F
IRST LOOK
New Product Reviews
Basic Antennas:
Understanding Practical
Antennas and Design
By Joel R. Hallas, W1ZR
Notes on the back of this book promise:
“A comprehensive introduction to antennas –
basic concepts, practical designs, and details of
easy to build antennas.” Happily, author Joel
R. Hallis, W1ZR, delivers on that promise.
If you’re willing to give this book some
serious time and thought,
you will be rewarded with
an excellent introduction
to what makes antennas
tick and a useful survey of
many practical antenna designs. The designs covered
are for antennas common
to applications from highfrequency on into the microwave region of the
radio-frequency spectrum. And you’ll even find
directions for building some of those designs
yourself.
The book begins with an introduction
to radio-frequency current and explains that
this current flowing in a conductor leads to
the radiation of radio waves. Discussions of
factors such as antenna radiation patterns, antenna feed-point impedance, and the effect of
the earth beneath the antenna on these factors
prepares the reader to understand the discussions of the performance of the various antenna
designs which follow.
After introducing the basic half-wavelength dipole antenna, the author builds on this
introduction to present various designs utilizing
dipole elements in other antennas. As the book
progresses, a wide variety of antenna designs
are presented, along with discussions of their
operating characteristics.
By the book’s end, the reader is acquainted
with various vertical and horizontal antenna designs, linear-element beams, surface-reflector
beams, parasitic-reflector beams, long-wire
antennas, large and small loop antennas, logperiodic designs, slot antennas, patch antennas, and multiband and wideband antennas, as
well as a number of other antenna designs. In
addition, the basics of such related topics as
MT READERS ONLY
To access the restricted website for the month of March,
go to www.monitoringtimes.com, click on the key,
and when prompted, enter
“mtreader” under the user
name. Your password for
March is “harrier” – Check
in each month for new material!
68
MONITORING TIMES
March 2009
transmission lines, wave guides, antenna measurements, and computer modeling of antennas
are introduced.
The information in this book is presented
as a natural progression of ideas in which new
facts build upon those previously presented. As
an example, the section on loop antennas begins
by developing the idea of a large square loop
and discussing its characteristics. Then loops
of other shapes are covered and their radiation
patterns discussed. Following this, small loops
are introduced, and their functioning contrasted
to that of large loops.
Moving on to the practical side of loop
antennas, the next chapter gives instructions
for building and operating large loops such as
quad loops and cubical-quad beams, as well as
small table-top loops. This logical development
of ideas is an obvious benefit to understanding
the technical ideas covered in a text on antennas.
Basic Antennas, like most technical books,
presents concepts that may require some
thought and reflection by the reader. It is not
an engineering text, but it is a technical book,
and skimming through it will miss much of the
value the book has to offer. On the other hand,
after reading and digesting its contents, you
will have a good grasp of the basic factors in
antenna performance.
You will also be familiar with a broad sampling of useful antenna designs. And you will
have something else that most radio enthusiasts
want: you will know how to consider the factors
you’ve learned from this text when choosing,
and (for some of the designs) even building
antennas for your communication needs.
This will be a book you will keep on your
shelf and reach for frequently as you continue
your adventures in the fascinating field of
radio-communication antennas.
The Basic Antennas book is available from
the ARRL Bookstore at www.ARRL.org or call
888-277-5289. This first edition is © 2008, The
American Radio Relay League, Inc. (ISBN:
0‑87259‑999‑X) #9994 ‑‑ $29.95.
Reviewed by MT columnist
W. Clem Small, KR6A.
AOR AR-STV Wireless
Camera Detector
With growing concerns for both safety
and security, video cameras are being placed
in large numbers throughout the country. But
are all these cameras in your best interest?
Are some cameras meant to compromise your
own privacy? You can perform your own surveillance for these intrusive devices with an
affordable new product.
AOR has just released a hand-held wireless camera detector, basically a TV receiver
with continuous tuning from 900-2800 MHz
(2.8 GHz), to intercept analog signals
of these devices and even display their
picture in full color on its 2.5” LCD
screen. A 3.5 mm video output jack
accommodates an external monitor.
The receiver automatically sweeps
its programmable frequency bands
looking for signals, displaying detected signals
as spikes on a spectrum
analyzer screen. Set in
the manual mode, the
user may step through
the frequency range in
any preset interval between 2 and 10 MHz
in 1 MHz increments.
Ten search banks allow
user-selectable search
ranges, and 10 memory
channels allow storage
of discrete frequencies.
Detectable formats include NTSC, PAL, CCIR, EIA, and
scrambled/reverse polarity video signals often
encountered on 1.2 GHz L band and 2.4 GHz
S band (WiFi). Typical sensitivity is -80 dBm
@ 2.4 GHz.
The operator may select the video quality
threshold level for display, as well as the acceptable level of noise interference.
Images may be time stamped and recorded
at the press of a button, and up to nearly 2000
images can be stored on an optional, plug-in
SD memory card. A USB port allows transfer
into a computer for image storage.
The receiver measures 2.6”W x 5.2”H x
1.3”D and weighs 15 oz. It is powered either
externally by 6VDC, or internally by four AA
alkaline or rechargeable NiMH cells (provided).
❖ Our Test
Don’t expect subversive video surveillance cameras at every turn; they are few and
far between. Our search through a small town
revealed none in use at Wal-Mart, Lowe’s,
banks, stores, or anywhere else in the commercial divisions. Such installations generally
have AC power, and their surveillance cameras
are commonly connected through coax cable.
But for law enforcement applications to
test known wireless cameras, or to search for
suspect cameras in remote areas where a cabled
video installation is unlikely, but where wireless cameras might possibly be placed, this is
the debugging instrument to take along!
The AR-STV comes with instruction
manual, rubber flex antenna with SMA base,
belt clip, and rechargeable NiMH cells. It sells
for $869.95 at Grove Enterprises (800-4388155 or www.grove-ent.com) and other AOR
dealers.
Review by MT Publisher Bob Grove