens a list of added traces. Clicking on an item in the list will remove that trace. This selection isn’t available if no traces have been added.
Save Trace As (2D), Save 3D Plot (3D) – Use this selection to save the 2D or
3D trace. A 2D trace can be added to a later display for comparison. Either a
2D or 3D trace file can be opened in TraceView mode as a primary trace. The plot will be saved in OpenPF format with a .PF (2D) or .PF3 (3D) extension.
Show Added Trace Info (2D only) – Shows additional information about added traces. This selection is disabled if no traces have been added.
Restore Default Folder (2D, 3D only) – When you save a 2D or 3D trace or add a 2D trace, EZNEC remembers the last directory you chose and takes you there when you open the file choice dialog box. If you’ve navigated your way to some obscure directory and want to return to the directory where you normally store trace files, click this selection before choosing Add Trace or
Save Trace As. This selection returns the initially displayed directory to the one chosen in
Folders/Description (.EZ) and
Plot Files selection.
Undo – Allows you to undo any change you’ve made to the description since opening it, in reverse sequence to the order in which the change was made. A change made anywhere in the program can be undone from any window having an undo selection.
Redo – Allows you to redo changes which have been undone.
Copy Plot – Copies the
of the display to the Windows Clipboard as a bitmap. This allows it to be pasted into any Windows application which can accept graphical objects. Unlike the Print Plot selection above, the plot is not redrawn to a larger scale; the plot is copied exactly as it is. If the copy is later enlarged, quality will be poor because of the limited number of pixels in the original. It’s best to adjust the EZNEC plot size to the actual size desired for the copy before creating the copy. Alternatively, you can first maximize the plot by clicking the maximize button near the upper right corner of the window.
EZNEC User Manual
For best resolution, turn off Controls and Data sections (via the View menu) if on. Then do the copy. The resulting copy will have the highest possible resolution, and many applications will be able to reduce it to the desired size while retaining high quality.
of the display to the Windows Clipboard as a bitmap. See the above comments regarding quality. This selection isn’t available if the Data section is turned off.
(The Data section can be turned on via the View menu.)
Mult Trc Field (2D only) – This choice is enabled only when one or more
choice has been made to plot multiple polarizations, for example Vert, Horiz, Total. Only one polarization can be shown when the display has multiple traces. This menu selection allows choosing which of the polarizations to show.
Show 2D Plot (3D only) – Turns the 2D Plot Display on and off. This allows viewing and detailed analysis of any 2D “slice” of the 3D plot.
of the display on and off. NOTE:
This isn’t available for the 2D display unless a 3D display is on, with a “slice” of the 3D plot being shown on the 2D display.
of the display on and off.
Show Data Lines (2D only) – When on (checked), lines are added to the 2D display, showing the directions of the pattern maximum, -3 dB points, and sidelobe, as reported in the data box. This option is available only if the Show
Data option is checked. Colors for these lines can be chosen in the Options menu.
Show Objects (View Antenna only) – Allows you to select which of various objects is displayed in the
of the display, such as currents, segment dots, etc. These are detailed in the
Colors – Allows you to choose the colors for objects displayed in the plot section of the display. NOTE: Choices will persist only until the program ends, unless the Colors menu is re-opened and Save As Default is clicked. Also allows resetting choices to the saved default colors. NOTE: Background color choice is ignored when printing.
Reset (2D, 3D, View Antenna only)
Reset Cursor to Max (2D, 3D only) – Resets the cursor to the point of maximum field strength. In the 3D display, this option isn’t available unless highlighting is on, and the highlighted slice is also returned to the one containing the maximum field strength.
Reset Position (View Antenna, 3D only) – Rotates display to the default position.
Reset All (View Antenna, 3D only) – Resets position, and all other choices such as zoom (but except colors) to initial values.
Creating Graphics Files
EZNEC does not directly create graphics files in common formats like .bmp,
.gif, or .jpeg. However, it’s still easy to do. In any of the Graphics Windows, open the Edit menu, then select one of the Copy options. This will copy the current display to the Windows Clipboard. Open a graphics application such as Paint, which is furnished with Windows, and paste the Clipboard contents into it. The graphic display can then be saved to a file in any of the formats available in the graphics program. Of course, it’s not necessary to save or convert the graphic display in order to insert it into a word processor or other application. It can simply be pasted there directly from the Windows
Clipboard. For tips to get the best quality of saved or pasted graphic display,
Note that .pf format files saved as “trace files” are not graphics files. They are binary files which contain only numerical field strength data, and no information about how to plot or display it.
Using The View Antenna Display
The View Antenna display is one of EZNEC’s most useful displays. With it you can see what the antenna looks like and see changes as they’re made, look at the currents on each wire, see how the pattern is oriented relative to the antenna, and much more. You’ll find it useful to leave this display open most of the time.
The display window shows, to scale, what the antenna looks like. Various objects can optionally be shown on this view in addition to the antenna, as described below.
The Data Window
The Data Window, under the display, shows the length and segment length of the most recently selected wire. It can be turned on and off via the Show Data selection in the View menu.
The Control Window, to the left of the display, can be turned on and off via the
Show Controls selection in the View menu. It has controls enabling you to zoom, center, and move the image, and zoom the displayed currents after running a calculation. Moving or zooming the display have no effect on the
antenna model. They only change the way you’re looking at it. Note that you can also move and zoom the display (but not the currents) with the mouse.
See Mouse Operations, below.
The Axes – When an antenna is first viewed, the intersection of the axes represents the coordinate system origin. If you move the antenna with the controls or by clicking the Center Ant Image box in the Control Window, the axes no longer represent the absolute coordinate system. When this is true, they become broken rather than solid. The origin marker (a dot surrounded by a circle) continues to show the true position of the origin even when the display is moved or zoomed.
Rotating - To rotate the display, position the mouse cursor anywhere on the display window. Press and hold down the left mouse button. You can then rotate the display in two directions by moving the mouse while the left button
EZNEC User Manual is held down. Although the mouse cursor must be on the display window when the button is first pressed, it can be moved outside the window if necessary while the button is down. You can use the keyboard arrow keys for fine rotational positioning, but only after clicking in the display window to give it the focus.
Moving – To move the display, position the mouse cursor anywhere on the display window. Press and hold down the right mouse button. You can then move the display. It will move in the direction of one of the axes, the one most closely parallel to the mouse movement, so you might have to rotate the display in order to achieve movement in the direction of a particular axis.
Zooming – To zoom the display, position the mouse cursor anywhere on the display window. Press and hold down the both mouse buttons. This does not zoom the currents; that can be done only with the scroll bar.
If either the Wires Window or the View Antenna Data Window is open, the wire closest to the mouse cursor will be selected when the left mouse button is double-clicked. If the Wires Window is open, additional wires can be selected by pressing and holding the <Ctrl> key while clicking with the left mouse button. <Ctrl>-clicking a selected wire will deselect it. Double-clicking a wire will always deselect all other wires.
The View Antenna display and Wires Window are coordinated. Whenever the
Wires Window is on, wires selected in the Wires Window will be automatically selected in the View Antenna display, and vice-versa.
The length and segment length of the most recently selected wire appear in the View Antenna Data Window.
You can see information about any wire by pausing the mouse cursor over the wire. One important use of this feature is identifying which end of the wire is which – among the information shown are the coordinates of the wire end closest to the cursor, and that end is identified in the display. The behavior of
A number of objects can be added to the basic View Antenna display. These objects can be turned on or off via the Objects selection in the View menu.
Following is a description of each choice you see when you make this selection. All items are on (shown) when its corresponding box is checked.
Axes – Selects the axes.
Currents – Adds currents to the display. Current magnitude is indicated by distance of the current indicator from the corresponding wire. This is a very useful feature in determining which parts of the model are contributing to the pattern. Currents aren’t shown until a calculation has been done.
Current Phase – Modifies the current display to show phase by rotating the current lines around the wires. This is sometimes useful in conjunction with the Current Phase Markers (particularly when looking at phased arrays), but it often only obscures the current magnitude information.
Current Phase Markers – Added markers which can be selected if Current
Phase is on. These markers show a solid line in the direction of zero phase and a dashed line in the direction of +90 degrees. These help show the current phase when Current Phase is being shown.
Segment Dots – Turns segment and wire junction dots on or off.
Transmission Lines – Sometimes a transmission line is connected to a faraway wire. If shown, this would scale the antenna view in an undesirable manner. So transmission lines can be prevented from being viewed.
Wire Numbers – These are very useful when building, modifying, and troubleshooting a model. However, with a complex unzoomed model, they become an indistinguishable mass. The setting of the wire numbers is remembered until you quit EZNEC. The state of the wire numbers when you first start EZNEC can be set with the Control Center Options menu View
Antenna Wire Numbers selection. You might want to make the initial state be off if you commonly model complex antennas. The wire numbers can be centered on the wires or offset.
2D Pattern – once calculated, a 2D pattern can be added to the display. This is particularly useful in showing the orientation of the plot to the antenna. If
“Semi-Solid” is chosen, lines are added to give you a better idea of the real pattern shape and what it represents. The 2D plot won’t appear if a 3D plot has been run and no slice is highlighted.
Using The 2D Display
The 2D Display shows the result of a far field azimuth or elevation pattern calculation, which is a “slice” of the actual full three dimensional antenna pattern. It can also be used in conjunction with the 3D Display to show an elevation or azimuth “slice” of the 3D plot. This display automatically opens when a 2D (azimuth or elevation) pattern calculation is requested with the
Control Center FF Plot action button. To use the 2D plot to show a “slice” of the 3D pattern, open the 2D Display from the 3D Display View menu, or check the Show 2D Plot box in the 3D Control Window.
Many of the menu items are the same as for the other graphics displays, so they’re covered in a separate section
look this section over, because it explains how to do such things as add traces to the display. This makes it easy to compare antennas and plots and see the results of changes.
The 2D plot can include Data Lines and a Cursor. Neither of these is shown if the Data Window is turned off via the View menu.
Navigation and Advanced Features
EZNEC 4.0 has a number of features to help you analyze 2D antenna patterns. If you’ve chosen to display multiple polarizations, for example Horiz,
choice in the Control Center, you can move the cursor from one polarization trace to another simply by clicking its name in the key list at the left of the 2D plot window. The Data Window (see below) reports the field strength (as gain relative to isotropic) of that polarization component. If you add traces, you can switch the cursor to any trace by clicking the corresponding file name in the key list at the left of the 2D plot window. When this is done, and additional line of data appears in the right column of the Data Window, showing the gain of that trace relative to the primary (calculated) trace at the cursor’s angle. This makes quantitative pattern comparisons simple.
shows useful information about the 2D plot: maximum gain, front/back or front/side ratio, 3 dB beamwidth, and other parameters. The items on the right side of the window show the values at the cursor, so
EZNEC User Manual change as the cursor is moved. The cursor is moved by clicking anywhere on the Plot Window, and the plot cursor will move to a point on the direct line between the placed clicked and the center of the plot graph. You can drag the cursor around the plot by holding the mouse button down as you move the mouse. The mouse has to be on the
when initially clicked, but can leave the window afterward if the button is held down. The cursor is always present when the Data Window is open, and never present when it’s closed.
The up and down keyboard arrow keys can be used to move the cursor in small steps, and the <PageUp> and <PageDown> keys to move it in larger steps. It’s first necessary for the Plot Window to have the focus. It can be given focus by clicking anywhere on it with the mouse.
The Data Lines show the angles at which EZNEC has determined the maximum forward gain, -3dB points, and sidelobe occur. The “sidelobe” is the lobe with second highest gain. Data Lines can be turned on and off from the
View menu, and won’t appear if the Data Window isn’t being shown.
The Control Window is opened from the View menu. However, it’s not accessible unless the 3D plot is also open, since the controls are used primarily to select slices for display. When open, the controls in the Control
Window are the same as those in the 3D Control window, and the two sets of controls track.
Whether to show the frequency on the plot can be chosen in the Control
Center Options menu.
Using The 3D Display
The 3D Display opens automatically after running a far field pattern calculation when the Plot Type is 3 Dimensional. It shows a full pattern plot.
To make the plot easier to visualize, you can highlight any azimuth or elevation “slice”, and easily see its shape and where it fits into the overall pattern. The highlighted slice can optionally be shown in the 2D Display or superimposed on the View Antenna display.
Many menu operations are common among all the graphics displays, so
Rotating the 3D pattern
The 3D pattern is rotated in the same way as the View Antenna display, by holding down the left mouse button while you move the mouse.
Highlighting a slice
View menu and select either Azimuth Slice or Elev Slice. The 3D plot will dim, and the highlighted slice will be shown in a distinctive color. You can select the slice and move the cursor with the scroll bars. Note that you can also drag the scroll bar slider bar.
Displaying a 2D slice
If you check the Control Window Show 2D Plot box, the 2D Display opens and shows the highlighted slice. If the 2D Control Window is shown, the 2D controls will track the 3D controls. This combination of 2D and 3D plot combines detailed analysis with easy visualization.
If you open the View Antenna Display, you can add the 2D slice to the display via the View Antenna View menu Objects selection. It will move as you
Reference change the 3D slice. The 3D and View Antenna display also always face the same direction as soon as you release the mouse button.
Using The SWR Display
The SWR Display is shown after running an SWR sweep. This in turn is started by clicking the SWR action button in the Control Center, then entering frequencies or an input file name and starting the sweep as described in the
section. This section describes use of the resulting display.
Many menu operations are common among all the graphics displays, so
As the name implies, the SWR Display shows a graph of SWR vs. frequency.
The SWR is not necessarily the actual SWR on a transmission line, but is the
SWR which would be on a line if the line were connected between the source and antenna.
If you turn on the Control Window via the View menu, you’ll have a choice of the SWR for two values of line characteristic impedance (SWR). One impedance is 50 ohms. The other can be changed to a value of your choice by clicking on the Alt SWR Z0 line in the Control Center Information Window.
Also in the Control Window is a selector allowing you to choose the source for which to display the SWR, in the event your model has more than one source.
Additional information appears in the Data Window below the plot. The Data
Window is turned on or off from the View menu. In this window, you can see the impedance and reflection coefficient as well as the SWR.
The cursor can be moved by clicking on the display window or by dragging with the mouse. You can also use the arrow keys, after clicking once on the display window with the mouse to make sure the display window has the focus.
EZNEC Pro Information
EZNEC Pro Section Note
The information in this chapter applies only to EZNEC pro programs EZNEC-
M and EZNEC/4.
EZNEC Pro And NEC
This section applies only to EZNEC pro programs EZNEC-M and EZNEC/4.
There currently are two programs in the EZNEC pro family: EZNEC M and
EZNEC/4 can use an included enhanced NEC-2 calculating engine, a usersupplied NEC-4 calculating engine, or an enhanced NEC-4 engine supplied with EZNEC/4. EZNEC M can use only the included enhanced NEC-2 calculating engine. This is the only difference between the two programs.
Although EZNEC pro uses NEC-2 or [EZNEC/4 only] -4 as a calculating engine, there are several significant differences.
Voltages and currents: NEC uses peak values for voltages and currents.
EZNEC pro interprets and reports values in RMS. An NEC input file having a
1.0 volt source, when read by EZNEC pro, will result in an EZNEC pro source of 0.707 volts. Similarly, the currents reported by EZNEC pro will reflect RMS values. The power reported by EZNEC pro is the same as that reported by
NEC. (EZNEC/4 communicates to the NEC-4 calculating engine via standard
EZNEC User Manual
NEC input and output files. If you view the NEC input file created by EZNEC/4 and the output file created by the NEC-4 calculating engine, you’ll see the translation in value that takes place.)
Data input: Instead of editing an ASCII file, descriptions are entered via a spreadsheet-like entry system. This allows very easy modification, and the ability to immediately see the result on the antenna structure. (Note, however, that EZNEC pro can
from a simple-format ASCII file.)
NEC features: Not all NEC features are implemented in EZNEC pro. Those not implemented include symmetry, networks, patches, non-air primary medium, arcs, and catenary wires. EZNEC pro is chiefly oriented toward the analysis of wire antennas.
Files: Although EZNEC pro can read and write NEC-format description files, some functionality may be lost if this format is used exclusively. Full features are available only with EZNEC-format (.EZ) files. The binary format of these files is available on request.
Angles: EZNEC pro uses elevation angle in place of zenith angle. Elevation angle is measured upward from the horizon (XY plane). EZNEC pro also permits an alternate method of displaying azimuth angle. This corresponds to compass bearing, and is measured clockwise from the +y axis. The choice is
Power: In NEC, all voltage sources are absolute. EZNEC pro permits you to specify a particular power level. If this is done, all voltage and current sources will be adjusted in proportion to obtain the specified total power. This is useful for determining, for example, voltage stress on or power dissipation of loading components under actual operating conditions, or of near field strength resulting from a specific power input. The power level is specified in the
Average Gain: EZNEC pro reports an average gain of 1.0 (0 dB) whenever the integrated total radiated power equals the power supplied from the sources, whether or not ground is specified. The NEC value of average gain varies with the region specified for the radiation pattern, and equals 2 when radiated and input powers are equal and ground is specified.
Working With NEC Format Files
This section applies only to EZNEC pro programs EZNEC-M and EZNEC/4.
Writing files in NEC format is relatively straightforward. To save a description in an NEC format file, simply include the extension .NEC when you specify the file name. The remainder of this section deals with reading NEC format files.
To import an NEC format file into EZNEC pro, include .NEC as the extension when you specify the file name.
A number of NEC features aren't implemented in EZNEC pro, so exact translation of all files can't be done. However, many files can be directly translated, and most geometry cards, which usually constitute the majority of complex files, will be translated.
NEC file "cards" are interpreted per NEC-2 standards (to be compatible with both NEC-2 and NEC-4 files) except as noted below:
CE,CM The first 30 letters of the first CE or CM card becomes the title.
EK When using the NEC-2 calculating engine, EZNEC pro normally sets the extended thin wire kernel automatically depending on wire diameter; this card will override the internal setting. It has no effect when using an NEC-4 engine.
EN Terminates file translation.
EX Any source type except type 0 (applied E field source) will be converted to type 0. The magnitudes of all sources are divided by the square root of two to convert from NEC's peak convention to EZNEC pro's RMS convention. This is done so that powers reported by the programs will agree.
FR Frequency step data will be ignored. Frequency stepping must be manually set in EZNEC pro's Frequency Sweep Menu.
GA If more than one GA card have the same tag number, sources, loads, etc. applied to that tag number will only be placed on the arc defined by the first GA card with that tag number. EZNEC pro will assign individual wire numbers to each one-segment wire making up each arc.
GD, GN All parameters are translated. If a second medium is defined on both cards, the last card read will dominate. A radial ground screen will be ignored if only one medium is defined; if two are defined and the boundary is radial, the ground screen perimeter will be set equal to the boundary between the media. Please see additional GD, GN,
RP comments below.
GE The I1 specification will be ignored. EZNEC pro automatically sets the equivalent value to 0 when no ground plane is present, 1 if a ground plane is present and no wires extend below the ground, and -1 if any wires do extend below a ground plane. (Calculation for the latter case will be permitted only if EZNEC/4 is being used with an NEC-4 calculating engine and Real, High-accuracy ground has been selected.)
GM Only entire wires will be operated on. If a specified segment does not fall on a wire end, the whole wire containing that segment will be included in the operation. The tag increment number ITG1 is ignored, and new wires assigned numbers in accordance with
EZNEC pro's method.
GN GN 0 (reflection coefficient type ground) will be converted to High
Accuracy (Sommerfeld) ground type. EZNEC v. 4.0 doesn’t support reflection coefficient type ground.
GR Tag increment number ITG1 is ignored, and new wires assigned numbers in accordance with EZNEC pro's method.
GS The coordinates and diameters of all wires which have been read prior to encountering the GS card will be multiplied by the third parameter on the line (FSCALE).
GW Tag numbers are ignored. Wires are sequentially numbered. Sources, loads, and transmission lines will, however, be placed on the proper wires.
GX Tag increment number ITG1 will be ignored, and new wires assigned numbers in accordance with EZNEC pro's method.
LD LD type –1 (reset loads) isn’t translated. If some loads are R+jX (type 4) and others RLC (types 0-3) or wire loss (type 5)
, the EZNEC pro
EZNEC User Manual load type is set to RLC and the R+jX loads are converted to series
RL or RC. The impedances of these will vary with frequency, unlike the original NEC R+jX loads. The EZNEC pro load type will be set to R+jX only if there are no RLC or wire loss loads in the NEC file.
Loads with per-unit-length specifications (types 2 and 3) are calculated for the lengths of segments they’re initially placed on. But if segment lengths are subsequently changed in EZNEC pro, their values won’t change. Wire loss LD cards (type 5) are converted to
RL loads with a frequency-variable R, which varies in the same manner as wire loss
. The L won’t change with frequency, although this is generally a minor effect with wires. Remember, though, that these are now EZNEC pro loads, not wire loss. Their values will be correct for the wire diameter and segment length of their initial positions, but won’t change if diameter or segment length is subsequently changed. Repeated loads are placed using the same convention as NEC.
Note: LD5 “card” translation can be inhibited if
NE, NH Only the first NE or NH card will be read. The information contained on the card will be entered in the EZNEC pro Near Field Setup
Menu. Note: The convention for phi and theta is reversed between
NEC-2 and NEC-4. EZNEC pro uses the NEC-4 convention. A caution is shown in the translation window when these cards are encountered.
NX Terminates EZNEC pro translation.
RP EZNEC pro will ignore requests to print major, minor axis gains or do field normalization, directive gain, or gain averaging. Please see additional GD, GN, RP comments below. If no RP card is present, default values will be entered.
TL Shunt loads will be ignored.
XQ Any value other than 2 is interpreted as being 1, since EZNEC pro can’t do simultaneous plots.
All other cards are ignored.
Translation of the input file will terminate after the first EN or NX card is read.
Additional GD, GN, RP comments: Due to the complex interaction of ground specifications among GD, GN, and RP cards, EZNEC pro may not interpret the ground specification in the same way as NEC does. Be sure and check the ground type and specification after reading an NEC file. This is especially true when using the NEC buried radial (radial ground screen) model.
When EZNEC pro is forced to interpret a card in a different way than NEC, it will add a notice to the display shown at the end of the translation.
EZNEC pro disregards the positions of data on the line. Fields are delimited by spaces, tabs, or commas. Any number of spaces or tabs may be used. A field is considered blank or zero if it is surrounded by commas. For example,
'3 , ,51,4' is interpreted as four fields of value 3, 0, 51, and 4. Spaces and tabs are ignored unless characters other than commas are separated by only spaces or tabs, in which case the spaces/tabs are interpreted as a delimiter.
For example, '3 15,, 7 42 ,' will be interpreted as having fields of value 3, 15,
0, 7, 42, 0.
Comments can be added to individual lines if desired by delimiting with an exclamation point (!). Anything following an explanation point on any line will be ignored.
Please note: Partial translation of NEC files, or defective NEC files, might cause a program crash because many of EZNEC pro's cross checks aren't done when reading NEC files. If you encounter a crash when EZNEC pro
Very Large Models
Several factors should be considered when working with models of several thousand segments. The following information is provided to help you optimize the analysis of these very large models.
Calculation Time – There are two major time-consuming portions of the calculation, impedance calculation (matrix fill), and current calculation (matrix factor). The first increases as about the square of the number of segments, while the second increases approximately as the cube. So for large models, the second process dominates. Another part of the current calculation,
“solve”, can become extremely long if the model contains a large number of transmission lines. Adding ground to a free-space model will also slow calculations substantially. Specially compiled fast calculating code is used for the current calculation portion, but only if the program isn’t forced to use the disk for virtual memory. Consequently, a major speed reduction will occur if this mode becomes necessary. And it does become necessary with the largest models now possible with EZNEC pro. Calculation times of over three days have been seen with models of nearly 20,000 segments, on a 1.2 GHz
Pentium 3 machine. Effort put forth in reducing the number of segments in the model will pay off handsomely in calculation time.
Segments – In my experience of viewing models created by EZNEC pro users, many models use more segments than necessary. Calculating time is approximately proportional to the square of the number of segments for small models and to the cube of the number of segments for large models, so reducing the number of segments is always desirable. The
section contains tips for reducing segment use.
Virtual RAM Use – EZNEC pro will use the disk for virtual memory if necessary. It might be possible to gain some calculation speed by optimizing the point at which this occurs. See the
section for more information. Note that calculation speed drops very significantly when this mode is operational. See the first paragraph above. Required disk space increases as the square of the number of segments, and doubles when a double precision calculating engine is chosen. More than 10 GB is required for temporary storage for the largest models, and files of about 6 GB are written. NEC-2 engines require several times the temporary storage space as
NEC-4 engines, due to a different calculation method. EZNEC pro will check your available disk space before beginning calculations, and will refuse to run if not enough is available.
Networks – The presence of networks can slow the solution a great deal, particularly in very large models. In one model with 9000 segments, 100 networks nearly doubled the calculation time, so reduction of the number of networks can make a striking difference. One network is created for each
EZNEC User Manual current source and transmission line, and two for each “split” current source.
Combining of the networks with the main large matrix shows in the calculation progress window as “Calculating currents: Solve”. During the time this progress bar is filling, you might also see constant disk activity, particularly if the disk is being used for virtual RAM. Reducing the number of networks or the number of segments will shorten this portion of the calculation.
EZNEC/4 Considerations – EZNEC/4 was designed to be able to use an external NEC-4 calculating engine, which caused the NEC-4 calculating engines to be used somewhat differently than the NEC-2 engine. A disadvantage of this approach has shown up with very large models which include many networks. Both NEC-2 and NEC-4 engines save the main matrix in case the user wants to produce a different radiation pattern from the same model. The NEC-4 engines save the matrix before networks are combined.
So if another radiation pattern is requested when an NEC-4 engine is specified, the networks must be recombined with the matrix. In small to moderate sized models, this process doesn’t take long. But with very large models having many networks, it can take hours. The only direct solution at this time is to try and reduce the number of networks and/or segments in the model if possible. If two degree resolution is adequate, run a 3D plot for the initial calculation. Then you can choose any azimuth or elevation “slice” without recalculating. Another thing to consider is to run the model with the
NEC-2 engine. However, this engine tends to take longer to calculate large models, so there might not be an overall saving in taking this approach.
Bailing Out – You can terminate the calculations by clicking the Cancel button in the Calculation Progress Window. It might take some time to respond, so please be patient; the calculation will stop. You’ll also find that if you cover any of the EZNEC pro windows during a lengthy calculation, there might be a delay before they redraw. Both these delays are due to the fact that the calculating engine communicates with the main program only at discrete times, and updates and button responses can only be serviced at these times.
Controlling Memory Use
EZNEC pro’s calculating engine requires a large amount of memory when analyzing very large models. Before calling the calculating engine, the program checks to see how much RAM is available. If it finds an insufficient amount, it directs the calculating engine to use the computer’s disk as virtual
RAM. When this happens, calculation time is lengthened considerably. In general, fastest calculation will occur when virtual memory use is minimized or, better yet, avoided altogether. EZNEC pro gives you the ability to adjust, if you desire, the amount of RAM the calculating engine will require, which can help speed calculations in some cases. There are, however, tradeoffs involved, which will be explained below.
“Available RAM” becomes a somewhat nebulous term when dealing with
Windows operating systems, because Windows has its own virtual memory manager and provides virtual RAM as needed from a pool of the physical installed RAM and a hard disk file of up to 2 GB in size. In theory, this entire amount is available to be used as RAM. (I’ll call this “Windows RAM” to distinguish it from physical RAM.) EZNEC pro could simply pretend that 2 GB of RAM is available, and Windows would take care of swapping between the
Reference hard drive and physical RAM as needed. In practice, though, this isn’t a good idea at all when dealing with the potentially huge arrays generated by very large models. When confronted with huge blocks of data, Windows memory swapping becomes very slow. Allowing Windows to swap more than about the amount of actual physical RAM during calculation can slow calculation by an order of magnitude or more. So it’s very important for EZNEC pro not to ask for too much Windows RAM. The built-in algorithm used by EZNEC pro is conservative, and has been found to reliably avoid Windows memory swapping. However, in some circumstances you might want to push the envelope a little and have EZNEC pro ask for more Windows RAM, either to avoid going into its virtual memory mode, or to speed calculations some by reducing the amount of virtual memory it uses. There’s not usually a very large penalty for allowing EZNEC pro to use the disk for virtual RAM. A few benchmarks show a typical calculation time increase on the order of 20%, although this can vary considerably with the model, system, and amount of virtual memory being used. 20% does represent an hour of a five hour run time, though, so virtual RAM use is often worth avoiding when possible.
The size of the main array created by the calculating engine is 8N^2 bytes for the standard NEC-2 engine, where N is the number of segments. The array size is also 8N^2 for the single precision EZNEC/4 NEC-4 engine, and 16N^2 for the double precision NEC-2 and NEC-4 engines. The total amount of memory required during calculations is somewhat greater than this because of the need to also store other variables and arrays. So a single precision calculation of a 20,000 segment model requires more than 3 GB of memory.
Current systems don’t have this much installed RAM, let alone available RAM, so virtual memory use is unavoidable with this size model. But you might be able to decrease the amount of virtual memory that’s created by EZNEC pro and decrease the calculation time slightly. For smaller models, you can modify the threshold at which EZNEC pro switches to virtual memory use. However, if you set the threshold too high, you run the risk of having Windows do an excessive amount of memory swapping, which will greatly slow calculations.
If you choose to manually adjust the amount of Windows RAM which will be used by the calculating engine, make the adjustment, then watch during calculation for excessive or constant disk use which might indicate excessive
Windows disk swapping. If it occurs, reduce the amount. Note: Heavy disk activity is normal during some parts of the calculation, most notably during the
“Solve” portion of the current calculation. It’s not uncommon to see virtually constant disk activity during this period. When virtual memory is being used, you’ll also see heavy activity during the “Processing Data Saved to Disk” operation, and for short periods several times during the impedance and current calculations.
There’s one other important thing you should keep in mind. EZNEC pro never uses more memory than the model requires, so all you can adjust is the
maximum amount it can use. If your model requires less than the maximum, any adjustment you make to increase the maximum will have no effect. (Of course, if you reduce the amount EZNEC pro can use, it could result in virtual memory use where it wouldn’t have occurred without the adjustment.) If your model doesn’t require virtual memory (which is indicated in the calculation progress window), increasing the maximum amount of Windows RAM EZNEC
pro can use will have no effect.
EZNEC User Manual
The maximum amount of Windows RAM used by EZNEC pro is adjusted by entering the following lines in the [Special Options] section of the EZNEC.INI file. Each parameter overrides the one shown below it in this list; that is, a parameter will be ignored if one above it in this list has been specified. (The order of items in the EZNEC.INI file makes no difference.)
MaxAbsRAMUsedK = #
Sets the maximum amount of Windows RAM used, where # is the amount in kbytes.
MaxAbsRAMUsedPct = #
Sets the maximum amount of Windows RAM used, where # is the percentage of installed physical RAM.
MaxQualRAMUsedPct = #
Sets percentage used in the standard maximum memory use calculation, as follows: max Windows RAM = max((#/100)*(installed RAM), act avail RAM)).
This has the same effect as MaxAbsRAMUsedPct, except that if more physical RAM is available than the specified percentage of installed
RAM, the memory use will be set to the amount of available physical
RAM. This is the default EZNEC pro method of determining maximum
Windows RAM use, with a default percentage of 50.
Unlike many of the EZNEC.INI file options, it’s not necessary to exit and restart EZNEC pro after changing one of these parameters; they will take effect immediately. You can see the approximate amount of Windows RAM which will be used by the calculating engine for a given model by selecting
Memory Info from the Control Center Utilities menu.
Using An External NEC-4 Engine (EZNEC/4 Only)
This section applies only to EZNEC/4.
For a number of reasons, discontinuation of support for external NEC-4 engines is being considered for future versions. Comments are welcome, particularly from anyone who is using this feature or anticipates using it in the future. Please send any comments to [email protected]
EZNEC/4 is designed so that it can be used with a user-supplied NEC-4 program. This may be useful in comparing results from several variations of
NEC-4, or in doing specialized calculations with a customized program.
However, because of the possibility of code modifications and the variety of different compilers available, EZNEC/4 might not work properly with some variations. Please read the following information before using an external
NEC-4 program with EZNEC/4.
Running EZNEC/4 with an external NEC-4 program
Before running an external NEC-4 program, it’s first necessary to create a batch file to specify the input and output file names. Do this as follows.
Create the batch file, which is a text file containing the following line:
MyNEC4.exe <IOF.txt where MyNEC4.exe is the name of the executable NEC-4 program to be run, and IOF.txt is another text file which contains:
Give the batch file the name of the executable file but with a BAT extension
(MyNEC4.BAT for the example), and put it and the IOF.txt file in the same directory as the NEC-4 program executable file.
When you first run the external NEC-4 program, you have to specify the program name via the
Engine/External NEC-4 Program selection. Specify the name of the batch file, not the executable file, when prompted. The external NEC-4 program can be in any directory. Input and output files will be created in its directory. You can make the external program the default engine if desired by selecting Save As
Defaults in the Control Center Options menu after specifying the NEC-4 engine. To choose a different external NEC-4 program, simply click the
Control Center Options/Calculating Engine/External NEC-4 selection to open a file selection dialog box. You must of course create a batch file for each calculating engine. They can share an IOF.txt file if all batch files are in the same directory, or if the IOF.txt path is specified in the batch files.
Tips for Running DOS Programs
Normally, calling a DOS program will result in opening a DOS window when the external NEC-4 program starts. This window will remain open after the external NEC-4 program ends. This is generally preferred, since it allows you to see any error messages that were generated by the external program and sent to the normal DOS screen output. However, when running a frequency or
SWR sweep, it’s desirable to have the window close after the external program is finished. The external program is called once for each frequency step, requiring the window to be closed after each step. The window can be made to close automatically after the program finishes by creating a DOS program information file (PIF). To create the file,
In Windows Explorer, right-click the batch file created in the above section.
Click Properties, then Create Shortcut. The new shortcut will appear at the end of the list of files.
Right-click the shortcut and select Properties.
Click the Program tab at the top.
Click the Close on Exit box to make it checked. Click Ok.
Right-click the shortcut again, and select Rename.
Delete the “Shortcut to”, and the extension. That is, if the original name was “Shortcut to MyNEC4.bat”, change it to “MyNEC4”. Then click Ok.
When specifying an external NEC-4 program in EZNEC/4, enter the batch file name as before. The PIF will be used automatically.
The window auto-close feature can be disabled in the future by simply right-clicking the shortcut file in Windows Explorer, choosing Properties then the Program tab, and unchecking the Close on Exit box.
EZNEC User Manual
Most EZNEC/4 features are available when using an external NEC-4 program. However, EZNEC/4 isn't able to take advantage of its ability to save and re-use ground files. This is because different compilers store files in different formats, and EZNEC/4 has no way of knowing which compiler was used for the external program. When using an external program you also lose indications of calculation progress and whether out-of-core memory is being used, and the ability to terminate execution before it’s complete.
EZNEC/4 can't tell the maximum array dimensions for an external program, so the user has to take the responsibility of making sure the number of description wires, segments, connections, etc. don't exceed the NEC-4 array dimensions.
EZNEC/4 depends on certain characteristics of the output file to identify the data it needs. Modification to the data format in the NEC-4 output file may cause improper operation of EZNEC/4. In general, additional outputs will be ignored by EZNEC/4 and won't cause a problem.
One compiler which generates programs causing problems with EZNEC/4 is the Microsoft FORTRAN PowerStation version 1.00. A revision of this compiler, version 1.0a, seems to produce acceptable programs. The sign-on screen for the compiler may indicate version 1.00 even though it has been updated to 1.0a. Following are a few of the files from both versions, listed to help you identify which you may have. All these files are in the \F32\BIN directory:
File v. 1.00 v.1.0a
BINDMSF.EXE 73,206 01-30-93 64,302 01-15-94
F23232.EXE 404,480 02-08-93 489,984 12-22-93
LINK32.EXE 277,504 02-03-93 52,224 02-02-94
LINK.EXE ABSENT 385,536 01-19-94
Microsoft PowerStation v. 1.00 has bugs which result in errors when implicitly converting to a complex variable type, or between complex types. At least one instance of the former is known to exist in the standard NEC-4.1 code, and it is likely that others are also contained in the code. The known instance causes NEC-4.1 to crash under some circumstances, so was relatively easy to find. Others may simply cause incorrect results. EZNEC/4 may exercise features of NEC-4.1 which you wouldn't ordinarily use, causing crashes or inaccuracies when using an NEC-4.1 program which is thought to be working properly. Do not use Microsoft PowerStation v. 1.00-compiled programs with
NEC-4.1 Medium Height Bug
When using an external NEC-4 program and a model with two ground media, the second medium won't be interpreted correctly unless a special option is entered. This is due to a bug in NEC-4.1 which inverts the sign of the medium height parameter (CHT) on the GD "card". EZNEC pro calculating engines
EZCalc4 and EZCalc4D have been modified to interpret the parameters as defined in the NEC-4.1 manual, which is the same interpretation used by
NEC-2. EZNEC/4 will normally write the NEC input file with this convention.
However, you can force EZNEC/4 to write the GD "card" with an inverted sign
Reference for the CHT parameter under some circumstances. This is done by setting a special option in the EZNEC.INI file, as follows:
EZIHS = # where # = 1 => Invert sign when using external NEC-4 program
# = 2 => Invert sign when saving file in NEC format
# = 3 => Invert sign when either of the above
If you want to modify your NEC-4.1 program source code to remove the bug, it can be done by inverting the value of variable CLIFH. I suggest inverting it in subroutine REFPT1 where it calls REFPT, to keep the meaning of the variables similar to their use in NEC-2:
EZNEC pro is not designed to operate with an external NEC-2 or NEC-3 program.
Double Precision Operation
EZNEC-M and EZNEC/4 include a double-precision NEC-2 calculating engine in addition to the standard mixed-precision engine. EZNEC/4 also includes a double-precision NEC-4 calculating engine (EZCalc4D) as well as the standard single-precision EZCalc4 engine. Also, user-supplied doubleprecision NEC-4 programs can be used with EZNEC/4. The choice of calculating engine type affects the size of model at which virtual memory operation will take place; it will happen with a smaller number of segments
(approximately 0.7 times as many) when running double-precision calculations than when running single precision. In addition to the inherent slowing during virtual memory operation, operation may also be slowed somewhat because of the increased sizes of arrays which must be written to and read from the disk during calculation. Approximately twice as much memory and temporary disk space will be used for double precision operation.
The maximum number of segments and wires which EZNEC/4 will accommodate is the same for both single and double precision.
The interface portion of the program is always single precision. Consequently, wire coordinates, for example, are passed along to the calculating engine as single-precision numbers, and single-precision arithmetic is used to determine wire connections within the interface. Also, functions done by the interface such as wire rotation and replication are done in single precision. Marginal conditions of wire connection (where wire ends are not the same but are very close to 0.001 segment apart) should be avoided. Both EZNEC and the calculating engine modify coordinates slightly to force a match when wire ends are extremely close, but it could be possible for one to force or assume a connection and the other not, under marginal conditions. So while unlikely, this situation should be avoided. When using an NEC-4 engine (EZNEC/4 only), the output of the interface portion of the program is an NEC-4 input file which is passed to the calculating engine. The precision of all NEC-4 calculations is determined by the calculating engine choice.
for additional information about using a double-precision NEC-4 program with EZNEC/4.
EZNEC User Manual
Norton Antivirus – When background virus checking is enabled, Norton
Antivirus has been found to cause the EZNEC installation program to hang.
Antivirus and Anti-malware (-adware or -spyware) Programs – When set to constantly check for “virus-like” activity, some programs cause a very significant slowing of the calculations. It appears to be due to interception and analysis of the messages sent from the calculating engine to the main program in order to show calculation progress. Slowing in terms of a fraction of total calculation time will be greatest for simple models, since this is when the time spent sending calculation progress messages is the greatest fraction of total calculation time. Total slowing will be most noticeable when doing a frequency or SWR sweep of a relatively simple model. If the slowing is objectionable, it can be alleviated either by turning off the feature in the antivirus or anti-malware program, or by directing EZNEC to update the calculation progress display less frequently. The latter is done by setting
CalcProgReduction. More detail is included for particular programs below.
McAfee Antivirus – When background virus checking is enabled, some versions of McAfee Antivirus cause EZNEC calculations to proceed extremely slowly, to the point that the mouse cursor might be unresponsive or jerky during EZNEC calculations. So far, this has been seen only in McAfee
Antivirus v. 4 with some program updates. See the Antivirus and Anti-malware
Programs section above for solutions.
ZoneAlarm – ZoneAlarm v. 6.1.744.001 was found to slow EZNEC calculations but not nearly to the degree caused by the McAfee program.
Slowing was found to occur only when the ZoneAlarm “OSFirewall” feature is on. This feature is normally enabled whenever the ZoneAlarm Program
Control Level is set to Medium or High, but it can be separately disabled by unchecking it in ZoneAlarm’s Program Control/Main/Custom window.
Alternatively, the slowing can be reduced by using the EZNEC Special Option mentioned in the Antivirus and Anti-malware Programs section above.
Matrox PowerDesk - Has been reported to prevent EZNEC from remembering window positions correctly so that windows re-open in different positions than when they close. To prevent this problem, uncheck the box labeled "Save/Restore window positions when programs are opened/closed" in the PowerDesk/QuickDesk Multi-Display Controls dialog box.
Window Washer – For reasons which are baffling, Window Washer – some versions at least -- gives the user the ability to cause automatic deletion of files in the Windows temporary file directory at periodic intervals, for example every hour. EZNEC, and many other programs, routinely write temporary files into that directory. These temporary files are written with the expectation that they can be read at some later time (but before the program ends). If a temporary file written by EZNEC has been deleted, EZNEC will crash when it attempts to read the missing file. EZNEC is, of course, only one of many applications which will react this way. Temporary files should not be deleted except just after turning a computer on or rebooting, or just before turning it off or rebooting.
The Calculation Progress Window
The Calculation Progress Window appears whenever EZNEC calls the calculating engine to do calculations. It remains on the screen until calculations are finished, and no other EZNEC operations can occur while it’s being displayed. It shows several important pieces of information, plus it allows you to terminate calculations before they finish. [EZNEC/4 only]: This window doesn’t appear if you’re using an external (user-supplied) NEC-4 program for calculation.
Calculating Engine Type -- The title bar shows which calculating engine is being used. For the standard EZNEC program it will always show NEC-2.
With the other programs, it will show which of the available calculating engine options is being used.
Frequency – The frequency is shown just below the title bar. This is particularly useful when doing a frequency sweep.
Stepped Diameter Correction – This message appears under the frequency if one or more groups of wires is being corrected with the stepped diameter correction feature. Its appearance doesn’t guarantee, however, that all elements of a Yagi, for example, are being corrected. To determine this, you
. [EZNEC/4 only]:
Stepped Diameter Correction will normally be disabled when using an NEC-4 calculating engine, so this message won’t appear in that case.
Disk Use As Virtual RAM – If the calculating engine can’t find enough available RAM, it uses the disk as virtual RAM. Although Windows will do this on its own, the routines built into NEC are much more efficient for the purposes of doing the necessary calculations. You won’t see this message with the standard EZNEC program due to its segment limitation, and only with large models when running other EZNEC programs.
Calculation Progress – Several progress bars appear in the window as the calculation runs. Which bars appear is determined by the calculations being done. A ground file calculation bar appears only when using Real, High
Accuracy ground, and then only if EZNEC failed to find a file containing suitable data from a previous calculation. Progress as shown on the bars doesn’t necessarily proceed at a constant rate, so you shouldn’t be concerned if it seems to speed up, slow down, or occasionally pause as calculations proceed. In EZNEC pro programs, the current calculation is split into two parts, “Factor” and “Solve”, if any current sources or transmission lines are present in the model. The “solve” portion tracks the progress of combining the main matrix with networks, which can take considerable time with very large models. (See
.) You’ll also see a “Geometry Check” bar showing the progress of EZNEC’s geometry check.
Cancel – Clicking this button will stop calculations and return you to the interface part of the program. To avoid unnecessarily slowing calculations, the state of this key is tested only periodically, so there might be a delay before the program responds to your cancellation request, particularly in models containing a very large number of segments.
The Lastz.txt file is created when a
is run. It contains, in comma-delimited ASCII format, the impedance and SWR at each source and frequency. It remains in the EZNEC program directory after the
EZNEC User Manual program ends and can be used for other purposes if desired. Text headers in the first line identify the field contents.
Except when EZNEC is writing to the file, its read-only attribute is set. EZNEC depends, for proper operation, on the contents of this file to be correct and in a particular format, so Lastz.txt shouldn’t be edited under any circumstances.
If a modified version is necessary, make a copy having a different name and edit the copy. Some applications used for viewing Lastz.txt, such as spreadsheets, may lock the file and make it inaccessible to EZNEC. If the file is locked when EZNEC requires access, you’ll get an error message, and will be required to release the file by closing it in the locking application before
EZNEC can proceed.
A few choices are likely to be so seldom used that they don’t justify being put into a menu. However, EZNEC still provides a way to enable or change these choices. In the EZNEC program directory is a file named EZNEC.INI. EZNEC reads this file each time it starts, so it can be used to communicate the values of special options.
The EZNEC.INI file can be edited with any text editor. Or you can conveniently open it for editing with the EZNEC Editor by choosing Edit .INI
File in the Control Center Utilities menu. Once edited, save and close the file, then end the EZNEC program. Wait for a few seconds for the disk cache to dump, then restart EZNEC. The new changes should then be in effect.
All entries are case insensitive. Spaces around the = sign are optional. All entries are put into the file in the [Special Options] section; that is, they go below that heading.
DotMult = # where # is a number from 0.5 to 5: Increases or decreases the size of the grid dots on the 2D Display grid. It modifies the value of the line width selected by the Control Center Options/Plot Printing/Printed Plot Line
Width option, only when printing grid dots. This affects only the 2D printed plot. See PrintedOffsetAxisWidth below.
PrintedOffsetAxisWidth = Fixed Lines can be shown as broken only when the line width is one. There are three situations where broken lines are displayed: in the View Antenna display, the axes when the display is offset from the origin, and current phase markers; and in the 2D display when showing separate plot polarizations. When printing, EZNEC will normally print these lines with the same width as other lines, so if the
will be printed as solid. Setting the PrintedOffsetAxisWidth option will force the line width of broken lines to one when printing, so they will be printed as broken. They might, however, be undesirably narrow on some printers as a result.
PrinterMargin = # where # is a number from 0 to 3, or a number followed by the letter “c” (either case) from 0c to about 7.6c: Sets the width of the margins around printed graphics plots (2D, 3D, SWR, and View Antenna displays). If the number is followed by c, the number is interpreted as being in cm; otherwise, in inches. For example, 1.2 will produce margins of 1.2 inches;
2.3c will produce margins of 2.3 cm.
CursorBorder = None Turns off the outline around the outer border of the cursor in the 2D, 3D, and SWR plots. This is to avoid a problem seen in
Windows 2000 with the ATI Xtra 128 video board where the cursor border is the same color as the cursor, and gets left behind when the cursor is moved.
PrDataLineSp = # where # is a number from 1 to 2. This sets the line spacing for data from a Data Window printed under a plot. It affects only printed output.
CalcProgReduction = # where # is a number from 0 to 3; other values ignored. Use when the program is slowed by an anti-virus or anti-malware
.) Limits how often the calculation progress indicator is updated during calculation. A value of zero results in normal operation. Higher values (up to 3) reduce the update frequency, speeding operation but making the calculation progress indication less smooth.
MaxCMWidth = # where # is an integer. EZNEC pro only. EZNEC pro saves
Antenna Notes as CM “cards” in the NEC input file. This sets the maximum width of these lines, in number of characters.
NECRadials = On Standard EZNEC only: See
for use of this option.
WireInfoDist = # where # is an integer from –1 to 20. If the value is zero or positive, it defines the distance within which the cursor has to be before the
popup window appears. If the value is –1, the popup window will appear only when the right mouse button is clicked while holding down the
ButtonFontSize = # where # is a number. This sets the font size for the
, and is included because some users have reported that the text doesn’t fit when EZNEC is run at some resolutions on some systems. The default font size is 8, so I suggest you try a size slightly smaller than this if you experience this problem. I recommend setting the
ButtonFontName to Arial if you use this option. Arial permits setting font size to any value, including fractional values. The default font MS Sans Serif allows only whole, even point sizes.
ButtonFontName = fontname where fontname is the name of a valid font, such as Arial. This sets the font type for the Control Center Action Buttons.
Please see ButtonFontSize, above.
MaxMSFreqs = # where # is either 8 or 100. MicroSmith versions 2.000B and earlier are able to accommodate a maximum of 8 frequency sweep steps in the .DAT file (for frequency dependent impedances). Later versions can accommodate up to 100. EZNEC will write a maximum of 8 or 100 depending on an internal setting. The normal default value is 100, but a value of 8 can result from importing values from a DOS EZNEC configuration file
(ELNEC.CFG). The first time you run EZNEC with this option present in the
EZNEC.INI file, its value will become the permanent maximum value. After that, you can remove this line from the EZNEC.INI file if desired. The only ways it can be changed except by using this entry in the EZNEC.INI file are by uninstalling and reinstalling EZNEC (in which case it’ll be set to 100) or by importing data from an ELNEC.CFG file by means of the EZNEC Installation
EZNEC pro only:
LD5Translation = Off inhibits translation of LD5 (wire loss) cards in NEC description file. See
about LD “card” translation.
EZNEC User Manual
LD5Translation = First will cause EZNEC pro to apply the wire loss parameters of the first LD5 “card” read as global Wire Loss, and ignore additional LD5 “cards”.
The following three options are used for controlling Windows RAM use when
for more information.
MaxAbsRAMUsedK = #
MaxAbsRAMUsedPct = #
MaxQualRAMUsedPct = #
OpenPF Plot File Format
EZNEC saves 2D and 3D plot (trace) files using the OpenPF standard. Files using this standard are commonly given the extension .PF, and EZNEC uses this for ordinary 2D plot files. However, plots generated by the frequency sweep are given extension .P #, where # represents the frequency step. 3D plot files are given the extension .PF3. All these conform to the following standard. The standard is included here for those who want to develop compatible software or who have a need to directly read the data in these files.
Important Note: Although the plot files written by EZNEC conform to the
OpenPF standard, and EZNEC is able to read some 2D plot files produced by users or other programs, EZNEC isn’t generally able to import or correctly read OpenPF files created by users or other programs.
OpenPF Plot File Standard Version 1.0 June 1, 1995
The following standard was developed by Brian Beezley and Roy Lewallen as a common format for sharing data files between programs. Although we both contributed to the content, the original proposal was Brian
=s, and he is the author of the following standard and did the majority of the work. We encourage others to adopt this standard.
OpenPF is an open, nonproprietary standard for computer files that contain electromagnetic field data. OpenPF is intended for files created by antenna analysis programs and for files containing measurements. OpenPF files can be used to archive or transport data. Programs can use the files to plot fields and radiation patterns on a screen, printer, or plotter.
The OpenPF file format is extensible. Data is organized into blocks that begin with a block type identifier followed by block length. This structure allows a file parser to skip and ignore blocks it's not designed to handle, including block types defined in future revisions of OpenPF.
The blocks defined below provide for 2 D relative far field data (azimuth and elevation radiation patterns) and 3 D absolute near and far field data. 3 D radiation patterns can be represented by a set of 2 D data blocks.
The file format enables a single file to contain near and far field data, absolute and relative data, azimuth and elevation data, low and high resolution data, partial and full data cuts, data for multiple frequencies, and unidentified data.
The file format provides for new fields in future OpenPF revisions without the overhead of reserved bytes. New fields can be appended to any file block.
File parsers that use block length to advance to the next block will skip over new fields.
OpenPF uses standard coordinate systems. For rectangular coordinates, X and Y are in the horizontal plane and Z is height. For spherical coordinates, R is radial distance, phi is azimuth angle, and theta is zenith angle. For cylindrical coordinates, rho is horizontal distance, phi is azimuth angle, and z is height. Azimuth angle is 0 along the X axis and increases in the XY plane toward the Y axis (counterclockwise). Zenith angle is 0 along the Z axis and increases in the Z phi plane toward the phi ray. Units are meters and degrees.
OpenPF files use the Intel processor "little endian" data convention (least significant byte first for multibyte data). Bit number 0 is the least significant bit.
Bits marked as reserved are undefined and should not be assumed to be 0.
OpenPF files use the file extension ".PF".
In the descriptions that follow, word means a 16 bit unsigned integer and FP means a 32 bit, single precision, floating point number that conforms to the
IEEE 754 1985 standard. ASCII means a character string that uses the extended ASCII PC 8 symbol set.
OpenPF files begin with a block of the following format:
Header length word
Source length byte
Title length byte
Environment length byte
Notes length word
This byte identifies the OpenPF version used to generate the file. The version number consists of a major revision (an integer) and a minor revision (an integer between 0 and 9) separated by a decimal point. The upper nibble (4 bits) contains the major revision and the lower nibble the minor.
This field is the total length of the header in bytes. File parsers should use this length to advance past the header instead of assuming that data blocks begin immediately after the notes string. Future OpenPF revisions may define additional fields after the notes string. Header lengths less than 3 are invalid.
Source, Title, Environment, and Notes Lengths
These fields specify the lengths in bytes of the ASCII strings. Zero is valid.
This string identifies the data source. This may be an antenna analysis program, an antenna test range, a laboratory, etc. No bytes are allocated for a zero length string.
Title, Environment, and Notes Strings
EZNEC User Manual
The title string describes the antenna. The environment string describes the antenna environment (free space, antenna height, ground constants, etc.).
The notes string contains auxiliary information that might be displayed only upon request. Data blocks that follow may contain strings that override these global strings. No bytes are allocated for zero length strings.
Data following the header is organized into blocks. Each data block begins with block type (a byte) followed by block length (a word). Block types 0 through 127 are standard and reserved. Programs may use types 128 through
255 for special purposes, but block length must always follow block type so that file parsers can skip over the block. Blocks may appear in any order. The following standard blocks are defined:
Block type byte (0)
Block length word
Rest of block
Block type 0 is a no operation block. Its purpose is to provide a standard ignore me block. Normally this block isn't used, but it may be convenient when patching a file. Block length is the total length of the block in bytes. Block lengths less than 3 are invalid.
Relative Far Field Blocks
Block type byte (1 16)
Block length word
Title length byte
Environment length byte
Notes length word
Plane angle FP
Number of points word
First angle FP
Angular increment FP
Data points each FP
Block types 1 16 contain planar cuts of relative far field data as follows:
Block Data Units
1 Total magnitude dBi
2 Horizontal magnitude dBi
3 Vertical magnitude dBi
4 Right circular magnitude dBic
5 Left circular magnitude dBic
6 Major axis magnitude dBi
7 Minor axis magnitude dBi
8 Ellipticity dB
9 Total phase degrees
10 Horizontal phase degrees
11 Vertical phase degrees
12 Right circular phase degrees
13 Left circular phase degrees
14 Major axis phase degrees
15 Minor axis phase degrees
16 Polarization tilt degrees
Ellipticity is the length of the minor axis of the polarization ellipse divided by the length of the major axis expressed in dB (the IEEE 754 1985 floating point code for infinity is valid). Polarization tilt is the counterclockwise angle between the major axis and the E(theta) direction.
This field is the total length of the block in bytes. Block lengths less than 3 are invalid.
Title, Environment, and Notes Lengths
These fields specify the lengths of the ASCII strings in bytes. Zero is valid.
Frequency is in MHz.
This byte is 0 for azimuth data (constant zenith angle) and 1 for elevation data
(constant azimuth angle). Other values are reserved.
This field is the zenith angle for azimuth data and the azimuth angle for elevation data.
The bits of this byte have the following meaning when set:
Bit Azimuth Data Elevation Data
0 X symmetry XY symmetry
1 Y symmetry Z symmetry
Symmetry means that the data has the same value when reflected about the line or plane indicated. For azimuth data, bits 0 and 1 refer to the X and Y axes. For elevation data, they refer to the XY plane and the Z axis. Both bits may be set simultaneously. Bits 2 7 are reserved.
Number of Points
This field is the number of data points that follow. 0 is valid.
This field is the angle of the first data point.
This field defines the sign and magnitude of the angular difference between successive data points.
EZNEC User Manual
The data set begins at the first angle. The angles of successive data samples differ by the angular increment.
Title, Environment, and Notes Strings
When string length is nonzero, the string overrides the corresponding header string for this block. When zero, the header string applies for this block and no string space is allocated.
Absolute Near and Far Field Blocks
Block type byte (64 81 & 96 101)
Block length word
Title length byte
Environment length byte
Notes length word
Coordinate system byte
Number of A points word
First A FP
A increment FP
Number of B points word
First B FP
B increment FP
Number of C points word
First C FP
C increment FP
Data points each FP
Block types 64 81 contain absolute fields. Block types 67 81 are field components resolved in rectangular coordinates. These blocks are defined as follows:
Block Data Units
64 Power density watts/square meter
65 Peak E magnitude volts/meter
66 Peak H magnitude amps/meter
67 Px Poynting vector watts/square meter
68 Py Poynting vector watts/square meter
69 Pz Poynting vector watts/square meter
70 Ex magnitude volts/meter
71 Ey magnitude volts/meter
72 Ez magnitude volts/meter
73 Hx magnitude amps/meter
74 Hy magnitude amps/meter
75 Hz magnitude amps/meter
76 Ex phase degrees
77 Ey phase degrees
78 Ez phase degrees
79 Hx phase degrees
80 Hy phase degrees
81 Hz phase degrees
Block types 96 101 contain absolute electric field components resolved in spherical coordinates as follows:
Block Data Units
96 E(R) magnitude volts/meter
97 E(phi) magnitude volts/meter
98 E(theta) magnitude volts/meter
99 E(R) phase degrees
100 E(phi) phase degrees
101 E(theta) phase degrees
Use block type 65 for peak E magnitude.
Block Length, String Lengths, and Frequency
These fields are the same as for relative far field blocks.
This field is antenna input power in watts.
This byte specifies the coordinate system used to locate data points (it does not specify the coordinate system used to resolve field components). The byte is 0 for rectangular coordinates, 1 for spherical coordinates, and 2 for cylindrical coordinates. Other values are reserved. Coordinates are defined as follows:
Coordinate System A B C
0 Rectangular X Y Z
1 Spherical R phi theta
2 Cylindrical rho phi z
The low order bits of this byte have the following meaning when set:
0 A coordinate symmetry
1 B coordinate symmetry
2 C coordinate symmetry
Here, symmetry means that the data has the same value when the coordinate is negated (this definition is not the same as that for relative fields). Any of the bits may be set simultaneously. Bits 3 7 are reserved.
Number of A, B, or C points
These fields specify the number of points for each coordinate. 0 is invalid. The total number of data points is the product of A, B, and C. For rectangular coordinates, the field is computed over a point, line, rectangular surface, or rectangular volume. For spherical coordinates, the field is computed over a point, line, circle, disc, spherical surface, spheroid, or portion thereof. For
EZNEC User Manual cylindrical coordinates, the field is computed over a point, line, circle, disc, cylindrical surface, cylindrical volume, or portion thereof.
First A, B, and C
These fields specify the starting values of each coordinate.
A, B, and C Increments
These fields define the sign and magnitude of the difference between successive coordinate values.
Points are ordered as follows: A cycles from first to last, then B, and finally C.
The coordinate values of successive data samples differ by the A, B, or C increments.
Title, Environment, and Notes Strings
These fields are the same as for relative far field blocks.
Smith Chart Programs
MicroSmith, by Wes Hayward, W7ZOI is a DOS-based program which allows you to view impedances on a Smith chart. With its aid, impedance matching networks can be designed. EZNEC is able, in its
mode, to write files for direct input of source impedance data to MicroSmith. MicroSmith was published by the
American Radio Relay League, but is no longer available. I suggest winSMITH as a currently available substitute. Note: MicroSmith v.
2.000B and earlier permit no more than 8 frequency steps in a .DAT file
(for frequency dependent loads), while later versions allow 100.
EZNEC can be set to limit the number of MicroSmith .DAT file steps to either 8 or 100. See the MaxMSFreqs option in
for information about how to set this limit.
winSMITH is no longer available. I am currently looking for a suitable replacement.
Input File Formats
Frequency Sweep Input File
The frequency sweep input file contains a list of frequencies to be used for the frequency sweep. Its name is specified in the Control Center Setups menu,
Frequency Sweep selection.
Frequencies are in megahertz (MHz), and consist only of numbers. They may be in any order and do not have to be equally spaced. (They will be sorted in increasing order for display.)
Frequencies must be separated by spaces, carriage returns, or a combination of these. If your regional decimal separator is a period (.) and not a comma (,), a comma may also be used as a separator, alone or in combination with spaces or carriage returns.
Any line not beginning with a number is considered to be a comment, and ignored. They may be entered anywhere in the list.
Entries of zero, or empty fields, are ignored.
A negative entry will terminate reading of the file, so that only values preceding the negative entry will be used. This is a convenient way to limit processing to only the first part of a lengthy list.
Wire Coordinate File
The wire coordinate file is used for importing wire coordinates via the Wires
Window or the Control Center, by choosing Import Wire Coordinates from
ASCII File in the File menu.
The plus and pro program types permit two different file formats; the standard type permits only the first one described below.
LL PROGRAM TYPES
The ASCII import file consists of an optional line defining the units to be used for coordinates and diameter, followed by one line per wire giving the end coordinates, diameter, and, optionally, number of segments. Comments may appear anywhere in the file. Tabs, spaces, commas, or any combination may be used as delimiters.
The optional units specification is done on one line and must precede all wire definitions. If absent, wire coordinates and diameters are assumed to be in meters.
Wire definitions consist of end 1 coordinates, end 2 coordinates, and diameter. If desired, the number of segments can be added as an eighth field.
If the segment field isn't included, the wire will be automatically segmented using the "conservative" criterion.
The file is case-insensitive. Blank lines, and any text on a line following a semicolon will be ignored. Blanks, tabs, or any combination can be used as delimiters (separators between fields or individual specifications). Commas
can be used as delimiters only if your decimal separator is not a comma.
Number format must correspond to your Windows regional setting. That is, if you normally write one-and-one-half ‘1,5’, then it must be written
that way in this file.
Imported wires can be used to add to or replace an existing definition.
Example 1 (for the U.S. and other regions having a period as the decimal separator):
This is the wire configuration for the 4-square array of example description file
4SQUARE.EZ. Note that a complete antenna description must also include sources, which must be added from within EZNEC pro.
; Example file for EZNEC wire importing: four square array.
; ONLY FOR REGIONS WITH PERIOD DECIMAL SEPARATOR.
; NOTE that wire import files don't contain sources or information other than wires.
; To actually make a 4-square array with the information from this file
; requires specification of sources, frequency, ground type, etc.
; The first non-comment line is the units specifier. This will cause:
; -- Program UNITS to be changed to FEET
; -- Wire coordinates to be interpreted as being in feet
EZNEC User Manual
; -- Wire diameter to be interpreted as being in inches ft in
; Next are the wire specifiers. Spaces, commas, and tabs are used in this example
; as delimiters to illustrate the flexibility available. As this file is written, these
; wires will be automatically segmented using "conservative"
; density. If desired, an additional field could be added to any line to cause
; "minimum" recommended density, or a specific number of segments.
; The first three numbers are the end 1 coordinates (in feet because of
; the first unit specifier above). The next three are the end 2 coordinates
; (ft). The seventh number is the diameter (in inches because of the
; second unit specifier).
0,0,0 0 0 32.75 1.5
0 34.42 0 0 34.42 32.75 1.5
34.42, 0 0 34.42 0 32.75, 1.5
34.42 34.42 0 34.42,34.42 32.75 1.5
; Normally the wire specifications would be written to be easier to read.
; The above format was chosen to illustrate the flexibility available in
; choosing field delimiters.
Example 2 (for regions having a comma as the decimal separator):
This is the wire configuration for the 4-square array of example description file
4SQUARE.EZ. Note that a complete antenna description must also include sources, which must be added from within EZNEC.
; Example file for EZNEC wire importing: four square array.
; ONLY FOR REGIONS WITH COMMA DECIMAL SEPARATOR.
; NOTE that wire import files don't contain sources or information other than wires.
; To actually make a 4-square array with the information from this file
; requires specification of sources, frequency, ground type, etc.
; The first non-comment line is the units specifier. This will cause:
; -- Program UNITS to be changed to METERS
; -- Wire coordinates to be interpreted as being in meters
; -- Wire diameter to be interpreted as being in millimeters m mm
; Next are the wire specifiers. Only spaces or tabs are used in this example
; as delimiters to separate fields. Commas are not allowed as field delimiters
; in regions where a comma is used as the decimal separator. As this
; file is written, these wires will be automatically segmented using
; density. If desired, an additional field could be added to any line to cause
; "minimum" recommended density, or a specific number of segments.
; The first three numbers are the end 1 coordinates (in meters because of
; the first unit specifier above). The next three are the end 2 coordinates
; (meters). The seventh number is the diameter (in mm because of the
; second unit specifier).
0 0 0 0 0 9,9822 38,1
0 10,4912 0 0 10,4912 9,9822 38,1
10,4912 0 0 10,4912 0 9,9822 38,1
10,4912 10,4912 0 10,4912 10,4912 9,9822 38,1
; Normally the wire specifications would be written to be easier to read.
; The above format was chosen to illustrate the flexibility available in
; choosing field delimiters.
Complete Rules for Wire Files Used for Importing with the first format
No distinction is made between upper and lower case letters.
A semicolon (;) and anything to its right on a line will be ignored.
Blank lines will be ignored.
Spaces, tabs, or combination may be used as delimiters. Commas may be used in regions (such as the U.S.) where a comma is not the decimal separator.
There are two types of specifications: wires and (optional) units.
Units specification line (optional) must precede all wire specifications.
Text fields (only) can be surrounded by quotation marks (" "). These are coordinate units, diameter units, wire diameter specified as wire gauge, and
"M" specifying minimum segmentation. Quotation marks are not required for any field.
The user will be given the choice of adding the wires to the existing description or replacing the existing description with the wires.
Zero, one or two unit specifiers may be included.
Unit specifiers must precede all wire specifications.
If two specifiers are given, they must appear on the same line and be separated by a valid delimiter.
The first unit specifier is the coordinate unit specification. It will modify the
EZNEC UNITS selection, and wire coordinates in the import file will be interpreted as being in the specified units. If the units specifier line is absent, all coordinates and diameters will be interpreted as being in meters.
The second unit specifier (optional) is the diameter specification. Wire diameters will be interpreted as being in these units. The units used by the program for wire diameter may be different than, and will not be determined or changed by, this specification. (For example, if both the coordinate and diameter units specifications are feet, EZNEC will change its UNITS to feet. If a diameter is given in the import file as 0.5, it will be interpreted by EZNEC as having a diameter of 0.5 feet. However, EZNEC shows diameters in inches when UNITS are feet, so after importing, the wire will show up in EZNEC as having a diameter of 6 inches.) If no diameter unit specifier is given, wire diameters will be interpreted as being in the same units as the end coordinates.
Only the first two letters of each specifier is read. They are interpreted as follows:
M or ME - meters (If M is used alone, it must not be followed by any other character, including a period.)
MI or MM - millimeters
FT or FE - feet
IN - inches
WA or WL- wavelengths
EZNEC User Manual
Wire specifications must have at least 7 fields.
Fields are end 1 x, y, z coordinates; end 2 x, y, z coordinates; diameter; and, optionally in an eighth field, number of segments. See below for more information about the segment field. Wires having zero length or diameter will be rejected. Coordinates are interpreted as being in the units specified by the first unit specifier. If no unit specifiers are given, they will be interpreted as being in meters, not in the units currently being used by the program.
Diameters are interpreted as being in the units specified by the second unit specifier. If no second unit specifier is present, they will be interpreted as being in the same units as the end coordinates. The diameter of any wire may be given as AWG wire size, using #n where n is an integer > 0. (n can have more than one digit.) The optional segmentation field can contain the number of segments for the wire or the letter "M". "M" will result in minimumrecommended count automatic segmentation for the wire. If the segmentation field is blank, or contains any other non-numeric value, zero, or a negative number, the wire will be automatically segmented using "conservative" criteria.
Fields beyond the eighth will be ignored.
: EZNEC+, EZNEC
This format is provided to allow easy importing of wire coordinates from an
NEC input file.
Only GW lines are read. EZNEC will assume this format if it finds any line in the file beginning with GW.
The standard NEC format is required: GW followed by the tag (ignored), number of segments, end coordinates, and radius (not diameter). No fields are optional, and U.S. format is required. If any line is found beginning with
"GW", the file is assumed as being GW format, and all other lines in the file, including dimension specifications, are ignored, and all values are assumed to be meters. Comments can follow the data on the line by preceding the comment with an exclamation point. This format enables importing wires
(only) directly from an NEC file, or from GW lines cut and pasted from one.
Note that EZNEC pro programs allow direct reading of NEC format files, including most of the other “card” types, so this method of input isn’t usually necessary.
The licensee ("Licensee" or "User") acknowledges that the reliability of any and all results produced by this software are not precise and are subject to significant levels of variability. Licensee further acknowledges that the reliability of results can be affected by a multitude of factors, including the type of antenna used, whether it is used in an urban environment, surrounding objects, ground conductivity conditions, and the experience and skill of
Licensee in using computer modeling techniques. Licensee specifically acknowledges that this software CANNOT BE USED TO tell User whether (1) the amount of electromagnetic energy being emitted from User's antenna is unsafe to User, User's family, User's neighbors or anyone else in proximity to
User's antenna; (2) Licensee's antenna subjects Licensee or any other persons to potentially hazardous electromagnetic exposure. Licensor, therefore, makes no warranties that this software provides any information regarding human safety or whether exposure hazardous to humans may result from use of Licensee's antenna; Licensee acknowledges he or she is not relying on this software to determine whether User's antenna is safe or subjects any persons to hazardous or potentially hazardous exposures of electromagnetic energy.
LICENSOR HEREBY DISCLAIMS ANY AND ALL WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
LICENSOR'S LIABILITY UNDER OR FOR BREACH OF THIS AGREEMENT
SHALL BE LIMITED TO REFUNDING THE LICENSE FEE PAID BY
LICENSEE. IN NO EVENT SHALL LICENSOR BE LIABLE FOR SPECIAL,
CONSEQUENTIAL, OR INCIDENTAL DAMAGES, HOWEVER CAUSED,
WHETHER FOR BREACH OF WARRANTY, NEGLIGENCE, CONTRACT,
TORT (INCLUDING STRICT LIABILITY) OR OTHERWISE, OR FOR
PERSONAL INJURY OR FOR PROPERTY DAMAGE. BY USE OF THIS
SOFTWARE, LICENSEE HEREBY ACKNOWLEDGES AND AGREES THAT
HE OR SHE WILL BE SOLELY RESPONSIBLE FOR ANY INJURIES
ARISING OUT OF OR RELATING TO ELECTROMAGNETIC ENERGY
EMITTING FROM USER'S RADIO ANTENNA. USER WILL
INDEPENDENTLY SATISFY HIMSELF/HERSELF THAT USER'S RADIO
ANTENNA DOES NOT EXPOSE ANY PERSONS TO HAZARDOUS LEVELS
OF ELECTROMAGNETIC ENERGY AND DOES NOT SUBJECT ANY
PERSONS TO UNSAFE CONDITIONS. USER WILL DEFEND, INDEMNIFY,
AND HOLD LICENSOR HARMLESS FROM ANY AND ALL CLAIMS
RELATING TO ELECTROMAGNETIC ENERGY EMITTED FROM USER'S
ANTENNA INCLUDING, WITHOUT LIMITATION, CLAIMS THAT THE LEVEL
OF SUCH EMISSIONS IS UNSAFE. LICENSEE RELEASES LICENSOR
FROM ANY CLAIMS RELATING TO THE INABILITY OF THIS SOFTWARE
TO DETERMINE WHETHER LEVELS OF ELECTROMAGNETIC ENERGY
COMING FROM LICENSEE'S ANTENNA ARE HAZARDOUS OR UNSAFE
TO ANY HUMAN BEINGS.
EZNEC User Manual
SINGLE USE SOFTWARE LICENSE AGREEMENT
By using the software, the user agrees to the following terms and conditions.
Ownership. All ownership of this software is reserved to Roy W. Lewallen
("Licensor"). No title to or ownership of any software or any parts thereof is transferred by any delivery of this software. The use of the software enclosed with this License Agreement conclusively establishes Licensee's agreement with all the terms and conditions hereof.
Limitation of Liability. Licensor's liability under this Agreement shall be limited to a refund of the price paid by Licensee for the use of such program.
Licensor will not be liable for any property damage, personal injury, loss of use, interruption of business, or other special, incidental, or consequential damages, however caused, whether for breach of warranty, contract, tort
(including negligence), strict liability or otherwise.
Exclusion of Warranties. Licensor excludes all warranties, express or implied, including, without limitation, warranty of fitness for a particular purpose.
Licensor's sole warrantee is as follows: For a period of ninety (90) days following delivery, the Licensor will refund the full purchase price upon notification that the Licensee is not completely satisfied with the program and upon receipt by the Licensor of all hardware keys furnished with the program.
Except as stated in the previous sentence, licensor does not warrant that the functions contained in the program will meet the licensee's requirements.
Licensor makes no other warranties of merchantability or fitness for a particular purpose.
Use of Licensed Software. Licensor is licensing Licensee to use the software as a single user. No use of this software may be made on a company or location basis including, without limitation, local area networks.
Modification/Copies. Licensee may make copies of the licensed program, but no more than one copy per license may be used at any one time. Any modification of this licensed software program by Licensee shall remain subject to all terms and conditions of this Agreement and shall remain the sole property of Licensor; all derivative works shall remain the property of Licensor.
Protection. During the term of this Agreement, or thereafter, in the event
Licensee uses or conveys, or attempts to use or convey, the licensed program, manual, and/or technical documentation or any duplication or modification thereof, in a manner contrary to the terms of this Agreement,
Licensor shall be entitled to an injunction to be issued by any court of equity in joining and restraining Licensee from continuing said violation, in addition to any damage suffered by Licensor. The provisions of this section shall survive any termination of this agreement.
General Terms. The prevailing party in any legal action brought under this
Agreement shall be entitled to reimbursement for reasonable attorney's fees at trial, on appeal and on any petition for review.
Miscellaneous. This instrument contains the entire agreement between the parties respecting its subject matter and may only be modified in a writing signed by Licensor and Licensee. This agreement is governed by the laws of
Oregon. Any legal action arising out of this Agreement shall be prosecuted in
Oregon. Licensee submits to the jurisdiction of the courts of Multnomah
County, Oregon. No waiver by Licensor of any violation or nonperformance by
Licensee shall be deemed to be a waiver of any subsequent violation or nonperformance. All waivers must be in writing. In the event any of the provisions of this License Agreement are invalid under any applicable statute or rule of law, those provisions or portions thereof are to that extent deemed to be omitted, or shall be interpreted, if possible, to comply with such statute or rule of law.
Copyright and Trademark Notice
EZNEC v. 4.0 and EZNEC pro programs EZNEC-M and EZNEC/4 v. 4.0 and their manual and on-line help are copyright © 2000-2007 by Roy W. Lewallen.
All rights are reserved.
is a registered trademark of Roy W. Lewallen. All rights are reserved.
EZNEC/4 may use a modified version of NEC-4.1 for calculations. The following warning and notice apply to the portion of that program derived from
NEC-4.1. Read the following important messages before using.
*********** WARNING **********
The NEC-4.1 code is subject to export restrictions under Department of
Commerce regulations EAR99 (15 CFR Parts 730-774).
*********** NOTICE **********
The NEC-4.1 computer code material was prepared as an account of work sponsored by an agency of the United States Government. Neither the United
States Government nor the University of California nor any of their employees makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately-owned rights.
Third Party Software Legal Notices
All EZNEC program types beginning with v. 4.0.9 incorporate code generously provided free of charge by vbAccelerator. The following information constitutes the license agreement for use of that software: vbAccelerator code and binaries are provided for your reuse in any of your projects, whether proprietary, commercial or open-source. This document details vbAccelerator's Open Source software licence. vbAccelerator Software License
Copyright (c) 2002 vbAccelerator.com
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
EZNEC User Manual
3. The end-user documentation included with the redistribution, if any, must include the following acknowledgment:
"This product includes software developed by vbAccelerator
Alternately, this acknowledgment may appear in the software itself, if and wherever such third-party acknowledgments normally appear.
4. The names "vbAccelerator" and "vbAccelerator.com" must not be used to endorse or promote products derived from this software without prior written permission. For written permission, please contact vbAccelerator through [email protected]
5. Products derived from this software may not be called "vbAccelerator", nor may "vbAccelerator" appear in their name, without prior written permission of vbAccelerator.
THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
VBACCELERATOR OR ITS CONTRIBUTORS BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
All EZNEC program types beginning with v. 4.0.14 make use of unzip32.dll, generously provided free of charge by Info-ZIP. The following information constitutes the license agreement for use of that software:
This is version 2004-May-22 of the Info-ZIP copyright and license. The definitive version of this document should be available at ftp://ftp.infozip.org/pub/infozip/license.html indefinitely.
Copyright (c) 1990-2004 Info-ZIP. All rights reserved.
For the purposes of this copyright and license, "Info-ZIP" is defined as the following set of individuals:
Mark Adler, John Bush, Karl Davis, Harald Denker, Jean-Michel
Dubois, Jean-loup Gailly, Hunter Goatley, Ian Gorman, Chris Herborth,
Dirk Haase, Greg Hartwig, Robert Heath, Jonathan Hudson, Paul
Kienitz, David Kirschbaum, Johnny Lee, Onno van der Linden, Igor
Mandrichenko, Steve P. Miller, Sergio Monesi, Keith Owens, George
Petrov, Greg Roelofs, Kai Uwe Rommel, Steve Salisbury, Dave Smith,
Christian Spieler, Antoine Verheijen, Paul von Behren, Rich Wales,
This software is provided "as is," without warranty of any kind, express or implied. In no event shall Info-ZIP or its contributors be held liable for any
Legal Notices direct, indirect, incidental, special or consequential damages arising out of the use of or inability to use this software.
Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:
1. Redistributions of source code must retain the above copyright notice, definition, disclaimer, and this list of conditions.
2. Redistributions in binary form (compiled executables) must reproduce the above copyright notice, definition, disclaimer, and this list of conditions in documentation and/or other materials provided with the distribution. The sole exception to this condition is redistribution of a standard UnZipSFX binary (including SFXWiz) as part of a selfextracting archive; that is permitted without inclusion of this license, as long as the normal SFX banner has not been removed from the binary or disabled.
3. Altered versions--including, but not limited to, ports to new operating systems, existing ports with new graphical interfaces, and dynamic, shared, or static library versions--must be plainly marked as such and must not be misrepresented as being the original source. Such altered versions also must not be misrepresented as being Info-ZIP releases-including, but not limited to, labeling of the altered versions with the names "Info-ZIP" (or any variation thereof, including, but not limited to, different capitalizations), "Pocket UnZip," "WiZ" or "MacZip" without the explicit permission of Info-ZIP. Such altered versions are further prohibited from misrepresentative use of the Zip-Bugs or Info-ZIP email addresses or of the Info-ZIP URL(s).
4. Info-ZIP retains the right to use the names "Info-ZIP," "Zip," "UnZip,"
"UnZipSFX," "WiZ," "Pocket UnZip," "Pocket Zip," and "MacZip" for its own source and binary releases.
Updates (Maintenance Releases)
Updates to EZNEC and EZNEC+ (but not EZNEC pro programs EZNEC-M and EZNEC/4) and the manual are posted at http://eznec.com/ez40updates as they’re developed. EZNEC pro users will find the update URL on the CD-
ROM label. Please check the appropriate URL periodically to keep your program up to date. These aren’t upgrades to new versions, but include fixes for bugs as they’re found, and improvements to the manual. Up-to-date information about EZNEC, EZNEC+, and EZNEC pro will be posted there or elsewhere at http://eznec.com
Have you checked lately for updates? A bug might have already been found
section for information.
Although EZNEC has been extensively tested, there are bound to be bugs remaining. If you encounter one and report it, I’ll fix the bug as quickly as possible and send you a replacement program. However, Windows is a complex environment, and it can sometimes be very difficult to determine the exact sequence of events leading to a crash or other problem, so your help is essential.
The key to fixing a bug lies in being able to make it occur. If I can make it happen, I can fix it. If I can’t make it happen, it’s usually virtually impossible to infer the cause. In the Windows environment, a problem can occur only when certain windows overlap in a particular way or in a particular order, or only when certain windows are open. So it’s important to get as much detailed information as possible about the state of the program when the problem occurs.
The following information is very important, so please include as much of it as you can in your report:
1. Error messages. Please record the exact wording of the error message, and the title on the colored bar at the top. (The title helps determine what generated the message.) Often, some or all of the program’s windows remain on the screen while the error message is being displayed. So this gives you an opportunity to record what forms
(windows) are open, their approximate sizes, and where they’re positioned. Of course, some bugs won’t generate an error message. If it doesn’t, that’s useful information in itself, so please include it.
2. What you were doing, in as great detail as you can remember, when the error occurred. This includes not only the very last action, but as much as you can recall of the events which led up to it.
3. Is it repeatable? This is essential information. A repeatable error is very much easier to find than one which isn’t. Please try to begin exactly as you did and follow as closely as possible the sequence of operations you performed, and see if you can make it happen again. If so, please record the sequence. Note that some errors depend on which windows are open, and sometimes even which windows are overlapping, so this information can be important also.
4. Does it happen only with a particular antenna description or descriptions? If so, please attach the .EZ file to an email message and send it to me.
5. If there was anything new, different, or unusual you were doing.
Thanks for your help!
How to Contact Me
The best method of contacting me is email, but other means might be better for you.
Email: [email protected]
P.O. Box 6658
Beaverton, OR 97007
2D ...............................22, 107, 108
2D Display ............22, 93, 102, 107
Showing frequency on.............93
2D Pattern...........................22, 105
Showing in the View Antenna
2D Plot Scale ..............................93
2D Slice ....................................108
3 dB beamwidth ........................107
3D Display ..................22, 102, 108
A Few Words About Copy
About EZNEC .............................99
About Ground Models .................67
About Transmission Lines...........64
About Wires ................................31
Action buttons .....................91, 101
Setting font size and type ......122
Adding A Description ............80, 92
Adding A Trace .........................102
Advanced Wire Features
Along The Straightaway..............13
Alt SWR Z0 .........................99, 109
Amateur or Professional? .............4
Antenna Height ...........................34
Antenna Notes ........27, 79, 92, 122
NEC file CM...........................122
Anti-adware Programs ..............120
ARRL Type Plot Scale ................93
Auto Coord Match.......................93
Auto Coordinate Match ...............31
Auto Seg .....................................88
Automated Radial Creation.........49
Automatic Segmentation.......33, 79
Average Gain.................. 44, 56, 80
Detecting source placement problems..............................56
Azimuth Rotate End....................37
Back Yard Dipole ........................13
Balun ..........................................44 bmp Files ..................................105
Buried Radials ......................41, 46
Buried Wires .........................41, 71
Calculating Engine Type ...........121
Calculation Time .........................99
Center of wire x end segment within wire y.............................84
Change Coordinate By ...............37
Change Height By.......................34
Change Length By ......................37
Change Length To ......................37
Change Units ..............................34
Retain Numbers ......................34
Characteristic Impedance ...........66
Transmission line ....................66
Circular Polarization................7, 77
Loop minimum ..............................45
Closely Spaced Wires.................42
CM ................................ 27, 79, 122
Coaxial Cable .............................67
EZNEC User Manual
Combining Antenna Descriptions
Comma-delimited files ..................5
Common Features ....................102
Compass Bearing .......................93
Compatibility among versions .....26
Component Version Numbers.....99
Connect End To ..........................37
Connecting Sources to Ground...58
Connecting to High Accuracy
Connecting Wires to Ground.68, 72
Control Box ...............................102
Control Center ..91, 92, 93, 99, 101
Options menu ..........................93
Control Window.........102, 105, 108
Controlling Memory Use ...........114
Coord Entry Mode.......................34
Coordinate Sytem .......................31
Copy Protection ............................3
Copyright Notice .......................137
Creating Graphics Files ............105
Current balun ..............................44
Current Phase.....................75, 105
Current Phase Markers.............105
Currents ................59, 75, 101, 105
Showing in the View Antenna
Currents Table ............................75
2D Display .............................107
Data Lines.........................102, 107
Data Window ............102, 105, 107 dBi.........................................77, 93 dBref ............................... 77, 93, 99
Decimal Separator ................5, 130
Frequency sweep input file....130
Default Ground Const .................93
Deleting A Trace .......................102
Description File ...........................92
Combining (adding)...........80, 92
Desktop Shortcut ........................11
Disk Use As Virtual RAM ..........121
Display Window ........................102
Divide Length By.........................37
DOS EZNEC.........................28, 29
Operational differences ...........28
Double Precision Operation ......119
E Field ..................................77, 86
Edit Menu ...................................93
Antenna Notes ........................92
Elevated Radial Systems ............43
Elevation Rotate End ..................37
End Coordinates .........................34
Ending EZNEC ...........................92
Entering and Modifying Ground
Entering and Modifying
Transmission Lines .................66
Exit - Normal ...............................92
Exit Without Saving.....................92
External NEC-4 Engine.............116
Using with EZNEC/4..............116
EZNEC..........................26, 92, 140
Previous versions ....................26
EZNEC components ...................30
EZNEC Editor .............................81
EZNEC Pro ...............................109
Differences from NEC-2 and
EZNEC Pro And NEC ...............109
EZNEC Pro Section Note..........109
EZNEC Pro Users.......................11
EZNEC v. 1 and 2 .......................29
Files which can be deleted ......29
EZNEC.INI ..................99, 114, 122
Double precision NEC-4 engine
Far Field Patterns .......................78
Far Field Table............................77
Far Field Table Units.............77, 93
Fast Analysis Ground Type...........7
Feedlines and Baluns .................44
Feedpoint Resistance .....45, 46, 76
Negative ............................45, 76
Small loop ...............................45
FF Plot ......................................101
FF Tab ................................77, 101
Field - E and H ......................77, 86
File ................................92, 99, 124
.PF format .............................124
Last opened or saved..............99
Files ......................................5, 110
NEC format ...........................110
Fix Segs ......................................88
Flat Surface Modeling ...........48, 50
Control Center Action Buttons setting ................................122
Printed plot data ......................93
Printer vs screen .....................81
Free Space .................................67
Freq Swp ..................................101
Frequency................. 22, 87, 93, 99
Rescaling ..........................22, 87
Showing on 2D Display ...........93
Frequency Sweep. 81, 99, 101, 121
Data (output) file......................81
Input file ..................................81
Maximum steps in Smith chart program file..................81, 130
Frequency Sweep Input File81, 130
Decimal separator .................130
Frequency Sweep setup .......81, 99
Turning on and off ...................81
Front/Back Ratio .......................107
Getting Acquainted with EZNEC.10 gif Files .....................................105
GM NEC .....................................51
Gnd Wave Dist............................85
Graphics Windows Overview ...101,
Graphics Windows Sections .....102
Grid Spacing ...............................50
Ground................ 46, 58, 68, 72, 99
Connecting Wires..............68, 72
Ground characteristics..........68, 71
EZNEC User Manual
Ground Descrip.....................68, 99
Ground File Tolerance ................93
Ground loss ..........................67, 80
Evaluating with Average Gain .80
Ground Media .............................71
Using two ................................71
Ground Type .........................67, 99
Ground Types .......................67, 68
Free space ..............................67
Reflection coefficient ( .......7, 110
Ground Wave Analysis .........85, 99
Observation height ..................99
Group Modify ........................34, 86
GS NEC ......................................51
GX NEC ......................................51
H Field ..................................77, 86
Antenna changing ..............................34
Helix Creation .............................50
Help Menu ..................................99
High Accuracy Ground41, 46, 68,
Highlighting a 2D.......................108
How to Contact Me ...................141
How to Do It ..........................34, 55
If You Downloaded EZNEC ........10
Importing Wire Coordinates From
ASCII File ....................34, 40, 92
File Format ............................131
Information Window ..............91, 99
Insulated Wire .............................39
Introduction to Modeling..............30
Inverted Vee Antenna .................18
J jpeg Files ..................................105
Laplace Load Type ...............60, 61
Laplace Loads Window...............64
Laplace Type Loads ...................64
Large Models ............................113
Last File Opened or Saved .........99
LastZ.txt .................... 5, 81, 89, 121
LastZ.txt file ..............................121
Legal Disclaimers ............. 135, 137
Wire................................. 34, 105 changing ..............................37
Limitations of Real Ground Models
Linear dB Plot Scale ...................93
Linear Loaded Antennas.......44, 48
Voltage and current.................76
Load Data ...........................76, 101
Load Types ... 27, 59, 60, 61, 62, 64
Laplace .............................60, 64
R + j X ...............................60, 62
RLC ............................. 27, 60, 62
Loading Coils ..............................61
Loads .............................. 27, 61, 99
Placing at wire junctions..........61
Placing on segments...............61
Total number of in current model
Loads Overview ..........................59
Loads Window ............................59
Loads Windows ....................61, 99
Log Periodic Antennas................44
Loop Antenna .............................45
Minimum circumference ..........45
Loop Creation .............................49
Loop Resizing .............................49
Maintenance Releases .............140
Making a Desktop Shortcut.........11
Manual ....................................1, 10
MaxMSFreqs ......................81, 122
McAfee Antivirus .......................120
Media Window ............................71
Controlling use by EZNEC pro
Used by EZNEC pro..............114
Memory Information ....................99
DOS EZNEC ...........................27
MicroSmith ....................81, 93, 130
Maximum .DAT file steps81, 122,
MININEC-type ground.....46, 68, 86
DOS EZNEC ...........................28
Modeling Coaxial Cable ..............67
Modeling Flat Surfaces .........48, 50
Modeling Wires ...........................31
Very large ..............................113
Monitor Recommendations .........26
Moving Wires ..............................34
Multiband Antennas ....................45
Multiply Length By.......................37 mV/m ..........................................77
Near Field ...................................99
Near Field Analysis .........68, 77, 86
Near Field Table .........................77
Near Field Table Format .............93
Differences from EZNEC pro.109
NEC ....................................51, 110
NEC 'Card' Entry.........................51
NEC Format Files .....................110
Reading and writing ..............110
NEC Radial Model .......... 46, 71, 73
NEC reflection-coefficient Ground
NEC Sommerfeld Ground ...........68
NEC-4 ......................... 93, 116, 119
Double precision calculating engine................................119
External using with EZNEC/4 ..........116
NEC-4 Notices ..........................137
NEC-format files ...............5, 27, 31
Decimal separator .....................5
Opening and saving ................31
Norton Antivirus ........................120
Notes For International Users .......5
Objects ....................... 93, 102, 105
View Antenna Display93, 102,
Observation Height ...............85, 99
On The Race Course..................22
Open Description ........................92
Opening The Description File .....31
OpenPF Plot File Format ..........124
Viewing OpenPF files ..............90
Other Wire Considerations .........40
Parallel Type RLC Loads ............62
Patches............................. 109, 140
Perfect Ground ...........................67
EZNEC User Manual pf Format Files ..........................124
Conversion to Graphics Format
Translating from .ENT format ..90
Phased Arrays ......................45, 59
Placing Loads At Wire Junctions.61
Placing Loads On Segments ......61
Placing Sources At Wire Junctions
Placing Sources On Segments ...57
Step size .................................99
Translating file format..............90
Plot Data Font .............................93
Plot File Types ..........................102
Plot Line Width............................93
Plot Printing ........................93, 122
Plot Window ..............................102
Circular ................................7, 77
Shown in 2D display..............107
Power Level ................................93
Power Level selection .................93
Printing The Antenna Description98
Printing The Manual....................11
Printing Wire Coordinates .....34, 98
R + j X Load Type ...........60, 61, 62
R + j X Loads Window ................62
R Freq Column............................62
Radial Creation ...........................49
Radials......................43, 46, 49, 73
Controlling use by EZNEC pro
Used by EZNEC pro..............114
Virtual ....................113, 114, 121
Read Frequencies From File ......81
Real Ground Models.............67, 70
Real Ground Types.....................68
Ref Level ....................................99
Reflection Coefficient (..........7, 110
Reporting bugs .........................140
Resistance ...................... 45, 62, 76
Frequency dependent .............62
Negative ............................45, 76
Reverse Connection ...................66
RLC Load Type......... 27, 60, 61, 62
RLC Loads Window ....................62
Rotating wires .............................37
Save As ....................................101
Save As Default ..........................93
Save Description As ...................92
Saving A Trace .........................102
Scaling To a New Frequency......87
Segment Dots ...........................105
Segment Length33, 41, 42, 45, 79,
Segment Length Tapering41, 43,
Segmentation...... 33, 42, 43, 79, 88
Log periodic antenna...............44
Segmentation Check31, 79, 88, 93,
Segmentation Check Warnings .50,
After creating wire grid ......50, 88
Segments ........... 33, 34, 43, 45, 99
Length displaying.....................34, 105
Maximum number of ...............33
Specifying number of ........33, 34
Total number in current model 99
Selected Operational Differences28
Selecting Wires...................34, 105
Selection buttons ........................91
Series RLC .................................62
Series Type RLC Loads..............62
Setups ..................................86, 99
Near field analysis ...................86
Desktop for starting EZNEC...............11
Shortcuts.........................28, 34, 37
DOS EZNEC ...........................28
Wire coordinate entry ........34, 37
Show Calculation Time ...............99
Show Description ........................98
Show Freq on 2D Plot.................93
Show Ground Info .......................99
Show Memory Info ......................99
Show Temp Dir Space ................99
SINGLE USE SOFTWARE
LICENSE AGREEMENT .......136
Small Loops ................................45
Smith Chart .................................81
Smith Chart Program selection ...81
Smith Chart Programs ........93, 130
MicroSmith ......................93, 130 winSMITH........................93, 130
Software Incompatibilities .........120
Source ................18, 58, 59, 76, 93
Absolute vs. relative value.......93
Split .............................18, 58, 59
Voltage and Current ................76
Source Data ................................76
Source Placement42, 44, 54, 56,
57, 58, 80
And Average Gain ...................80
At wire junctions ......................58
On Segments ..........................57
Source Placement Precautions..44,
Sources.........54, 55, 57, 58, 59, 99
Connection to other EZNEC components .........................54
Copying and moving................55
Special Options...................99, 122
Split Source .................... 18, 58, 59
Src Dat................................76, 101
Starting EZNEC ..........................11
Step Size ....................................99
Stepped Diameter Correction ....44,
48, 51, 53, 87, 89, 93, 121
Stepped Diameter Correction
Stepped Diameter Correction
Transmission line ....................66
Support .............................140, 141
How to contact me ................141
SWR ............................. 76, 99, 101
Setting alternate Z0.................99
SWR Display......... 22, 89, 102, 109
SWR Graph .................. 22, 89, 109
SWR Sweep .......................22, 101
Taper Segs .................................87
Temporary Directory ...................99
Available space .......................99
Test Drive ....................... 13, 18, 22
Along The Straightaway ..........13
On The Race Course ..............22
Through The Curves ...............18
Test Drive Introduction................13
The Big Difference ......................26
The Calculation Progress Window
The Laplace Loads Window .......64
The NEC Radial Model ...............73
The R + j X Loads Window .........62
The RLC Loads Window .............62
EZNEC User Manual
Third Party Software Legal Notices
Thousands separator ....................5
Through The Curves ...................18
Adding to the 2D Display .......102
Removing from the 2D Display
TraceView .............................90, 99
Trans Lines .................................99
Transmission Line Model ............64
Transmission Line Models ..........44
Transmission Lines44, 59, 64, 66,
67, 99, 105
Actual distance between ends.66
Dielectric insulated ..................66
Electrical length .......................66
Physical length ........................66
Showing in the View Antenna
Total number in current model.99
Transmission Lines Window .66, 99
Trap ................................48, 61, 62
Trap Type RLC Loads.................62
Uninstalling DOS EZNEC ...........29
Far field table...........................93
Updates (Maintenance Releases)
Upgrading from previous versions
Using An External NEC-4 Engine
(EZNEC/4 Only) ....................116
Using Multiple Sources ...............59
Using The 2D Display ...............107
Using The 3D Display ...............108
Using the Stepped Diameter
Using The SWR Display ...........109
Using The Wires Window ...........34
Using Two Ground Media ...........71
Velocity Factor ............................66
Version Numbers ........................99
Vertical Antennas And Buried
Very Large Models....................113
View Ant ...................................101
View Antenna Display93, 101, 102,
Objects .......................... 102, 105
Selecting wires ......................105
Virtual RAM............... 113, 114, 121
What's New in v. 4.0 .....................7
Basic operation .........................1 winSMITH ..................... 81, 93, 130
Maximum frequency steps .....81,
Length changing ..............................37 displaying.....................34, 105
Wire Coordinate File .................131
Wire Coordinate Shortcuts..........37
Wire Coordinates .... 34, 37, 98, 131
ASCII File Format..................131
Importing from ASCII file34, 40,
Printing ..............................34, 98
Wire Diameter .............................34
Wire Grid Creation ..........48, 50, 88
And Segmentation Check
Warnings .......................50, 88
Wire Grid Modeling ...............48, 50
Wire Information..................34, 105
Wire Insulation ............................39
Wire loss .........................38, 80, 99
Evaluating with Average Gain .80
Wire Numbers .....................93, 105
Wire spacing ...............................42
Wires31, 34, 40, 41, 68, 72, 92, 99,
Connecting to ground ........68, 72
Importing from ASCII file .........92
Intersecting at an acute angle .41
Selecting ......................... 34, 105
Total number in current model 99
Wires Window.......................34, 99
Working With NEC Format Files
Yagi ................................ 48, 51, 89
Yagi Antennas ......................48, 89
Specifying alternate value for
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