495P GPIB

Instrument Serial Numbers
Each instrument manufactured by Tektronix has a serial number on a panel insert or tag, or stamped on the
chassis. The first letter in the serial number designates the country of manufacture. The last five digits of the
serial number are assigned sequentially and are unique to each instrument. Those manufactured in the
United States have six unique digits. The country of manufacture is identified as follows:
B010000
E200000
J300000
H700000
Tektronix, Inc., Beaverton, Oregon, USA
Tektronix United Kingdom, Ltd., London
Sony/Tektronix, Japan
Tektronix Holland, NV, Heerenveen, The Netherlands
Instruments manufactured for Tektronix by external vendors outside the United States are assigned a two digit
alpha code to identify the country of manufacture (e.g., JP for Japan, HK for Hong Kong, IL for Israel, etc.).
Tektronix, Inc., RO. Box 500, Beaverton, OR 97077
Printed in U.S.A.
Copyright © Tektronix, Inc., 1992. All rights reserved. Tektronix products are covered by U.S. and foreign
patents, issued and pending. The following are registered trademarks: TEKTRONIX, TEK, TEKPROBE, and
SCOPE-MOBILE.
WARRANTY
Tektronix warrants that this product will be free from defects in materials and workmanship for a period of
one (1) year from the date of shipment. If any such product proves defective during this warranty period,
Tektronix, at its option, either will repair the defective product without charge for parts and labor, or will provide
a replacement in exchange for the defective product.
In order to obtain service under this warranty, Customer must notify Tektronix of the defect before the
expiration of the warranty period and make suitable arrangements for the performance of service. Customer
shall be responsible for packaging and shipping the defective product to the service center designated by
Tektronix, with shipping charges prepaid. Tektronix shall pay for the return of the product to Customer if the
shipment is to a location within the country in which the Tektronix service center is located. Customer shall be
responsible for paying all shipping charges, duties, taxes, and any other charges for products returned to any
other locations.
This warranty shall not apply to any defect, failure or damage caused by improper use or improper or
inadequate maintenance and care. Tektronix shall not be obligated to furnish service under this warranty a) to
repair damage resulting from attempts by personnel other than Tektronix representatives to install, repair or
service the product; b) to repair damage resulting from improper use or connection to incompatible
equipment; or c) to service a product that has been modified or integrated with other products when the effect
of such modification or integration increases the time or difficulty of servicing the product.
THIS WARRANTY IS GIVEN BY TEKTRONIX WITH RESPECT TO THIS PRODUCT IN LIEU OF ANY
OTHER WARRANTIES, EXPRESSED OR IMPLIED. TEKTRONIX AND ITS VENDORS DISCLAIM ANY
IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
TEKTRONIX1 RESPONSIBILITY TO REPAIR OR REPLACE DEFECTIVE PRODUCTS IS THE SOLE AND
EXCLUSIVE REMEDY PROVIDED TO THE CUSTOMER FOR BREACH OF THIS WARRANTY. TEKTRONIX
AND ITS VENDORS WILL NOT BE LIABLE FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES IRRESPECTIVE OF WHETHER TEKTRONIX OR THE VENDOR HAS
ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.
This manual is one of a set of product manuals for the Tektronix 495 and
programmable 495P Spectrum Analyzers. The manual describes the instrument installation and operation. These instructions assume a thorough
knowledge of frequency domain analysis. The purpose of this manual is to
explain the operation of the 495 and 495P so that measurements will be
meaningful whether made under adverse or laboratory conditions. The
manual organization is shown in the Table of Contents. The manuals that are
available in addition to this 495/495P User Manual include the following:
•
495/495P Service Manuals, Volume 1 and 2
•
495P Programmer Manual (standard accessory for 495P Option only)
For manual ordering information, contact your local Tektronix Field Office or
representative or refer to the Accessories portion of the Replaceable Mechanical Parts list in the 495/495P Service Manual, Volume 2.
Standards and
Conventions
Most terminology is consistent with standards adapted by IEEE and IEC. A
glossary of terms is provided in Appendix A. Abbreviations in the documentation are consistent with ANSI Y1.1-1972. GPIB functions conform to the
IEEE 488-1978 standard. Copies of ANSI and IEEE standards can be
ordered from the Institute of Electrical and Electronic Engineers Inc.
Change/History
Information
Any change information that involves manual corrections or additional
information is located behind the Change Information page at the back of
this manual.
Unpacking and
Initial Inspection
Instructions for unpacking and preparing the instrument for use are described in Section 3.
Storage and
Repackaging
Instructions for short- and long-term storage and instrument repackaging for
shipment are described in Section 3.
495 & 495P User Manual
Preface
IF
Preface
495 & 495P User Manual
Table of Contents
/v
Contents
Table of Contents
Operation
495 & 495P User Manual
Table of Contents
vi
Contents
495 & 495P User Manual
vu
List of Figures
via
Contents
495 & 495P User Manual
flf
List of Tables
Contents
Please take a moment to review these safety precautions. They are provided
for your protection and to prevent damage to the spectrum analyzer. This
safety information applies to all operators and service personnel.
Symbols and Terms
These two terms a
PPear in manuals:
statements identify conditions or practices that could result in
damage to the equipment or other property.
| WARNING l statements identify conditions or practices that could result in
personal injury or loss of life.
These two terms appear on equipment:
495 & 495P User Manual
•
CAUTION indicates a personal injury hazard not immediately accessible
as one reads the marking, or a hazard to property including the equipment itself.
•
DANGER indicates a personal injury hazard immediately accessible as
one reads the marking.
XI
Safety
Specific PreC3UtionS
Observe all of these precautions to ensure your personal safety and to
prevent damage to either the spectrum analyzer or equipment connected to
it.
Power Source
The spectrum analyzer is intended to operate from a power source that will
not apply more than 250 VRMS between the supply conductors or between
either supply conductor and ground. A protective ground connection,
through the grounding conductor in the power cord, is essential for safe
system operation.
Grounding the Spectrum Analyzer
The spectrum analyzer is grounded through the power cord. To avoid electric shock, plug the power cord into a properly wired receptacle where earth
ground has been verified by a qualified service person. Do this before making connections to the input or output terminals of the spectrum analyzer.
Without the protective ground connection, all parts of the spectrum analyzer
are potential shock hazards. This includes knobs and controls that may
appear to be insulators.
Use the Proper Power Cord
Use only the power cord and connector specified for your product. Use only
a power cord that is in good condition.
Use the Proper Fuse
To avoid fire hazard, use only the fuse specified m the parts list for your
product, matched by type, voltage rating, and current rating.
Do Not Remove Covers or Panels
To avoid personal injury, do not operate the spectrum analyzer without the
panels or covers.
Electric Overload
Never apply to a connector on the spectrum analyzer a voltage that is outside the range specified for that connector.
Do Not Operate in Explosive Atmospheres
The spectrum analyzer provides no explosion protection from static discharges or arcing components. Do not operate the spectrum analyzer in an
atmosphere of explosive gases.
Xfi
Safety
Safety
XIV
Safety
Product Overview
The TEKTRONIX 495 and programmable 495P Spectrum Analyzers are high
performance, compact, portable instruments. Microcomputer control of most
functions simplifies and enhances operation.
The following is a list of the main instrument features:
•
Single and delta marker modes
•
Synthesizer frequency accuracy
•
Precision signal counting ability
•
Precise amplitude measurement capability
•
Digital storage display
•
Internal memory to retain front-panel settings and displays
•
HELP messages (CRT readout) that describe the function of front-panel
keys and controls as well as messages that explain operating errors
•
Front-panel DATA ENTRY push buttons
•
Ability to plot the display, readout, and graticule
•
Ability to hold 8 personalized macros in memory (programmable instruments only)
•
10 Hz to 3 MHz resolution
Basic Features
The frequency range is 100 Hz to 1800 MHz. A minimum resolution
bandwidth of 10 Hz, with a minimum span of 10 Hz/Div, provides measurement resolution that is proportional to the frequency accuracy. Digital storage provides flicker-free displays plus SAVE A, B-SAVE A, and MAX HOLD
to compare and subtract displays and save maximum values. In addition to
conventional digital storage features, internal memory stores up to nine
separate displays with their readouts and dot markers, which can be recalled later for additional analysis and comparison. It is also possible to
store up to ten different front-panel control setups for future recall. The
signal counting feature allows the instrument to selectively count a particular
signal out of several that may be present at its input.
495 & 495P User Manual
1-1
General Information
Select center frequency either by the front-panel CENTER/MARKER FREQUENCY control or by the Data Entry push buttons. When using the Data
Entry push buttons, it is not necessary to alter the Span/Div setting regardless of the frequency selected. Other parameters, such as vertical display
and reference level, are push button selectable with the flexibility previously
available only under program control of the general purpose interface bus
(GPIB).
Markers
The single and delta markers provide direct readout of frequency and amplitude information of any point along any displayed trace. Relative (delta)
frequency and amplitude information between any two points along any
displayed trace or between traces is also available. The CENTER/MARKER
FREQUENCY control can move the markers, or it can move the display with
a stationary frequency marker. For additional marker information, refer to
Using the Markers Feature in Section 6 of this manual.
Programmable Instrument Features
The programmable version of the instrument adds remote control capabilities to the manual instrument features. The front-panel controls (except
those intended exclusively for local use, such as INTENSITY) can be remotely operated through the GPIB port. This allows the spectrum analyzer to
be used with a variety of systems and controllers. Refer to the 495P Programmer Manual for additional information.
The programmable instrument also adds the macroinstructions (macros)
feature. The instrument memory has 8 kbytes reserved for the construction
of made-to-order macros. The macro menu can hold the titles of eight
macros for easy access. Specific macro information is located in the 495P
Programmer Manual.
Firmware Version and
Error Message
Readout
This feature provides a readout that identifies the version of firmware that is
installed. The readout is momentarily displayed when the power is turned
on. The programmable instrument will flash the firmware version, in addition
to the GPIB address, when the [RESET TO LOCAL] key is pressed.
If the instrument fails to complete any routine or function, an error message
will flash on the screen explaining the failure.
7-2
General Information
General Information
Accessories
The Replaceable Mechanical Parts list in the 495/495P Service Manual,
Volume 2, contains the part numbers, descriptions, and ordering information for all standard and optional accessories offered at this time.
The following list includes all standard accessories currently shipped with
each instrument. Refer to Section 7, Options, for alternate information.
Options
•
50 Q coaxial cable; N to N connector, 72 inch
•
50 0 coaxial cable; BNC to BNC connector, 18 inch
•
Adapter; N male to BNC female
•
4A fast-blow fuses1; 2 each
•
Power cord1
•
Cord clamp
•
CRT light filters; 2 - one each amber and grey
•
CRT mesh filter
•
Rear connector shield
•
495 & 495P User Manual
•
495P Programmer Manual; 495P Only
Section 7, Options contains information on all of the options currently available for the 495 and 495R
1
1f the instrument is wired for 220-240 V operation (Options A1, A2, A3, A4, AS) or if
Option 52 is installed (North American configuration for 220 V with standard power cord),
2A medium-blow fuses are used.
495 & 495P User Manual
7-3
General Information
1-4
General Information
This section includes the electrical, physical, and environmental characteristics of this instrument. Any instrument specification changes due to options
are listed in Section 7, Options.
Electrical
Characteristics
The following tables of electrical characteristics and features apply to the
spectrum analyzer after a 30-minute warmup, and after performing the
front-panel CAL adjustments, except as noted.
•
The Performance Requirement statements define characteristics that are
essential to the intended application of the product. Performance Requirement characteristics are normally verifiable by following the Performance Check procedure in the 495/P Service Manual, Volume 1.
•
The Supplemental Information column provides more explanation about
related Performance Requirements, or describes typical performance for
characteristics not ordinarily verified by the Performance Check procedure.
The instrument performs an internal processor system check each time
power is turned on. The Functional or Operational Check procedure is
provided in Section 5, Instrument Check Out. This procedure will satisfy most
incoming inspections and will help familiarize you with the instrument capabilities. It does not require external test equipment or technical expertise.
Verification of Tolerance Values
Perform compliance tests of specified limits, listed in the Performance Requirement column, only after a 30-minute warm-up time (except as noted)
and after doing the front-panel CAL procedure. Use measurement instruments that do not affect the values measured. Measurement tolerance of
test equipment should be negligible when compared to the specified tolerance. When the tolerance of test equipment is not negligible, the error of the
measuring device should be added to the specified tolerance.
495 & 495P User Manual
2-1
Specification
Tabie 2-1: Frequency Related Characteristics
Characteristic
Performance Requirement
Supplemental Information
Center/Marker Frequency
Range
100 Hz to 1.8 GHz.
Tuned by the CENTER/MARKER
FREQUENCY control or the DATA
ENTRY push buttons.
Drift
With constant ambient temperature
and fixed center frequency.
After 30 minute warmup
SPAN/DIV >200 kHz
(1stl_O Unlocked)
Typically <25 kHz per minute.
SPAN/DIV < 200 kHz
Typically < 150 Hz per minute.
(1stl_O Locked)
After 1 hour warmup
SPAN/DIV >200 kHz
Typically < 5 kHz per minute.
(1stLO Unlocked)
Not significant when compared to
residual FM per minute of sweep
time.
SPAN/DIV < 200 kHz
(1stl_O Locked)
<50 Hz per minute
Readout Resolution
Initial Accuracy
At least 10% of SPAN/DIV.
±[20%D + (CF x REF) + 15 kHz]
where:
SPAN/DIV >200 kHz
(1stLO Unlocked)
SPAN/DIV < 200 kHz
(1stLO Locked)
Correction will occur at the end of
sweep for sweep times > 5 s/div.
Allow a settling time of one second
for each GHz change in CF.
D=SPAN/DIV or RESOLUTION
BANDWIDTH, whichever is greater
CF=Center Frequency
REF=Reference Frequency Error
±[20%D + (CF x REF) + 15 Hz]
where:
D=SPAN/DIV or RESOLUTION
BANDWIDTH, whichever is greater
CF=Center Frequency
REF=Reference Frequency Error
2-2
Specification
Specification
Table 2-1: Frequency Related Characteristics (Cont.)
Characteristic
Performance Requirement
Supplemental Information
Reference Frequency Error
Aging Rate
Short Term
<1 x 10~9/Day.
First 6 months
< 1 x 10~7 in first 6 months.
x 10~7/Year.
After first 6 months
Accuracy During Warmup at
+25° C 30 Minutes After
Power Up
Within 5 x 10~8 of the frequency
after 24 hours.
Temperature Sensitivity
Within 2 x 10~8 over the instrument operating temperature range
of -15° C to +55° C (referenced
to +25° C).
<1 x 10~7
+20° Cto +30° C temperature
range. 100 MHz CAL OUT Reference.
Accuracy
(After 30 Minute Warmup)
± [Counter frequency x Reference
frequency error) + 5 Hz + 1 LSD]
Count at center, marker, or A markers.
Sensitivity
Signal level, at center screen or at
marker, must be 20 dB or more
above the average noise level and
within 60 dB of the reference level.
Setability
Signal Counter
Readout Resolution
1 Hz to 100 MHz in decade steps,
selectable with COUNT RESOLUTION menu.
Residual FM
SPAN/DIV >200 kHz
Short term, after 1 hour warmup.
< 7 kHz total excursion in 20 ms
(1stLO Unlocked)
SPAN/DIV < 200 kHz
<5 Hz total excursion in 20 ms
(1stLO Locked)
Static Resolution Bandwidth
(6 dB down)
Within 20% of selected bandwidth
for all but the 1 0 Hz filter
Shape Factor (60 dB/6 dB)
7.5:1 or less for all but the 10 Hz
filter
60 dB Bandwidth for the 10 Hz
Filter
< 150 Hz
Line-related Sidebands
< -55 dBc (47 to 440 Hz)
495 & 495P User Manual
10 Hz to 1 MHz in decade steps,
and 3 M Hz.
2-3
Specification
Table 2-1: Frequency Related Characteristics (Cont.)
Characteristic
Performance Requirement
Noise Sidebands
< -70 dBc at 30X the selected
bandwidth for resolution bandwidths of 10 Hz and 100 Hz
< -75 dBc at 30X the selected
bandwidth for all other resolution
bandwidths
Video Filter
Pulse Stretcher Fall-Time
Supplemental Information
Normal
Wide
Narrow
3 MHz
1 MHz
100kHz
10kHz
1 kHz
100 Hz
10 Hz
30kHz
3kHz
3kHz
300 Hz
30 Hz
3 Hz
0.3 Hz
0.3 Hz
30kHz
3kHz
300 Hz
30 Hz
3 Hz
3 Hz
30 us/div of pulse amplitude
(typical).
Frequency Span/Div
Range
10 Hz/divto 100 MHz/div (in a
1 -2-5 sequence with the SPAN/
DIV control), or 10 Hz/div to
170 MHz/div (from the DATA
ENTRY push buttons) to two significant digits.
In addition, MAX SPAN provides a
full-band display, and ZERO SPAN
provides a 0 Hz display. With
ZERO SPAN, the horizontal axis is
calibrated in Time/div instead of
Frequency/div.
Accuracy/Linearity
2-4
Span/Div >50Hz
Within 5% of the selected Span/div
Span/Div <50 Hz
Within 10% of the selected Span/
div
Measured over the center 8 divisions
Specification
Specification
Table 2-1: Frequency Related Characteristics (Cont.)
Characteristic
Performance Requirement
Marker(s)
Supplemental Information
When activated, the marker is a
bright dot positioned by the CENTER/MARKER FREQUENCY control or the DATA ENTRY push buttons.
Normal Accuracy/Resolution
Identical to Center Frequency accuracy
For the active trace.
A MKR Accuracy
±1%of the total span
For the active trace. AMKR activates a second marker at the position of the single marker on the
trace. Parentheses appear on the
marker display line indicating that
the delta mode is active. The display shows the difference in frequency and amplitude. MKR 1«*2
selects which marker is tuned.
A MKR Resolution
495 & 495P User Manual
< 10% of Span/Div.
2-5
Specification
Table 2-2: Amplitude Related Characteristics
Characteristic
Vertical Display Modes
Performance Requirement
Supplemental Information
10 dB/div, 2 dB/div, and Linear.
Any integer between 1 to 15 dB/div
can also be selected via the DATA
ENTRY Keypad.
Reference Level
(Top of the graticule)
Range
Log Mode
From -117 dBm to +50 dBm with
no reference offset; +50 dBm includes 20 dB of IF gain reduction
(+30 dBm is the maximum safe
input).
Alternate reference levels are:
•
dBV (-130 dBVto +37 dBV)
•
dBmV (-70 dBmV to
+97 dBmV)
• dBuV(-10dBuVto
+ 157dBuV)
Linear Mode
39.6 nV/div to 2.8 V/div (1 W or
10 Vpeak maximum safe input).
Steps
10dB/DivMode
10 dB for the coarse mode.
1 dB for the FINE mode.
2 dB/Div Mode
1 dB for the coarse mode.
0.25 dB for the FINE mode.
LIN Mode
1 -2-5 sequence for coarse
mode.
1 dB equivalent steps for FINE
mode.
Set via DATA ENTRY
Steps correspond to the display
mode in coarse, except for 2 dB/
div where steps are 1 dB.
In FINE mode:
• 1 dB when the mode is 5 dB/
div or more.
• 0.25 dB for display modes of
4 dB/div or less (referred to as
AAmode).
Keypad
2-6
Specification
Specification
Table 2-2: Amplitude Related Characteristics (Cont.)
Characteristic
Performance Requirement
Supplemental Information
Marker(s) Accuracy
Identical to REF LEVEL accuracy
plus cumulative error of display
scale. (Dependent on vertical position.)
Frequency Response and
Display Flatness
Frequency response is measured
with 10 dB of RF attenuation.
About the mid-point between
two extremes
±1.0 dB
Accuracy
Response is affected by:
• InputVSWR
• Gain variation
•
Mixer conversion
Dependent on the following characteristics:
• RF Attenuation Accuracy
• IF Gain Accuracy
• Resolution Bandwidth
• Display Mode
• Calibrator Accuracy
• Frequency Response
• [Blue-SHIFT] [CAL] routine
reduces error between resolution bandwidths at -20 dBm
REF LEVEL. Other REF LEVELs may have larger errors.
• Ambient Temperature Change
(±0.15 dB/° C maximum, typically ±0.05 dB/° C)
Display Dynamic Range
90 dB maximum for Log Modes
>12dB.
8 divisions for Linear Mode.
Accuracy
10dB/divMode
±1.0 dB/10 dB to a maximum cumulative error of ±2.0 dB over
80 dB range
2 dB/div Mode
±0.4 dB/2 dB to a maximum cumulative error of ±1.0 dB over
16 dB range
LIN Mode
±5% of full scale
495 & 495P User Manual
Maximum cumulative error of
±4.0 dB over 90 dB range.
2-7
Specification
Table 2-2: Amplitude Related Characteristics (Cont.)
Characteristic
Performance Requirement
Supplemental Information
RF Attenuator
0-60 dB in 10 dB steps.
Range
Accuracy DC to 1800 MHz
Within 0.5 dB/10 dB to a maximum
of 1 dB over the 60 dB range
Gain Variation Between Resolution
Bandwidths
Measured conditions:
•
Measured at -20 dBm
• MIN DISTORTION mode
• After CAL routine @ 25° C
With Respect to 3 MHz Filter
<±0.4dB
Between Any Two Filters
<0.8dB
IF Gain
Range
87 dB of gain increase, 20 dB of
gain decrease (MIN NOISE and
REDUCED GAIN modes activated),
in 10dBand 1 dB steps.
Accuracy
1 dB Step
< 0.2 dB/dB step to 0.5 dB/9 dB
steps except at the decade transitions
2-8
Decade Transitions
-19 to -20 dBm
-29 to -30 dBm
-39 to -40 dBm
-49 to -50 dBm
-59 to -60 dBm
0.5 dB or less
Maximum Deviation Over the
Range
±2dB
Maximum 1 dB cumulative error
over 10dB.
Specification
Specification
Table 2-2: Amplitude Related Characteristics (Cont.)
Characteristic
Performance Requirement
Differential Amplitude
Measurement
Supplemental Information
AA mode provides differential measurements in 0.25 dB increments.
(This is not related to the AMKR
mode.)
Maximum range of 57.75 dB dependent on Reference Level when
the AA mode was activated.
Range
Accuracy
Typical sensitivity 1 00 Hz to 1 kHz
is -75 dBm at 10 Hz Resolution
Bandwidth.
Equivalent maximum input noise
for each resolution bandwidth.
Measured at 25° C with:
• 0 dB RF attenuation (Min Atten
OdB)
• Narrow Video Filter On
• Vertical Display 2 dB/div (5 dB/
divinlOHzRBW)
• Digital Storage On
• Max Hold Off
• Peak/Average in Average
• 1 sec Time/Div
• Zero Span
• Input Terminated in 50 O
Spurious Responses
Residual
- 1 00 dBm or less
With no input signal.
-70 dBm or less
From any two on-screen signals
within any frequency span.
In MIN DISTORTION mode.
Harmonic Distortion
-60 dBc or less
Measured across the entire band,
with -30 dBm input and 0 dB attenuation.
LO Emission
-70 dBm or less
With 0 dB RF Attenuation.
3rd Order Intermediation Products
"Option 07 only. "Above 5 MHz. "Above 10 MHz.
495 & 495P User Manual
2-9
Specification
Table 2-3: Input Signal Characteristics
Characteristic
Performance Requirement
Supplemental Information
Type N female connector. (See Option 07 characteristics at the end of
this section for supplemental specifications concerning an additional
75 Q input.)
RF INPUT
Impedance
50 Q.
VSWRwith >10dB
1.3:1 maximum (typically 1.2:1).
RF Attenuation
VSWR with 0 dB
RF Attenuation
2.0:1 maximum (typically 1.9:1).
Maximum Safe Input
(With 0 dB RF Attenuation)
1 dB Compression Point
(Minimum)
+30 dBm (1 W) continuous or
75 W peak, pulse width of 1 us or
less with a maximum duty factor of
0.001 (attenuator limited).
0 dBm
Measured in MIN NOISE mode
with no RF Attenuation.
EXT REF IN
Frequency
1 , 2, 5, or 10 MHz ±5 PPM
Power
- 1 5 dBm to + 1 5 dBm
Waveshape
Sinewave, ECL, or TTL, with a duty
cycle of 40%-60%.
Input Impedance
AC=50 Q, DC=500 Q.
HORIZ | TRIG (rear panel)
DC coupled input for external horizontal drive (selected by the EXT
position of the TIME/DIV control)
and AC coupled input for external
trigger signals (selected at other
positions of the TIME/DIV control).
Sweep Input Voltage Range
0 to +10 V (DC + Peak AC) for fullscreen deflection.
Trigger Input Voltage Range
Minimum
At least 1.0 Vp_p from 15 Hz to
500 kHz
Typically 1 MHz at 1.5 Vpeak.
Maximum
DC + Peak AC
50V.
AC
30 VRMS to 10 kHz, then derate linearly to 3.5 VRMS at 100 kHz and
above.
Pulse Width
2-10
0.1 |JS minimum.
Specification
Specification
Table 2-3: Input Signal Characteristics (Cont.)
Characteristic
MARKER | VIDEO (rear panel)
Performance Requirement
Supplemental Information
External Video input or External
Video Marker input, switched by
pin 1 of the ACCESSORIES connector.
VIDEO Input Level
0 to +4 V for full-screen display
with pin 1 of the ACCESSORIES
connector low.
MARKER Input Level
0 to-10V.
Interfaces with TEKTRONIX 1405
TV Sideband Adapter.
ACCESSORY Connector (J104)
Pin1
25-pin connector (not RS-232 compatible).
Provides bi-directional access to
the instrument bus. Also provides
External Video select. All lines are
TTL compatible.
Maximum voltage on all lines is
±15 V.
External Video Select.
Low selects External VIDEO Input.
High (default) selects Video
MARKER Input.
Pin 2
Not used.
Pin 3
Not used.
Pin 4
Internal Control.
High (default) selects internal control. Instrument bus lines are output at the ACCESSORIES connector.
Low selects External control.
Instrument bus lines at the ACCESSORIES connector accept
input from an external controller.
Pin 5
Chassis Ground.
Pins6-13a
Instrument Bus Address Lines 7-0.
Pin 14a
Instrument Bus Data Valid signal.
Pin 15a
Instrument Bus Service Request
signal.
Pin 16a
Instrument Bus Poll signal.
•Output when Internally controlled (pin 4 high) and Input when externally controlled (pin 4 low).
495 & 495P User Manual
2-11
Specification
Table 2-3: Input Signal Characteristics (Cont.)
Characteristic
Performance Requirement
Supplemental Information
Pin 17
Data Bus Enable input signal for
external controller.
High (unasserted) disables external data bus.
Low enables external data bus.
Pins 18-25a
Instrument Bus Data lines 0-7.
Active when External Data Bus Enable (pin 17) is low.
"Output when internally controlled (pin 4 high) and input when externally controlled (pin 4 low).
Table 2-4: Output Signal Characteristics
Characteristic
Performance Requirement
Supplemental Information
Calibrator (CAL OUT)
-20 dBm ±0.3 dB at 100 MHz
100 MHz (phase locked to reference oscillator).
1st LO and 2nd LO OUTPUTS
Provide access to the output of the
respective local oscillators.
These ports must be terminated in
50 n at all times.
1stl_O OUTPUT Power
+6 dBm to +20 dBm.
2nd LO OUTPUT Power
-10 dBm to+15 dBm.
VERT Output
Provides 0.5 V ±5% (open circuit)
of signal per division of video that
is above and below the center line.
Full range is -2.0 V to +2.0 V.
250 mV maximum ripple. Source
impedance is approximately 1 kQ.
HORIZ Output
Provides 0.5 V/div (open circuit)
either side of center. Full range
-2.5 V to +2.5 V. Source impedance is approximately 1 kQ.
PEN LIFT
TTL compatible, nominal +5 Vto
lift plotter pen.
10 MHz IF output
Output level is approximately
-5 dBm for a full-screen signal at
-30 dBm reference level. Nominal
impedance is approximately 50 Q
2-12
Specification
Specification
Table 2-4: Output Signal Characteristics (Cont.)
Performance Requirement
Characteristic
Supplemental Information
In accordance with IEEE 488-78
standard and Tektronix Codes and
Formats standard (version 81.1).
IEEE STD 488 PORT
P-Version
Implemented as SH1, AH1, T5, L3,
SR1, RL1, PP1, DC1, DT1, and CO.
Non-P Version (Plotter Output)
Implemented as SH1, AHO, T3, LO,
SRO, RLO, PPO, DCO, DTO, and CO.
PROBE POWER (rear panel)
Provides operating voltages for active probes.
Outputs
Pin1
+5 Vat 100 mA maximum.
Pin 2
Ground.
Pin 3
-15V at 100 mA maximum.
Pin 4
+15 V at 100 mA maximum.
All inputs and outputs are listed in
Table 2-3, Input Signal Characteristics.
ACCESSORIES (J104)
Table 2-5: General Characteristics
Characteristic
Performance Requirement
Sweep
Supplemental Information
Triggered, auto, manual , single
sweep, and external.
Sweep Time
20 us/div to 5 s/div in 1 -2-5 sequence (10 s/div available in
AUTO)
Accuracy
±5% over center 8 divisions
Triggering
INTERNAL, EXTERNAL, FREE
RUN, and LINE.
Internal Trigger Level
2 divisions or more of signal
EXTERNAL Trigger Input Level
1.0 Vp.p minimum
EXTERNAL is AC-coupled (15 Hz
to 500 kHz). Maximum external
trigger input is 50 V (DC + Peak
AC).
CRT Readout
495 & 495P User Manual
Displays all parameters listed on
the CRT bezel, plus operating messages.
2-73
Specification
Table 2-5: General Characteristics (Cont.)
Characteristic
Performance Requirement
Battery-Powered Memory
Supplemental Information
Instrument settings, macros, displays, and calibration offsets are
stored in battery-powered non-volatile RAM.
Battery Life
1 -2 years.
At +55° C
Ambient Temperature
At +25° C
Ambient Temperature
Lithium (Standard)
At least 5 years.
Silver (Option 39)
2-5 years.
Temperature Range for
Retaining Data
Operating
-15° C to+55° C.
Non-Operating
-30° Cto+85°C.
Table 2-6: Power Requirements
Characteristic
Performance Requirement
Supplemental Information
Line Frequency Range
47 to 440 Hz
Line Voltage Range
90 VAC to 132 VAC
115 V nominal.
180 VAC to 250 VAC
230 V nominal.
Line Fuse
115V Nominal
4A Fast-Blow
230 V Nominal
2A Slow-Blow
Input Power
210 W maximum (3.2 A)
At 115V and 60 Hz.
Leakage Current
2-74
47-63 Hz
3.5 mA maximum.
Else
5 mA maximum.
Specification
Specification
Table 2-7: Environmental Characteristics
Description
Characteristic
Meets MIL-T-28800C, type III class 3, style C specifications as follows:
Temperature
Operating
-15°Cto+55°C.
Non-Operating3
-62°Cto+85°C.
Humidity
Operating
95% (+5%, -0%) relative humidity.
Non-Operating
Five cycles (120 hours) in accordance with MILStd-810D, Procedure 3 (modified).
Altitude
Operating
15,000 feet, tested to 25,000 feet.
Non-Operating
40,000 feet, tested to 50,000 feet.
Vibration, Operating (instrument secured to a
vibration platform during test)
MIL-Std-810D, Method 514 Procedure I (modified). Resonant searches in all three axes from 5 Hz to 15 Hz at
0.060" displacement for 7 minutes, 15 Hz to 25 Hz at
0.040" displacement for 3 minutes, and 25 Hz to 55 Hz
at 0.020" displacement for 5 minutes (tested to 0.025").
Dwell for an additional 10 minutes in each axis at the
frequency of the major resonance or at 55 Hz if none
was found. Resonance is defined as twice the input
displacement. Total vibration time is 75 minutes.
Shock (Operating and Non-Operating)
Three guillotine-type shocks of 30 g, one-half sine,
11 ms duration each direction along each major axis;
total of 18 shocks. Tested to 50 g.
Transit Drop (free fall)
8 inch, one per each of six faces and eight corners
(instrument is tested and meets drop height of 12 inches).
Electromagnetic Interference (EMI)
Meets requirements described in MIL-Std-461B Part 4,
except as noted.
Conducted Emissions
Test Method
Remarks
CE01-60Hzto15kHz
1 kHz to 15 kHz only
CE03-15kHzto50MHz
15 kHz to 50 kHz, relaxed
by 15 dB
power leads
•After storage at temperatures below -15° C, the instrument may not reset when power is first turned on. If this happens, allow the
instrument to warm up for at least 15 minutes, then turn POWER OFF for 5 seconds and back ON.
495 & 495P User Manual
2-15
Specification
Table 2-7: Environmental Characteristics (Cont.)
Characteristic
Description
Conducted Susceptibility
Test Method
Remarks
CS01 -30 Hz to 50 kHz
Full limits
power leads
Full limits
CS02-50 kHz to 400 MHz
power leads
Radiated Emissions
Radiated Susceptibility
CS06-spike power leads
Full limits
RE01 -30 Hz to 50 kHz
magnetic field
Relaxed by 10 dB for fundamental to 10th harmonic
of power line
Exceptioned, 30 kHz to
36kHz
RE02-14kHzto10GHz
Full limit
RS01 -30 Hz to 50 kHz
Full limit
RS02-Magnetic Induction
To 5 A only, 60 Hz
RS03-14 kHz to 10 GHz
Up to 1 GHz
Table 2-8: Physical Requirements
Characteristic
Description
Weight
42 Ibs 13 oz (19.3 kg) maximum.
Including cover and standard accessories, except
manuals.
See the Options Characteristics for alternate specifications.
Dimensions
Without Front Cover, Handle, or Feet
6.9 x 12.87 x 19.65 inches
(175 x327 x 499 mm).
With Front Cover, Feet, and Handle
Handle Folded Back Over the Instrument
9.15 x 15.05 x 23.1 inches
(232 x 382 x 587 mm).
Handle Fully Extended
9.15 x 15.05 x 28.85 inches
(232 x 382 x 732.8 mm).
2-76
Specification
Specification
2-78
Specification
This section describes spectrum analyzer unpacking, installation, power
requirements, storage information, and repackaging.
Unpacking and Initial
Inspection
Before unpacking the spectrum analyzer, inspect the shipping container for
signs of external damage. If the container is damaged, notify the carrier as
well as Tektronix, Inc. The shipping container contains the basic instrument
and its standard accessories. For a list of the standard accessories, refer to
Section 1, General Information. For ordering information, refer to the list
following the Replaceable Mechanical Parts list in the 495/P Service Manual, Volume 2.
If the contents of the shipping container are incomplete, if there is mechanical damage or defect, or if the instrument does not meet operational check
requirements, contact your local Tektronix Field Office or representative.
Keep the shipping container if the instrument is to be stored or shipped to
Tektronix for service or repair. Refer to Storage and Repackaging for Shipment later in this section.
Functional Check
The instrument was inspected both mechanically and electrically before
shipment, and it should be free of mechanical damage and meet or exceed
all electrical specifications. Section 5, Instrument Check Out contains procedures to check functional or operational performance. Perform the functional
check procedure to verify that the instrument is operating properly. This
check is intended to satisfy the requirements for most receiving or incoming
inspections. A detailed electrical performance verification procedure in the
495/P Service Manual, Volume 1 provides a check of all specified performance requirements, as listed in the Specification section.
Air Flow Considerations
The instrument can be operated in any position that allows air flow into the
bottom and out the rear of the instrument. Feet on the four corners allow
ample clearance even if the instrument is stacked with other instruments.
The air is drawn in by a fan through the bottom and expelled out the back.
Avoid locating the instrument where paper, plastic, or any other material
might block the air intake.
495 & 495P User Manual
3-1
Preparation for Use
Front Cover and Accessories Pouch
The front cover provides a dust-tight seal and a convenient place to store
accessories. Use the cover to protect the front panel when storing or transporting the instrument. To remove the cover, stand the instrument on the two
back feet so the name on the handle is facing up and towards you. Pull
slightly out and up on the sides of the cover.
Attached to the inside of the cover is the accessories pouch. To open the
accessories pouch, pull up evenly on the flap.
Handle Position
You can position the handle of the spectrum analyzer at several angles to
serve as a tilt stand. To stack instruments, position the handle at the top rear
of the instrument. To change the handle position, press in at both pivot
points and rotate the handle to the desired position.
WARNING
Removing or replacing the cabinet on the instrument can be hazardous. Only qualified service personnel should attempt to remove
the instrument cabinet.
Rack Adapter Kit
A field-installation kit is available to permit the spectrum analyzer to be rack
mounted in a standard 19-inch-wide rack on a non-tilting slide-out track. We
recommend fan-forced ventilation of the rack enclosure. If the rack-adapter
assembly is installed in an enclosed rack, a minimum depth of 25 inches
behind the front panel is recommended for proper air circulation. The rack
adapter kit comes complete with the slide-out tracks and all necessary
mounting hardware. Contact your local Tektronix Field Office or representative for additional information and ordering instructions.
Power Requirements
WARNING
Changing the power input can be dangerous.
Work safely
Know the intended power source
Set the instrument for the power source
Check the fuse for proper ratings
Use the power cord and plug intended for the power source
3-2
Preparation for Use
Preparation for Use
The 495/P operates from a single-phase power source that has one of its
current-carrying conductors (neutral) at ground (earth) potential. Do not
operate the 495/P from power sources where both current-carrying conductors are isolated or above ground potential (such as phase-to-phase on a
multi-phase system or across the legs of a 110-220 V single-phase, threewire system). In this method of operation, only the line conductor has over-
current (fuse) protection within the unit. Refer to the Safety Summary at the
front of this manual.
The AC power connector is a three-wire, polarized plug with the ground
(earth) lead connected directly to the instrument frame to provide electrical
shock protection. If the unit is connected to any other power source, connect the unit frame to an earth ground.
WARNING
Do not attempt to change the power input requirements. Unfamiliarity with safety procedures can result in personal injury. Refer all
power input changes to qualified service personnel. Refer to the
Safety Summary at the front of this manual.
Operate the spectrum analyzer from either 115 VAC or 230 VAC nominal line
voltage with a range of 90 to 132 or 180 to 250 VAC, at 48 to 440 Hz. Power
and voltage requirements are printed on a back-panel plate mounted below
the power input jack. Refer power input changes to qualified service personnel. The 495/495P Service Volume 1 contains instructions to change the
input voltage range.
The international power cord and plug configurations are shown in Section 7, Options.
Short Term (less than 90 days)
For short term storage, store the instrument in an environment that meets
the non-operating environmental specifications in Section 2 of this manual.
Long Term
For instrument storage of more than 90 days, retain the shipping container
to repackage the instrument. The battery in the instrument does not require
removal. Package the instrument in a vapor barrier bag with a drying agent
and store in a location that meets the non-operating environmental specifications in Section 2 of this manual.
If you have any questions, contact your local Tektronix Field Office or representative.
495 & 495P User Manual
3-3
Preparation for Use
Repackaging for
Shipment
When the spectrum analyzer is to be shipped to a Tektronix Service Center
for service or repair, please attach a tag that provides the following information:
•
Owner's name and address
•
The name of the individual at your firm who can be contacted
•
Complete instrument serial number
•
Description of the service required.
If the original package is unfit for use or not available, use the following
repackaging information:
1. To allow for cushioning, use a corrugated cardboard container with a
test strength of 375 pounds (140 kilograms) and inside dimensions that
are at least six inches more than the equipment dimensions (refer to
Physical Characteristics in Section 2).
2. Install the instrument front cover, and surround the instrument with
plastic sheeting to protect the finish.
3. Cushion the 495/P on all sides with packing material or plastic foam.
4. Seal the container with shipping tape or a heavy-duty, industrial stapler.
Transit Case
A high-impact, ruggedized transit case is recommended if you require your
spectrum analyzer to be frequently shipped between sites. A hard transit
case that meets these requirements and has space to hold the instrument's
standard accessories is provided as an optional accessory for the spectrum
analyzer. Contact your local Tektronix representative for additional information and ordering assistance.
3-4
Preparation for Use
1
//// Controls,^ Connectors and Indicators
This section includes the descriptions of the instrument's main operating
modes. It also covers the functions of the controls, selectors, indicators, and
connectors for the 495/R which are all shown and identified in Figures 4-1
through 4-3 and 4-11 through 4-16. Some of the functions are described in
greater detail in Section 5, Instrument Check Out.
Included with many of the descriptions are syntax diagrams that graphically
display the function. The ovals and circles indicate a literal element that
must be sent (i.e., push button pressed) exactly as shown. Boxes contain a
name for an element (for example, DATA ENTRY represents numbered push
buttons [0] through [9], units terminators, [.], and [BACKSPACE]). The
arrows that connect the elements of the syntax diagrams show the possible
paths through the diagram. Parallel paths mean that one, and only one, of
the paths must be followed. A path around an element or group of elements
indicates an optional skip. Arrows indicate the direction that must be followed (usually the flow is to the right; but, if an element may be repeated, an
arrow returns from the right to the left of the element).
The following examples illustrate basic syntax diagram structure.
When DATA ENTRY boxes are part of a command's syntax diagram, there
are numbers shown with the boxes. These numbers represent the valid
range available for that particular command.
Operating Modes
Initial Entry Functions (Black-Labels)
Most of the 495P operating modes are selected by a single push button
press or control turn; i.e., [FREE RUN], TIME/DIV, [PULSE STRETCHER],
[MAX HOLD], PEAK/AVERAGE. Generally, these selections are the same
with all Tektronix 49x-Series Spectrum Analyzers.
495 & 495P User Manual
4-7
Controls, Connectors, and Indicators
Multiple Push Button Sequence Functions
([SHIFT] push buttons)
[Blue-SHIFT] Functions —There are many general operating modes
and two marker operating modes selected with multiple push button presses. Press the [Blue-SHIFT] push button before selecting a blue-labeled
function; i.e., [PLOT], [STORE DISP], [CAL]. For many of these functions,
menu prompts appear on the screen to guide you.
[Green-SHIFT] Functions — Most of the operating modes selected with
[Green-SHIFT] multiple-push button presses are marker related. Press the
[Green-SHIFT] push button before selecting a green-labeled function such
as [ASSIGN 1], [PEAK FIND]. For many of these functions, menu prompts
appear on the CRT readout to guide you.
There are also additional marker functions that can be assigned to either
push button [ASSIGN 1] or [ASSIGN 2] and then selected in the same
manner as the labeled functions. The MARKER MENU also has additional
marker functions that can be selected directly from the menu.
Terminating Multiple Push Button Sequences
A [SHIFT] multiple-push button sequence can be terminated at any time.
Push either the [Blue-SHIFT] or [Green-SHIFT] push button once to stop
the sequence and return the 495/P to the previous activity.
DATA ENTRY Functions (Orange Labels)
Some operations require the entry of numerical data; for example, to set
frequency or enter a number to select a choice from a menu. This will be as
part of a multiple-push button sequence. The screen will prompt you when a
number is required. Numbers are entered with the orange-labeled DATA
ENTRY push buttons. Numerical data is entered first, with a units terminator
entered last; for example, [1] [0] [MHz] for 10 MHz or [2] [0] [-dBx] for
-20 dBm.
Correcting Numerical Entry Errors
Use the [BACKSPACE] push button to correct errors in numerical data that
have been entered with the orange-labeled DATA ENTRY push buttons.
Each push button press backs the cursor up one space, erasing the number
in that location. You can then enter the correct numerical data and end the
sequence with a units push button.
4-2
Controls, Connectors, and Indicators
Controls, Connectors, and Indicators
4
COUNT — When this push button is pressed, the signal at the dot
position is counted with up to 1 Hz resolution at any FREQUENCY
SPAN/DIV setting. The resolution is selected with [Blue-SHIFT]
[COUNT RESOLN]. The signal must be 20 dB or more above the
noise level and above a level that is 60 dB down from the REFERENCE LEVEL setting.
5
AF — This push button allows measurement of the frequency differences. When pressed (lit), the frequency readout goes to zero. The
readout now shows only the offset, or deviation, from this reference as
the CENTER FREQUENCY is changed. The resolution of the readout
will be the less accurate of either the current CENTER FREQUENCY
resolution or the CENTER FREQUENCY resolution when [AF] was
activated. Do not confuse this push button with [Green-SHIFT]
[A MKR], which is described later in this section under Marker Functions.
6
[Blue-SHIFT] COUNT RESOLN — This push button sequence
allows you to select the desired counter resolution with the DATA
ENTRY push buttons. Terminate with one of the unit ([GHz], [MHz],
[kHz], or [Hz]) push buttons. The counter resolution will be truncated
to the decade that is less than or equal to the selected resolution.
7
CENTER/MARKER FREQUENCY — This control tunes the center
frequency or marker, if selected. Tuning of center frequency is done in
0.1 division increments, regardless of the selected FREQUENCY
SPAN/DIV setting. For marker frequency, tuning is either O.OI, 0.033, or
0.1 division increments, depending on how fast the control is turned.
In MAX SPAN mode, the center frequency is fixed, and only the frequency dot is tuned. The tuning range in narrow spans is identical to
wide spans.
8
+STEP — When the instrument is in the Tune Center Frequency
mode ([TUNE CF/MKR] push button unlit), this push button increases
the CENTER FREQUENCY by steps. The step size is determined by
[Blue-SHIFT] [STEP ENTRY] or [Green-SHIFT] [STEP SIZE]. See
[+STEP] later in this section under Marker Functions for alternate
operation.
9
-STEP — When the instrument is in the Tune Center Frequency
mode ([TUNE CF/MKR] push button unlit), this push button increases
the CENTER FREQUENCY by steps. The step size is determined by
[Blue-SHIFT] [STEP ENTRY] or [Green-SHIFT] [STEP SIZE]. See
[-STEP] later in this section under Marker Functions for alternate
operation.
4-4
Controls, Connectors, and Indicators
Controls, Connectors, and Indicators
10
[Blue-SHIFT] FREQ — This push button sequence allows direct
entry of center or marker frequency to 1 Hz resolution (it will be displayed to 100 Hz) using the DATA ENTRY push buttons. If the center
frequency entered is not in the current frequency range, the nearest
frequency range that contains the frequency will be automatically
selected. The center frequency range that can be selected is 0 Hz to
1800 MHz. Values that are entered outside this range will be ignored.
Frequency digits that are entered from the DATA ENTRY push buttons
are terminated with one of the four unit push buttons ([GHz], [MHz],
[kHz], or [Hz]).
11
POWER — This push-push switch turns the main power supply ON
(green light on) and OFF (in=ON, out=OFF). When power is switched
off, the current instrument front-panel set-up is stored in memory
register 0 (see Using the Store and Recall Features in Section 5) so
this set-up can be easily recalled. Full RF Attenuation is switched in
when power is switched off to protect the 1st mixer from overload and
damage.
495 & 495P User Manual
4-5
Controls, Connectors, and Indicators
12
IDENT — The IDENT mode allows identification of unwanted, internally-generated mixing products, as is generally the case when power at
the input exceeds the reference level by >30 dB. This push button
causes every other trace to be displaced vertically. The 1st and 2nd
local oscillator frequencies shift so that real, or true, signals are not
displaced horizontally on alternate sweeps, while spurious signals can
be shifted. The FREQUENCY SPAN/DIV must be 50 kHz or less.
13
AUTO RESOLN — When this function is on, RESOLUTION
BANDWIDTH is automatically selected to maintain a calibrated display
for, if possible, the selected FREQUENCY SPAN/DIV, TIME/DIV, VIDEO
FILTER, and VERTICAL DISPLAY modes. When the TIME/DIV control
is in the AUTO position, RESOLUTION BANDWIDTH is selected as a
function of FREQUENCY SPAN/DIV only, and TIME/DIV is selected to
maintain a calibrated display at the highest sweep rate. The RESOLUTION BANDWIDTH control will not operate when AUTO RESOLN
mode is on (the message TO CHANGE RESOLUTION AUTO RESOLN
MUST BE OFF will appear on the screen).
4-6
Controls, Connectors, and Indicators
Controls, Connectors, and Indicators
14
FREQUENCY SPAN/DIV — This control selects the frequency span
swept by the instrument. The range of this control is 10 Hz/Div to
100 MHz/Div. The FREQUENCY SPAN/DIV setting is indicated by the
CRT readout. Selection is in a 1 -2-5 sequence plus MAX SPAN
mode and ZERO SPAN mode, or time domain. FREQUENCY SPAN/
DIV can also be entered with the [Blue-SHIFT] [SPAN/DIV] push
button sequence and the DATA ENTRY push buttons. The 495/P will
try to maintain a calibrated display if the TIME/DIV control is in the
AUTO position or the [AUTO RESOLN] push button is active (lit).
When the FREQUENCY SPAN/DIV is in the MAX SPAN mode, the full
band is displayed. A dot near the top of the screen indicates the
CENTER FREQUENCY readout position on the span. This dot and the
center frequency position will be center screen when the FREQUENCY
SPAN/DIV is reduced from the MAX SPAN position. When the markers
are on, they show the frequency position, and the dot goes to centerscreen.
When the FREQUENCY SPAN/DIV is set to ZERO SPAN mode, the
495/P operates like a tunable receiver. The 495/P displays signals
within the resolution bandwidth in the time domain, with the CRT
reading out TIME/DIV instead of FREQUENCY SPAN/DIV.
495 & 495P User Manual
15
RESOLUTION BANDWIDTH — This control selects the bandwidth of
the 495/P. Selected bandwidth is indicated on the CRT readout. The
bandwidth selections are 10 Hz, 100 Hz, 1 kHz, 10 kHz, 100 kHz,
1 MHz, and 3 MHz. TIME/DIV is automatically selected to match the
selected bandwidth when the TIME/DIV control is in the AUTO position.
16
[Blue-SHIFT] SPAN/DIV — This push button sequence allows direct
entry of FREQUENCY SPAN/DIV with two significant digits of resolution. The FREQUENCY SPAN/DIV range that can be selected is 10 Hz/
Divto 170 MHz/Div. If a value outside the allowable range is entered,
the FREQUENCY SPAN/DIV will switch to 10 Hz if the selected value is
less than 10 Hz, or to MAX SPAN mode if the selected value is greater
than 170 MHz. Spans entered from the DATA ENTRY push buttons are
terminated with one of the four unit push buttons ([GHz], [MHz],
[kHz], or [Hz]).
4-7
Controls, Connectors, and indicators
4-8
17
MAX SPAN — When activated, the 495/P sweeps the entire frequency
range. The position of the 495/P's CENTER FREQUENCY is shown
with a dot near the top of the screen. When this function is turned off,
the span returns to the previous FREQUENCY SPAN/DIV setting.
When the markers are on, they show the frequency position, and the
dot goes to center.
18
ZERO SPAN — This push button switches the span to zero for time
domain display. When ZERO SPAN mode is turned off, the FREQUENCY SPAN/DIV returns to its previous value.
19
UNCAL — This indicator lights when the display amplitude or frequency is no longer calibrated; e.g., the sweep rate is not compatible with
the FREQUENCY SPAN/DIV and RESOLUTION BANDWIDTH. Select a
slower sweep rate or larger RESOLUTION BANDWIDTH to return to
calibrated operation.
Controls, Connectors, and Indicators
Controls, Connectors, and Indicators
20
TUNE CF/MKR — When this push button is lit, a single marker appears on the trace of highest priority. The marker can be moved with
the CENTER/MARKER FREQUENCY control. When the push button
is pressed again, the marker remains and does not change its horizontal position. The CENTER/MARKER FREQUENCY control now
adjusts the center frequency.
21
[Blue-SHIFT] MKR OFF — This push button sequence turns the
marker(s) off.
22
[Green-SHIFT] 1*-MKR-»2 — This push button sequence alternate-
ly selects which marker will be tuned when [Green-SHIFT] [A MKR]
is on.
23
495 & 495P User Manual
+STEP — When the instrument is in the tune marker mode (the
[TUNE CF/MKR] push button is lit), this push button increases the
marker frequency by steps (this function is limited to the edge of the
screen when not on an active trace). The step size is determined by
[Green-SHIFT] [STEP SIZE] or [Blue-SHIFT] [STEP ENTRY]. See
[+STEP] earlier in this section under Frequency for alternate operation.
4-9
Controls, Connectors, and Indicators
24
25
-STEP — When the instrument is in the tune marker mode (the
[TUNE CF/MKR] push button is lit), this push button decreases the
marker frequency by steps (this function is limited to the edge of the
screen when not on an active trace). The step size is determined by
[Green-SHIFT] [STEP SIZE] or [Blue-SHIFT] [STEP ENTRY]. See
[-STEP] earlier in this section under Frequency tor alternate operation.
[Green-SHIFT] STEP SIZE — This push button sequence defines
the frequency step of the CENTER FREQUENCY, MARKER FREQUEN-
CY, or the DELTA MARKER FREQUENCY, whichever mode is active.
26
[Blue-SHIFT] MKR -» CENTER — This push button sequence
centers the signal at the active marker by setting the CENTER FREQUENCY equal to the MARKER FREQUENCY (this function is not
available with a stored trace).
4-70
27
[Green-SHIFT] dB/Hz — This push button sequence mathematically
figures the average noise power in a bandwidth at the current marker
position.
28
[Green-SHIFT] MKR -> REF LVL — This push button sequence
changes the reference level of the top graticule to the present marker
amplitude (this function is not available with a stored trace).
29
[Green-SHIFT] SIGNAL TRACK — This push button sequence
automatically maintains tuning of a drifting signal within limits. While
this mode is active, SIGNAL TRACK will be displayed on the screen.
SIGNAL TRACK IDLE will be displayed when there is no signal above
the threshold. Excessive drift will disable this function. Select SET
SIGNAL THRESHOLD from the MARKER Menu to set the threshold.
30
[Green-SHIFT] ASSIGN 2 — This push button sequence turns on
the assigned function.
31
[Green-SHIFT] ASSIGN 1 — This push button sequence turns on
the assigned function.
32
[Green-SHIFT] BANDWIDTH — This push button sequence places
markers on a selected signal and displays the X dB bandwidth (select
ENTER BANDWIDTH NUMBER from the marker menu to set X). The
screen will display NO SIGNAL — BW IDLE when there is no signal at
the marker that meets threshold and bandwidth parameters. Set the
parameters by selecting SET SIGNAL THRESHOLD and ENTER
BANDWIDTH NUMBER after calling up the MARKER Menu each time.
Controls, Connectors, and Indicators
Controls, Connectors, and Indicators
33
[Green-SHIFT] PEAK FIND — This push button sequence places
the Primary marker at the peak of the highest on-screen signal.
[Green-SHIFT] [PEAK FIND] locates the left-most peak (or the
center peak of a cluster), but it is not a signal processing command
with the built-in intelligence. Peak B would be selected from the cluster
in Figure 4-5A; peak A would be selected in Figure 4-5B because the
low point (B) would stop a search from continuing to the cluster (C).
34
[Green-SHIFT] MKR START STOP — This push button sequence
allows you to set the start and stop frequencies directly from the delta
marker position (this function is not available with a stored trace).
[Green-SHIFT] [A MKR] must be on for this function to operate.
35
MARKER MENU — This push button calls up a menu display on the
screen that allows selection of one of the available marker commands
that are not permanently assigned to a front-panel push button.
RIGHT NEXT — This moves the Primary marker to the next visible
signal higher than the present marker frequency. If there is no signal to
the right of the Primary marker that meets threshold and signal type
parameters, one of the following messages will be displayed on the
screen (depending on whether CW, PULSE, or SPURS has been
selected as the signal type):
NO CW TO THE RIGHT ABOVE THRESHOLD
NO PULSE TO THE RIGHT ABOVE THRESHOLD
NO SPUR TO THE RIGHT ABOVE THRESHOLD
Select SET SIGNAL THRESHOLD and SET SIGNAL TYPE from the
Marker Menu to set the parameters.
LEFT NEXT — This moves the Primary marker to the next visible
signal lower than the present marker frequency. If there is no signal to
the left of the Primary marker that meets threshold and signal type
parameters, one of the following messages will be displayed on the
screen (depending on whether CW, PULSE, or SPURS has been
selected as the signal type):
NO CW TO THE LEFT ABOVE THRESHOLD
NO PULSE TO THE LEFT ABOVE THRESHOLD
NO SPUR TO THE LEFT ABOVE THRESHOLD
Select SET SIGNAL THRESHOLD and SET SIGNAL TYPE from the
MARKER MENU to set the parameters.
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NEXT LOWER PEAK — This moves the Primary marker to the signal
with the next lower amplitude, either left or right of the present marker
position. If there is no signal lower than the Primary marker that meets
threshold and signal type parameters, one of the following messages
will be displayed on the screen (depending on whether CW, PULSE, or
SPURS has been selected as the signal type):
NO LOWER CW SIGNAL ABOVE THRESHOLD
NO LOWER PULSE SIGNAL ABOVE THRESHOLD
NO LOWER SPUR ABOVE THRESHOLD
Select SET SIGNAL THRESHOLD and SET SIGNAL TYPE from the
MARKER MENU to set the parameters.
NEXT HIGHER PEAK — This moves the Primary marker to the signal
with the next higher amplitude, either left or right of the present marker
position. If there is no signal higher than the Primary marker that
meets threshold and signal type parameters, one of the following
messages will be displayed on the screen (depending on whether CW,
PULSE, or SPURS has been selected as the signal type):
NO HIGHER CW SIGNAL ABOVE THRESHOLD
NO HIGHER PULSE SIGNAL ABOVE THRESHOLD
NO HIGHER SPUR ABOVE THRESHOLD
Select SET SIGNAL THRESHOLD and SET SIGNAL TYPE from the
MARKER MENU to set the parameters.
SET SIGNAL TYPE — This alters the marker functions to recognize
one of three signal types above the threshold (select SET SIGNAL
THRESHOLD from the MARKER MENU to set the threshold).
CW — Identifies continuous wave signals and ignores spurious
signals and impulses.
PULSE — Identifies the peak of pulsed RF lobes for either line
(lines must be <2 minor divisions apart) or dense spectra.
SPURS — Identifies all signals.
Figure 4-4 is a signal enlarged to show how the 495/P locates the
signal peak with one of the signal processing functions. The signal
processing functions are RIGHT NEXT, LEFT NEXT, NEXT LOWER
PEAK, NEXT HIGHER PEAK. The 495/P measures both the individual
left-most and right-most peaks of a signal. From this reading, the
495/P calculates the exact center of the signal. If this location is a
digital storage point, the marker is positioned here. If, as in Figure 4-4,
the calculated center of the signal is not equal to the maximum digital
storage point, the marker is positioned on the closest point to the
center. At the end of this section are five illustrations (Figure 4-6
through Figure 4-10) showing the use of this signal finding command.
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SET SIGNAL THRESHOLD — This changes the minimum visible
signal level for the marker functions of Right Next, Left Next, Next
Lower Peak, Next Higher Peak, Peak Find, Bandwidth Mode, and
Signal Track. Select AUTO to automatically set the threshold above the
noise floor.
ASSIGN FUNCTION TO KEY — This displays a menu (ASSIGN
Menu) of additional marker functions that can be assigned to either
the [Green-SHIFT] [ASSIGN 1] or [Green-SHIFT] [ASSIGN 2]
push buttons. Call up HELP mode for the assigned push button to get
a description of the assigned function. The function will remain assigned to the push button, even with power off, until another function
is assigned. The ASSIGN Menu accesses the following functions as
well as RIGHT NEXT, LEFT NEXT, NEXT LOWER PEAK, and NEXT
HIGHER PEAK, which are described under MARKER MENU.
MOVE RIGHT X dB — This allows you to select the number of dB
to move the Primary marker while staying on the trace (horizontal
movement to the right). If there is no level to the right of the Primary marker that meets threshold, the message NO POINT TO THE
RIGHT TO MOVE TO will be displayed on the screen.
MOVE LEFT X dB — This allows you to select the number of dB
to move the Primary marker while staying on the trace (horizontal
movement to the left). If there is no level to the left of the Primary
marker that meets threshold, the message NO POINT TO THE
LEFT TO MOVE TO will be displayed on the screen.
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Controls, Connectors, and Indicators
FIND PEAK AND CENTER —This places the active marker at the
peak of the highest on-screen signal (refer to the [Green-SHIFT]
[PEAK FIND] description later in this section). If a signal is present, the CENTER FREQUENCY is set equal to the marker frequency. This centers the signal of interest (this is useful when reducing
FREQUENCY SPAN/DIV by several settings at once). If there is no
signal above the threshold, the message NO POINT FOUND
ABOVE THE THRESHOLD will be displayed on the screen and the
marker will not move.
ENTER BANDWIDTH NUMBER —This sets the number of dB below
the signal peak at which bandwidth will be calculated when in the
marker BANDWIDTH mode. The number is stored in memory.
GREEN-SHIFT LOCK —This locks [Green-SHIFT] on so all greenlabeled functions can be directly selected. When GREEN-SHIFT
LOCK is on, the black-labeled functions associated with green-labeled
functions cannot be accessed. Blue-labeled functions operate normally. Press [Green-SHIFT] to exit this mode.
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Controls, Connectors, and Indicators
36
[Green-SHIFT] A MKR — This push button sequence is the on-off
switch for the Delta Marker mode. When activated, a second marker
appears at the position of the single marker on the trace. The symbols
() will appear on the screen on the marker frequency readout line to
indicate delta frequency and delta amplitude. To use Delta Marker,
press [TUNE CF/MKR] and set the marker to one point of interest on
the trace using the CENTER/MARKER FREQUENCY control. Press
[Green-SHIFT] [A MKR] to activate the Delta Marker Mode, and
move one of the markers to the second point of interest. Press
[Green-SHIFT] [A MKR] again to turn delta markers off.
Signal Finding
To the finding routine, a signal consists of a peak above threshold and two
points (one on each side of the peak) that are 3 dB below the peak. The
location of the signal is the highest amplitude point on the signal. Figures 4-6 through 4-10 illustrate the use of SET SIGNAL TYPE that can be
selected from the MARKER Menu. All of the figures use the signal processing function RIGHT NEXT. Any of the other signal processing functions
(LEFT NEXT, NEXT LOWER PEAK, NEXT HIGHER PEAK work in a similar
manner, according to their specific function. The minimum bandwidth criteria
for CW is defined as the two 3 dB down points that must be <5 kHz (1/2 a
RESOLUTION BANDWIDTH) apart.
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Controls, Connectors, and Indicators
Figures 4-6, 4-7, and 4-8 — If CW is selected, the 495/P will not identify
any signal because none of the signals displayed meets the minimum
bandwidth criteria. If PULSE is selected, the signals labeled D, E, and F
would be identified because the other signals in the display are less than 2
minor divisions apart. If the signals were greater than 2 minor divisions
apart, PULSE would identify all labeled signals (A, B, C, etc.). If SPURS is
selected, all signals would be identified (A, B, C, etc.).
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Figure 4-9 — The NEXT RIGHT function begins at the left screen margin.
With this display, all signals are identified by CW, PULSE, and SPURS
modes because the signals meet the minimum bandwidth criteria (i.e., the
selections would be A, B, C, D, and E).
Figure 4-10 — In this example, assume that the threshold is -70 dBm. If
CW is selected, signals B, E, F, and G would be identified. The other signals
do not meet the minimum bandwidth criteria, and would be ignored. If
PULSE is selected, signals A, B, D, E, F, and G would be identified. Signal C
would be skipped because it is located within 2 minor divisions of signal B.
The PULSE algorithm would not be able to identify signals B and C separately. If SPURS is selected, all signals would be identified.
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Controls, Connectors, and Indicators
37
POSITION T ^ — These screwdriver adjustments position the display along the horizontal and vertical axes. The [Blue-SHIFT] [CAL]
push button sequence will guide you through the adjustment of these
controls. Refer to [Blue-SHIFT] [CAL] for additional information.
38
VIDEO FILTER WIDE — This push button reduces video bandwidth
and high-frequency components for display noise averaging. The
video bandwidth selected is approximately 1/30th of the selected
RESOLUTION BANDWIDTH (1/100 for 3 MHz). Selecting [VIDEO
FILTER WIDE] cancels [VIDEO FILTER NARROW]. The filter value is
displayed in the lower readout.
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Controls, Connectors, and Indicators
Controls, Connectors, and Indicators
39
VIDEO FILTER NARROW — This push button reduces video
bandwidth and high-frequency components for display noise averaging. The video bandwidth selected is approximately 1/300th of the
selected RESOLUTION BANDWIDTH (1/30 for 10 Hz). Selecting [VIDEO FILTER NARROW] cancels [VIDEO FILTER WIDE]. The filter
value is displayed in the lower readout.
40
[Blue-SHIFT] REF LEVEL — This push button sequence allows
direct entry of reference level, with 1 dB resolution. The range is
+30 dBm to -117 dBm (+50 dBm if the MINIMUM NOISE and REDUCED GAIN modes are selected). Values entered outside this range
are ignored (values will be in the selected units; dBm, dBV, dBmV, or
dBuV). The [+dBx] or [-dBx] push buttons terminate the reference
level numbers entered.
41
[Blue-SHIFT] dB/DIV — This push button sequence allows direct
entry of the desired amplitude display factor. The range is 1 to 15 dB/
Div in 1 dB increments. Numbers outside the allowable range will be
ignored. Terminate the dB/div number entered with the [dB] push
button.
42
[Blue-SHIFT] CAL — This push button sequence starts a frequency
and reference level measurement procedure that uses the 495/P CAL
OUT signal. Messages on the screen guide the user through a procedure to adjust the Vertical and Horizontal POSITION, and LOG and
AMPL CAL front panel adjustments. The 495/P then runs an automat-
ic frequency, bandwidth, and relative amplitude measurement routine
for the resolution bandwidth filters.
The frequency measuring routine adjusts CENTER FREQUENCY. It
measures the frequency of each resolution bandwidth filter to reduce
CENTER FREQUENCY variation when changing RESOLUTION BAND-
WIDTH settings. The relative amplitude measuring routine reduces
REFERENCE LEVEL variation when changing RESOLUTION BANDWIDTH settings. To ensure that the 495/P meets frequency and amplitude performance characteristics, run these routines whenever the
instrument's surrounding temperature changes significantly. Cal
factors that are used internally to correct for the errors measured by
this function are retained in memory when the instrument power is off.
To display these factors, press [Blue-SHIFT] [LIN].
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Controls, Connectors, and Indicators
43
MIN RF ATTEN dB — This control specifies the lowest value of input
attenuation that will be used when REFERENCE LEVEL is selected.
This allows operator-control to protect the front end of the 495/P
against overload or damage from excessive signal level into the 1st
mixer. Actual attenuation is set according to the MIN RF ATTEN dB,
REFERENCE LEVEL, and [MIN NOISE/MIN DISTORTION] selections. It is displayed on the CRT readout. If the MIN RF ATTEN dB
setting is increased, the IF gain is automatically changed to maintain
the current REFERENCE LEVEL, if possible. The normal position is 0
to obtain the best noise level performance.
44
REFERENCE LEVEL — This control changes the reference level one
step for each stop. Automatic selection of the IF gain and RF Attenuation provide for the best overall noise and distortion performance. In
the LOG VERTICAL DISPLAY mode (FINE mode off), the step size
equals the selected dB/Div factor, except for 2 dB/Div, where step size
is 1 dB. When FINE mode is on, the step size is 1 dB for scale factors
of 5 dB/Div or more and 0.25 dB for VERTICAL DISPLAY factors of less
than 5 dB/Div. When the display factor is less than 5 dB/Div and FINE
mode is on, the Delta A mode is selected. Refer to Section 6, Operation for a description of the Delta A mode.
45
[Blue-SHIFT] REF LEVEL UNITS — This push button sequence
allows the selection of reference level units to be dBm, dBV, dBmV, or
dBuV.
46
AMPL CAL — This screwdriver adjustment, and the LOG CAL adjustment, calibrates the vertical portion of the display. AMPL CAL adjusts
the display amplitude. Press [Blue-SHIFT] [CAL] to initiate a procedure that will guide you through these adjustments. Refer to [BlueSHIFT] [CAL] for additional information.
47
LOG CAL — This screwdriver adjustment, and the AMPL CAL adjustment, calibrates the vertical portion of the display. LOG CAL adjusts
the logarithmic gain in dB/Div. Press [Blue-SHIFT] [CAL] to initiate a
procedure that will guide you through these adjustments. Refer to
[Blue-SHIFT] [CAL] for additional information.
48
MIN NOISE/MIN DISTORTION
MIN NOISE — (push button lit) — In this mode, the noise level is
reduced by changing the RF Attenuation and IF gain used for a particular reference level. Both are reduced 10 dB so noise generated in the
IF stages is decreased. However, intermodulation distortion products
will increase. RF Attenuation must be at least 10 dB for this control to
have any effect.
MIN DISTORTION — (push button not lit) — In this mode, intermodulation distortion products are minimized.
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Controls, Connectors, and Indicators
49
FINE (A A IN <5 dB/DIV) — This push button selects step size for the
REFERENCE LEVEL control. When FINE mode is off, the step size
equals the selected dB/Div factor, except for 2 dB/Div, where step size
is 1 dB. When FINE mode is on, the step size is 1 dB for scale factors
of 5 dB/Div or more and 0.25 dB for VERTICAL DISPLAY factors of less
than 5 dB/Div. When the display factor is less than 5 dB/Div and FINE
mode is on, the Delta A mode is selected.
In the Delta A mode the REFERENCE LEVEL readout goes to 0.00 dB,
and the REFERENCE LEVEL control steps in 0.25 dB increments.
These fine steps provide the means to make accurate relative amplitude measurements over a 48 dB measurement range. Refer to Delta
A mode operation in Section 6, Operation for more details.
50
PULSE STRETCHER — This push button causes the fall-time of pulse
signals to be increased so very narrow pulses can be seen. The effect
is most apparent for pulsed RF signals where pulse width is small
compared to one division of sweep time. Pulse stretcher operation
may be necessary for a digital storage display of such signals, to
ensure that the correct amplitude is displayed.
VERTICAL DISPLAY — These three push buttons select the vertical
display factors. The CRT readout indicates the selection. The vertical
display factor, in the LOG mode, can also be entered with the DATA
ENTRY push buttons.
51
LIN — With this push button activated, a linear display between zero
volts (bottom graticule line) and the reference level (top graticule line),
scaled in volts/division, is selected (see the REFERENCE LEVEL
description).
NOTE
The sequence [Blue-SHIFT] [UN] displays a list of the factors
used to internally correct for frequency and amplitude errors. The
factors shown are as measured with the last [Blue—SHIFT] [CAL]
operation. If one of the factors could not be measured at the last
operation, the old value will be noted. This means that the previously measured value is used. If [ or ] appears next to the amplitude
calibration factor, it means that this filter's amplitude related to the
3 MHz filter is outside the range of correction (correction is set to
the limit). Press [Blue-SHIFT] to exit this display.
495 & 495P User Manual
52
2 dB/DIV — This push button increases resolution so that each major
graticule division represents 2 dB. Display dynamic range is 16 dB.
53
10 dB/DIV — With this push button activated, the dynamic range of
the display is a calibrated 80 dB with each major graticule division
representing 10 dB.
'
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Controls, Connectors, and Indicators
TRIGGERING
54
TIME/DIV — This control selects sweep rates from 5 s/Div to 20 us/Div
in a 1 -2-5 sequence in addition to AUTO, MNL, and EXT sweep
modes.
AUTO — (automatic) — This position allows the sweep rate to be
selected automatically to maintain a calibrated display for most FREQUENCY SPAN/DIV, RESOLUTION BANDWIDTH, VIDEO FILTER, and
VERTICAL DISPLAY selections.
EXT — (external sweep) — This position allows the sweep circuit to be
driven by a signal applied to the rear-panel HORIZJTRIG (EXT IN)
connector. A voltage ramp of 0 to +10 V will sweep 10 divisions of
horizontal (X) axis.
MNL— (Manual) —This position allows the spectrum or display to be
manually swept with the MANUAL SCAN control.
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Controls, Connectors, and Indicators
495 & 495P User Manual
55
SINGLE SWEEP — When first pressed, this push button activates the
SINGLE-SWEEP mode and stops the current sweep. When pressed
again, the sweep trigger circuit is armed and the READY indicator is lit.
The sweep will run only after it receives a trigger signal. When SINGLE
SWEEP mode is selected, the TRIGGERING selection (i.e., FREE
RUN, INTernal, LINE, or EXTernal) is not changed. Select any TRIGGERING selection to cancel SINGLE SWEEP mode.
56
READY — (only used in the SINGLE SWEEP mode) — This indicator
lights when the trigger circuit is armed and ready for a trigger signal. It
remains lit until the sweep ends.
57
MANUAL SCAN — With TIME/DIV set to the MNL position, rotate this
control to manually scan the spectrum.
58
EXT — This push button allows the sweep to be triggered by signals
that are applied through the rear-panel HORIZJTRIG (EXT IN) connector. Other TRIGGERING selections are cancelled, including
SINGLE-SWEEP mode.
59
LINE — This push button allows a sample of the AC power line voltage to trigger the sweep. Other TRIGGERING selections are cancelled, including SINGLE-SWEEP mode.
60
INT — This push button allows the sweep to be triggered by any
signal at the left edge of the display that has an amplitude of 2.0 divisions or more. Other TRIGGERING selections are cancelled, including
SINGLE-SWEEP mode.
61
FREE RUN — This push button allows the sweep to free run without
regard to trigger source. Other TRIGGERING selections are cancelled,
including SINGLE-SWEEP mode.
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Controls, Connectors, and Indicators
Store/Recall
62
[Blue-SHIFT] STORE DISP — This push button sequence starts a
multiple-push button sequence that stores either the A or B waveform
and its associated readout and marker(s) in a numbered ([0] through
[8]) memory register. Information is held in memory while instrument
power is off. Messages displayed on the screen aid in completing the
multiple-push button sequence. After pressing [Blue-SHIFT]
[STORE DISP], a list of the stored displays is shown. Each stored
display is identified by its CENTER FREQUENCY. The number of digits
in a CENTER FREQUENCY in the menu list is an indication of the
FREQUENCY SPAN/DIV of that stored display (a larger number of
digits indicates a narrower span). This display includes a prompt
asking for the register number ([0] through [8]) into which the display
will be stored. Select the register from the DATA ENTRY push buttons.
When SAVE A mode is on, there is an operator prompt that asks
whether the A or B waveform is to be saved.
___________
__________
_________________
/—»< VIEW ~A~)—v
——»{ Blue SHIFT")—»{STORE DISP)—H DATA ENTRY o-s \-l
>——»•
^—»•( VIEW B )—'
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Controls, Connectors, and Indicators
Controls, Connectors, and Indicators
63
[Blue-SHIFT] RECALL — This push button sequence starts a multiple-push button sequence that recalls a selected waveform, with its
readout and marker(s) from one of the memory registers ([0] through
[8]). The waveform is placed in either the A or B display for viewing.
Information is held in memory while the instrument is off. After pressing [Blue-SHIFT] [STORE DISP], a list of the stored displays is
shown. Each stored display is identified by its CENTER FREQUENCY
This display includes a prompt asking for the register number ([0]
through [8]) from which the display will be recalled. Select the register
from the DATA ENTRY push buttons.
The readout for a recalled A waveform will only be displayed if VIEW B
and B-SAVE A modes are off and VIEW A mode is on. The readout
for a recalled B waveform will only be displayed if both VIEW B or
B-SAVE A modes are on and SINGLE SWEEP mode is selected. The
marker(s) will only be displayed if markers are turned on.
SAVE A mode is activated to allow the separate display of the A or B
waveform. Remember to turn on SINGLE SWEEP mode before recalling a waveform to B to prevent overwrite by the sweep. The waveform
cannot be recalled into B when in MANUAL or EXTERNAL sweep
modes. Press [Blue-SHIFT] to exit during the sequence.
Digital Storage — These push buttons allow either or both sections of
memory to be selected to provide digital storage. When [VIEW A] and
[VIEW B] are activated, contents of both the A and B memories are displayed on the screen. Both sections are updated with each sweep.
495 & 495P User Manual
64
B-SAVE A — When activated, the 495/P displays the difference
between the B waveform and the A waveform, and automatically turns
on SAVE A mode. The factory-set zero reference line is mid-screen.
Positive differences are displayed above this line and negative differences appear below the line. Refer any change in the position of the
zero reference line to authorized service personnel.
65
PEAK/AVERAGE — This control selects the vertical position (shown
on the screen by a horizontal line) at which digital storage switches
from peak detection to signal averaging. Signals displayed above the
cursor are peak detected. Signals displayed below the cursor are
digitally averaged.
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Controls, Connectors, and Indicators
66
MAX HOLD — This push button causes digital storage to retain the
maximum signal amplitude at every storage location (500 locations; or
1000 locations if SAVE A mode is off). If SAVE A mode is on, the A
waveform is not affected. Use [MAX HOLD] to measure frequency drift
or peak amplitude excursions of a signal.
67
SAVE A — This push button saves the A waveform and its readout.
The readout stored with the waveform is displayed if both [SAVE A]
and [VIEW A] are on, and [VIEW B] and [B-SAVE A] are off. If either
[VIEW B] or [B-SAVE A] is on, the readout reflects the current settings. Turning SAVE A mode off cancels B—SAVE A mode if it is on. If
SAVE A mode is off and either [VIEW A] or [VIEW B] is on, both
waveforms will be displayed. The A waveform is not updated by the
sweep if SAVE A mode is on.
68
VIEW B — This push button causes the B waveform to be displayed.
69
VIEW A — This push button causes the A waveform to be displayed. If
SAVE A mode is on and only the A waveform is being viewed, the CRT
readout will show the settings when the A waveform was stored.
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70
BACKSPACE — This push button backs the cursor up one space
each time it is pressed, erasing the number in that location. This
allows you to enter correct numerical data before finishing the sequence with a units push button.
495 & 495P User Manual
71
Green—SHIFT — This push button allows selection of the green-labeled front-panel push button functions. Press [Qreen-SHIFT] each
time before selecting a green-lettered function. [Green-SHIFT] also
cancels multiple push button sequence operations.
72
Blue-SHIFT — This push button allows selection of the blue-labeled
front-panel push button functions. Press [Blue-SHIFT] each time
before selecting a blue-lettered function. [Blue-SHIFT] also cancels
multiple push button sequence operations.
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Controls, Connectors, and Indicators
73
RECALL SETTINGS — This push button recalls an instrument frontpanel setup from memory. The screen displays the CENTER FREQUENCY of each stored setup as an aid in identifying the contents of
each register (0-9). The time and minimum RF Attenuation settings
stay at the knob values. Select the desired register number, and the
front-panel controls automatically switch to that setup. The instrument
settings are automatically stored in register 0 when the 495/P is turned
off, overwriting the settings previously stored there. To return to these
settings, press [RECALL SETTINGS] [0].
74
[Blue-SHIFT] STORE — This push button sequence allows a frontpanel setup to be stored in memory. Up to ten settings can be stored
in registers 0-9. The screen displays the CENTER FREQUENCY of
each setup as an aid in identifying the contents of each register. Select
the desired register, and the setup is stored. The instrument settings
are automatically stored in register 0 when the495/P is turned off,
overwriting the settings previously stored there.
75
[Blue-SHIFT] VIDEO FILTER WIDE — (Special Modes Menu; not
identified on the front panel) —This push button sequence brings up
a menu from which these special modes may be selected:
76
•
[0] Tracking Generator Mode
•
[1] Sideband Analyzer Mode
•
[2] Reduced Gain Mode
•
[3] EOS Corrections Mode
•
[4] Zero-Span Time Mode
PLOT — (495 Only) This push button causes display information to
directly drive a plotter. The plotters that can be driven include the
following:
•
Tektronix HC 100, 4662 Option 01, 4662 Option 31, or 4663 (emulating the 4662)
•
Hewlett Packard HP7470A, HP7475A, HP7580B, HP7585B, or
HP7486B
•
Gould 6310 or 6320
Press the [Blue-SHIFT] [SAVE A] push button sequence to select
the plotter type. Refer to Plotting the Display in Section 6 for details.
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Controls, Connectors, and Indicators
77
Units — The units GHz, MHz, kHz, Hz, +dBx, -dBx, and dB are
available to complete a number-entry function from the front panel.
78
[Blue-SHIFT] B-SAVE A — (Plot B-Save A Offset; not identified on
the front panel) —The vertical position of the zero reference line for
the B-SAVE A display is set with an internal switch selection. However, when using the [PLOT] function, the position of zero reference for
the plot must be entered using this function. The range for the position
is 0 to 255 with 125 representing center screen. Enter the position with
the DATA ENTRY push buttons when prompted by the CRT message,
and terminate with the [Hz] push button. The entered position is
stored in memory.
79
[Blue-SHIFT] SAVE A — (Select Plotter Type; not identified on the
front panel) —This push button sequence displays the list of the
plotter types available for use with the [PLOT] push button (495 only)
and [Blue-SHIFT] [PLOT] push button sequence (495Ponly). Select
the desired plotter type by choosing one of the menu items and entering the number on the DATA ENTRY push buttons. The choices are
listed below:
•
0=Tektronix 4662 Option 01 or the 4663 in a one-pen setup
•
1 =Tektronix 4662 Option 31 or the 4663 in a two-pen setup
•
•
2=HP7470A
3=Tektronix HC 100, HP7475A, HP7580B, HP7585B, or HP7586B,
Gould
Any plotter that is compatible with one of these can also be used. The
selected plotter type is stored in memory.
80
[Blue-SHIFT] MAX HOLD — (Instrument Errors; not identified on the
front panel) —This push button sequence displays all the detected
instrument errors; for use while troubleshooting.
81
DATA ENTRY — These orange push buttons are used to enter data
directly from the front panel when directed by a message on the CRT.
Numbers — The numbers [0] through [9] and a decimal point are
available to enter data from the front panel.
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82
[Blue-SHIFT] PULSE STRETCHER — (Diagnostic Aids; not identified on the front panel) — This push button sequence displays a menu
of all the available diagnostic aids for use while troubleshooting.
WARNING
MOST OF THE INFORMATION ACCESSED BY PRESSING THE
SEQUENCE [Blue-SHIFT] [PULSE STRETCHER] IS FOR QUALIFIED SERVICE PERSONNEL ONLY. UNFAMILIARITY WITH SAFETY
PROCEDURES CAN RESULT IN PERSONAL INJURY. PERFORM
ONLY THE OPERATIONS THAT CAN BE COMPLETED FROM THE
INSTRUMENT FRONT PANEL. DO NOT ATTEMPT TO REMOVE THE
INSTRUMENT PANELS OR PERFORM ANY INTERNAL OPERATIONS; CONTACT QUALIFIED SERVICE PERSONNEL.
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83
[Blue-SHIFT] RESET — This push button sequence resets all frontpanel settings to their original condition as if power was just turned on.
84
[Blue-SHIFT] RUN/STOP — This push button sequence has three
functions, depending on the status of macros.
•
If a macro is running, press [Blue-SHIFT] [RUN/STOP] to stop
the macro.
•
If a macro is stopped, press [Blue-SHIFT] [RUN/STOP] to
restart the macro.
•
If no macro is running or stopped, press [Blue-SHIFT] [RUN/
STOP] to run the last macro that was executed.
85
[Blue-SHIFT] MACRO MENU — This push button sequence selects
a macro to be executed. The title of the macro is displayed next to the
macro number.
86
[Blue-SHIFT] BASELINE CLIP — This push button sequence clips,
or blanks, about one graticule division of the spectrum trace at the
baseline of the display. Use BASELINE CLIP mode to observe the
readout at the bottom of the screen or to eliminate the bright baseline
when photographing displays.
87
[Blue-SHIFT] READOUT — This push button turns CRT readout on
and off. The brightness is proportional to the trace brightness. This
sequence does not affect prompt or help messages.
88
GRAT ILLUM — This push button switches the graticule lights from
dim for low-light viewing to bright for photographing displays.
Controls, Connectors, and Indicators
Controls, Connectors, and Indicators
89
HELP — This push button causes text to be displayed on the CRT to
explain the function of a selected front-panel control or push button.
Press the [HELP] push button; then press any push button or turn
most controls for an explanation of their function. Explanations are not
available for the PEAK/AVERAGE, INTENSITY, or MANUAL SCAN
controls. Press [HELP] again to exit this mode.
[Blue-SHIFT] HELP — This push button sequence allows selection
of all explanations for functions called out on the front panel in blue.
[Blue-SHIFT] [HELP] only needs to be pressed once to begin the
selection (i.e., [Blue-SHIFT] [HELP], [REF LEVEL], [PLOT],
[READOUT]). Press [HELP] again to exit this mode.
[Green-SHIFT] HELP — This push button sequence allows selection
of all explanations for functions called out on the front panel in green.
[Green-SHIFT] [HELP] only needs to be pressed once to begin the
selection (i.e., [Green-SHIFT] [HELP], [SIGNALTRACK], [PEAK
FIND], [MKR START STOP]). Press [HELP] again to exit this mode.
For additional information on HELP mode, see Using the HELP Feature
in Section 6.
90
495 & 495P User Manual
INTENSITY — This control adjusts the brightness of the CRT trace,
readout, and text. Beam focus is automatically controlled.
4-33
Controls, Connectors, and Indicators
4-34
91
RESET TO LOCAL/REMOTE — (495P Only) This push button is lit
when the 495P is in the remote state. While the instrument is remote,
the other front-panel controls are not active except for PEAK/AVERAGE, INTENSITY, and MANUAL SCAN. Indicators still reflect the
current state of front-panel functions. This push button is not lit when
the 495P is in the local state. While the 495P is under local control, no
GPIB messages are executed that would conflict with front-panel
controls or change the waveforms in digital storage. See Programming
Features in Section 6 for additional information.
92
[Blue-SHIFT] PLOT — (495P Only) This push button sequence
causes display information to be sent over the GPIB port to directly
drive a plotter. The plotters that can be driven are listed below:
•
Tektronix HC 100, 4662 Option 01, 4662 Option 31, or 4663 (emulating the 4662)
•
Hewlett Packard HP7470A, HP7475A, HP7580B, HP7585B, or
HP7486B
Controls, Connectors, and Indicators
Controls, Connectors, and Indicators
•
Gould 6310 or 6320
Press the push button sequence [Blue-SHIFT] to select the plotter
type. Refer to Plotting The Display in Section 6 for details. This push
button also causes the 495P to update the GPIB address.
93
[Green-SHIFT] SRQ — (495P Only) This push button sequence
sends a service request over the GPIB bus to the controller.
94
ADDRESSED — (495P Only) This indicator lights when the 495P is
addressed to either talk or listen. The characters T, L, and/or S appear
in the CRT readout to indicate talk, listen, and/or SRQ, respectively.
95
ZIA RF INPUT 50 Q - This 50 Q coaxial input connector is for RF
signals to 1.8 GHz. If the input signal has a DC component, use a
blocking capacitor in line with the signal.
The maximum, non-destructive input signal level to the input mixer
is +30 dBm or 1 W.
The maximum rating of the RF attenuator is +30 dBm (1 W average,
75 W peak pulse width 1 ms or less, with a duty cycle that does not
exceed 0.001). Burn-out occurs above 1 W. If MIN NOISE is activated and the RFATTEN is 60 dB, the +30 dBm rating will be
exceeded if the signal level is increased to a full-screen display.
Under these conditions the input level will be +40 dBm. Reduce
the level of high-powered signals with external attenuators.
Input signals to the mixer must not contain any DC component.
Refer to Signal Application in Section 6.
495 & 495P User Manual
96
ZJA RF INPUT 75 n — (Option 07 instruments only) — This connector provides calibrated 75 Q measurement capability.
97
OUTPUT (1ST LO/2ND LO) — These connectors are the outputs of
the respective local oscillators. The connectors must be terminated
into 50 Q when they are not connected to an external device.
4-35
Controls, Connectors, and Indicators
98
CAL OUT (Calibrator output) — This connector is the source of a
calibrated -20 dBm (±0.3 dB), 100 MHz signal and a comb of frequency markers 100 MHz apart. This 100 MHz source is the instrument reference frequency.
For Option 07 instruments using the 50 Q input, the signal is the same
as the standard instrument. The signal is +20 dBmV (±0.5 dB) when
using the 75 Q input.
99
4-36
Camera Power — This connector is the source of power for the
Tektronix cameras that have electrically-actuated shutters (either the
C-30BP Option 01 or the C-9 Option 07 is recommended). Singlesweep reset is not provided.
Controls, Connectors, and Indicators
Controls, Connectors, and Indicators
100 PROBE POWER — This connector provides operating power for
active probe systems. This connector should be used only with compatible probes or accessories specifically designed for use with this
power source.
495 & 495P User Manual
101
HORIZJTRIG (EXT IN) — Horizontal or triggering modes depend on
the TRIGGERING and TIME/DIV selections. In the EXTERNAL TRIGGERING mode, the connector is an AC coupled input for trigger
signals. Trigger amplitudes from 1.0 V to 50 Vp.p, with a 0.1 us minimum pulse width or within the frequency range of 15 Hz to 1 MHz, are
required for triggering. When the TIME/DIV selection is EXT, the
connector is a DC coupled input for horizontal sweep voltages. Deflection sensitivity is 1 V/Div. A 0 to +10 voltage will deflect the beam
across the screen from left to right.
102
MARKERJVIDEO (EXT IN) — (Available on instruments without
Option 42 only. See 110 MHz IF for Option 42 instruments.) This
connector interfaces the 495/P with a Tektronix 1405 TV Adapter to
display an externally-generated marker.
4-37
Controls, Connectors, and Indicators
In Option 42 instruments, the MARKER [VIDEO (EXT IN) port is
changed to 110 MHz IF. It provides a 110 MHz IF output with a
bandwidth greater than 4.5 MHz. External video signals used for
calibration may be injected into the PEN LIFT connector (see the PEN
LIFT description. This port is not compatible with a TV sideband
adapter.
103
HORIZ (OUTPUT) — This connector supplies a 0.5 V/Div horizontal
signal. Full range is -2.5 V to +2.5 V. Source impedance is approximately 1 kQ
104 VERT (OUTPUT) — This connector provides access to the video
signal with 0.5 V for each division of displayed video that is above and
below the center line. Source impedance is approximately 1 kQ.
NOTE
Both HORIZ and VERT output signals are driven from digital storage
if it is on. Both signals are driven from the 495/P sweep and video
amplifier stage if digital storage is off.
105 PEN LIFT (OUTPUT) — This connector provides access to a TTL
compatible signal to lift the pen of a chart recorder during 495/P
sweep retrace. This signal is always derived from the 495/P sweep,
regardless of the selection of the digital storage.
In Option 42 instruments, use this connector to input external video
signals if pin 1 of the ACCESSORIES connector is grounded (refer
any questions about this connection to qualified service personnel).
106
10 MHz IF (OUTPUT) — This connector provides access to the output
of the 10 MHz IF. The signal amplitude is about -30 dBm for a fullscreen display.
107 EXTREFIN (EXT IN) — A 50 O input for 1, 2, 5, or 10 MHz external
reference signals, within the -15 dBm to +15 dBm level. Phase noise
should be no greater than -110 dBc in a 1 Hz bandwidth at 10 Hz
offset, referenced to 10 MHz. The input signal must be a sinewave with
a duty cycle symmetry of 40% to 60%, ECL or TTL.
4-38
Controls, Connectors, and Indicators
Controls, Connectors, and Indicators
108 GPIB ADDRESS — (495P Only) These switches set the value of the
lower five bits of the instrument GPIB address. This value is the instrument's primary address. These switches also select the Talk Only and
Listen Only operating modes, and the message terminator for input
and output. Address 31 (11111) logically disconnects the 495P from
the bus. Address 0 (00000) is reserved for Tektronix 4050-Series
controllers. If these switches are changed after the instrument is
already active, press [RESET TO LOCAL] or [Blue-SHIFT] [PLOT]
to cause the 495P to read them again.
109 IEEE STD 488 PORT (GPIB) — This connector interfaces the 495 to
the selected plotter, and interfaces the 495P to the GPIB bus. The
interface functions provided in the 495 are SH1, AHO, T3, LO, SRO,
RLO, PPO, DCO, DTO, and CO. The interface functions provided in the
495P are SH1, AH1, T5, L3, SR1, RL1, PP1, DC1, DT1, and CO.
Details of how the switches are used in remote control are in the 495P
Programmer manual.
110 J104 ACCESSORY — This connector provides bi-directional access
to the instrument bus. It is not RS 232 compatible. A TTL 0 applied to
pin 1 selects EXTERNAL VIDEO. Video signals, which are applied to
rear-panel MARKER (VIDEO, are connected to the video path ahead
of the video filters.
495 & 495P User Manual
4-39
Controls, Connectors, and Indicators
4-40
Controls, Connectors, and Indicators
This section includes the basic instrument check-out procedures and preparation for first-time use. An operational check is included for the front-panel
push buttons and controls, and some of the operating functions. No extra
equipment is required to perform these check-out procedures, and the
instrument cabinet does not need to be removed. Refer any additional
instrument check out to qualified service personnel.
Firmware Version
Readout
When the instrument is first turned on, all of the front-panel LEDs will light
up. The front-panel processor firmware versions are then displayed on the
screen for approximately two seconds.
Error Message
Readout
There are error messages to report the following failure conditions:
•
Calibration failure
•
Power supply failure
•
Battery-operated RAM checksum error
Promptly report any error messages to qualified service personnel.
If the instrument detects an internal hardware failure, a failure report comes
on screen and remains for approximately 2 seconds. A status message then
appears and remains for as long as the failure exists. Press [HELP] to bring
error messages to the screen that explain the impact of the failure on instrument operation.
If you attempt to recall a display or setting from a location where nothing is
stored, you will get a checksum error message even though there is not
really an error. This need not be reported to service personnel.
Frequency
Corrections
If the oscillator frequency cannot be set due to a hardware failure, the instrument will attempt to set the oscillator frequency before each sweep. The
sweep holdoff time will increase with each try. To disable the oscillator
corrections, press [Blue-SHIFTJ [10 dB/DIV].
NOTE
Center frequency accuracy specifications will not be met in this
mode.
495 & 495P User Manual
5-7
Instrument Check Out
Press [Blue-SHIFT] [10 dB/DIV] again to enable the oscillator correction
routines. Another failure message will appear if the failure has not been
corrected.
Preparation for Use
^ne following procedure creates a display and calibrates center frequency
readout, display reference level, and bandwidth. Whenever a [SHIFT] push
button is required in this procedure to precede a multiple-push button
sequence, it is enclosed in brackets; i.e. [Blue—SHIFT].
Initial Turn On
1. Connect the spectrum analyzer power cord to an appropriate power
source (see Power Source and Power Requirements in Section 3 of this
manual) and push the [POWER] switch ON.
When [POWER] is switched ON (power-up), the processor runs a
memory and I/O test. If no processor system problems are found, the
power-up program will complete in approximately 7 seconds. The instrument is now ready to operate.
Figure 5-1 shows the normal CRT readouts following the 7-second
power-up period. If a problem does exist within the instrument, a message will appear on the screen. To bypass the failed test and attempt to
use the instrument, press the push button as directed in the error message. However, performance may not be as specified.
5-2
Instrument Check Out
Instrument Check Out
The 495/P operating functions and modes will initialize to the following
power-up states.
READOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ODBM
CENTER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 900MHZ
MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OMHZ
SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MAX
VERTICAL D I S P L A Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
RF ATTEN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20DB
FREQ RANGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0-1.8
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3MHZ
TRIGGERING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FREE RUN
AUTO RESOLN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
DIGITAL STORAGE . . . . . . . . . . . . . . . . . . . . . . VIEW A & VIEW B ON
MIN NOISE/MIN DISTORTION . . . . . . . . . . . . . . . . . . . . . . MIN NOISE
ALL OTHER PUSH BUTTONS . . . . . . . . . . . . . . . . INACTIVE OR OFF
2. Set the MIN RF ATTEN dB control to 0 (NORM) and the PEAK/AVERAGE control fully counterclockwise.
3. Set the TIME/DIV control to AUTO, REF LEVEL to -20 dBm, and adjust
the INTENSITY for the desired brightness. Note that the RF ATTEN
readout is now ODB.
495 & 495P User Manual
5-3
Instrument Check Out
4. Apply the CAL OUT signal to the RF INPUT through a 50 Q cable. A dot
marker appears in the upper portion of the screen in the MAX frequency
span/division mode. This marker indicates the location on the display to
which the 495/P frequency is tuned. With a frequency readout of OMHZ,
the marker is located in the top left portion of the screen.
5. Rotate the CENTER/MARKER FREQUENCY control and watch the dot
marker move across the display. Notice that the CENTER FREQUENCY
readout (top line) remains at 900 MHz, and the MARKER FREQUENCY
readout (second line) changes according to the position of the marker
(dot).
6. Harmonics of the 100 MHz CAL OUT signal will be displayed as shown
in Figure 5-2. To select 100 MHz center frequency, press the key sequence [Blue-SHIFT] [FREQ] [1] [0] [0] [MHz].
7. Press the push button sequence [Blue-SHIFT] [SPAN/DIV] [1] [0] [0]
[MHz] to change the SPAN/DIV to 100 MHz. The dot marker is now
horizontally centered, and the 100 MHz CAL OUT signal is at center
screen.
8. If a message appears on the screen, press [FINE] to continue the
calibration or [Blue-SHIFT] to exit the routine.
Display Calibration
When the [Blue-SHIFT] [CAL] push button sequence is pressed, the
instrument performs a center frequency and reference level calibration.
Prompts appear on the screen to guide the user through each procedure
step. The routine optimizes horizontal and vertical position, center frequency, reference level, and dynamic range.
This calibration should be done at regular intervals so the instrument can
meet its center frequency and reference level accuracy performance specifications. It should also be performed any time the instrument ambient temperature is substantially different from the last calibration. An explanation of
reference level accuracy with respect to ambient temperature is described in
Section 2, Specification.
To observe the results after a calibration is completed, press the push button
sequence [Blue-SHIFT] [LIN]. A table appears on the screen that shows
the correction factor used to center the resolution bandwidth filters to produce a calibrated center frequency. It also shows the correction that was
required to bring the amplitude of each filter within 0.4 dB of the 3 MHz filter.
1. To begin the calibration procedure, press the push button sequence
[Blue-SHIFT] [CAL].
2. A prompt message on the screen guides you through setting the four
front-panel adjustments: Vertical and Horizontal POSITION, and AMPL
and LOG CAL. This sets the absolute reference level for the 3 MHz
resolution bandwidth filter.
5-4
Instrument Check Out
Instrument Check Out
3. Next the instrument performs an automatic calibration that measures
and corrects for the absolute frequency and amplitude errors of the
filters (relative to 3 MHz). This takes approximately 60 seconds.
4.
Functional or
Operational Check
If a message appears on the screen, refer to Error Message Readout
earlier in this section. The correction factors are held in memory. Press
either [FINE] to continue calibration as instructed, or [SHIFT] to exit the
routine.
This procedure uses minimum test equipment to check instrument operating
modes, functions, and basic performance. The procedure checks that the
instrument is operating properly. The internal calibrator and attenuator are
used as the source to check most of the operational characteristics. Since
both are very accurate, this check should satisfy most incoming inspection
or pre-operational check-out requirements. This check will also help familiarize you with the instrument operation. A detailed Performance Check that
verifies all performance requirements in Section 2, Specification is included
in the Service Manual, Volume 1.
Equipment Required
The only external equipment used is an N-male-to-BNC-female adapter and
the 50 Q coaxial cable, which are supplied as standard accessories.
Preliminary Preparation
Perform the procedure described under Preparation for Use; then allow the
instrument to warm up for at least 15 minutes before proceeding with this
check.
Check Operation of Front-Panel Push Buttons and Controls
This procedure checks the operation of all front-panel push buttons and
controls, and ensures that the buttons illuminate when the function is active.
The LED lights on the push button when the function is active. Lighted LEDs
also indicate the allowable selections for any of the multiple function push
buttons. For example, all DATA ENTRY push buttons light after [BlueSHIFT] [FREQ], [Blue-SHIFT] [SPAN/DIV], [Blue-SHIFT] [REF LEVEL],
or [Blue-SHIFT] [dB/DIV] shift functions have been selected. Any lighted
push button can enter data for that selection. Messages are displayed on
the screen as guides to the entry sequence of these selections.
495 & 495P User Manual
5-5
Instrument Check Out
Perform these steps before beginning this procedure:
1. Connect the CAL OUT signal to the RF INPUT with the 50 Q cable and
BNC-to-N adapter.
2. Press [Blue-SHIFT] [RESET]; then set the 495/P controls as follows:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . 100MHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20KHZ
VERTICAL SCALE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2DB/
MIN RF ATTEN dB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 (NORM)
TIME/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTO
3. Press or change the following push buttons and controls and note their
effect on the operation.
INTENSITY — Rotate the control through its range and note the CRT beam
brightness change.
HELP — When this mode is activated, press or operate any push button
and most controls to produce a help message on the CRT that explains the
function of that push button or control. Help messages explain any error
message that may appear. Activate this mode, press various push buttons,
and observe the CRT message for each. Press the [HELP] push button
again to cancel. To get HELP messages for shifted functions, press the
desired [SHIFT] push button, press [HELP], then press the desired push
button.
GRAT ILLUM — When activated, the graticule is illuminated.
MARKER MENU — Press this push button to display a menu of available
marker commands that are not permanently assigned to a front-panel push
button.
TRIGGERING —To activate the TRIGGERING mode, press one of four
push buttons. The push button illuminates when in the active state. Press
any one of the push buttons to cancel or deactivate any other mode. Turn
VIEW A and VIEW B off to better observe the triggering effect.
•
FREE RUN — In the active state, the trace free runs.
•
INT — When active, the sweep is triggered when the signal or noise
level at the left edge is > 2.0 division.
1. Use the CENTER/MARKER FREQUENCY control to tune one of the
100 MHz CAL OUT signals to the left edge of the display.
2. Adjust the REFERENCE LEVEL control so that the amplitude of the
signal is 2 or more divisions.
5-6
Instrument Check Out
Instrument Check Out
3.
Press [INT] to activate INT TRIGGERING to trigger the sweep.
4.
Press [FREE RUN].
5. Adjust the REFERENCE LEVEL control so that the amplitude of the
signal is less than 2 divisions.
6. Press [INT] to activate INT TRIGGERING. The sweep is no longer
triggered.
•
LINE — When active, the trace is triggered at power line frequency.
Press [LINE] and the sweep will be triggered.
•
EXT — When this function is active, the trace runs only when an external
signal > 1.0 Vp.p is applied to the rear-panel EXT IN connector. Since
external test equipment is required to check this function, a check
cannot be made with this procedure.
SINGLE SWEEP — When this function is active, single sweep aborts the
current sweep. Press [SINGLE SWEEP] once to enter SINGLE SWEEP
mode. Press [SINGLE SWEEP] again to arm the sweep generator and light
the READY indicator. When triggering conditions are met after the circuit is
armed, the 495/P makes only one sweep. The indicator remains lit until the
sweep has run. The single sweep mode is cancelled when any TRIGGERING push button is pressed. The effect of SINGLE SWEEP mode is more
apparent with VIEW A and VIEW B off.
1. Press [VIEW A] and [VIEW B] to turn these displays off.
2.
Press [FREE RUN] and set the TIME/DIV to 0.5 s.
3.
Press [SINGLE SWEEP] to abort the sweep.
4. Press [SINGLE SWEEP] again. The READY indicator lights and the
sweep runs.
5. Press [FREE RUN] to cancel single sweep.
6.
Return the TIME/DIV to AUTO.
TIME/DIV — This control selects sweep rate, manual scan, and external
sweep operation. In the MNL position, the MANUAL SCAN control moves
the CRT beam across the horizontal axis of the CRT graticule. In the EXT
position, a voltage of 0 to +10 V, applied to the rear-panel HORIZJTRIG
connector, deflects the CRT beam across the full 10-division screen.
VERTICAL DISPLAY — Display modes are activated by three push buttons. Press any of these push buttons to cancel any other mode.
•
495 & 495P User Manual
10 dB/DIV — When this push button is activated, the display is a calibrated 10 dB/division with an 80 dB dynamic range.
1.
Press [VIEW A] and [VIEW B] to turn these displays on.
2.
Set the REFERENCE LEVEL to -20 dBm.
5-7
Instrument Check Out
3. Press [10 dB/DIV].
4.
Set the FREQUENCY SPAN/DIV to 20 kHz.
5. Use the CENTER/MARKER FREQUENCY control to tune the CAL
OUT signal to center screen.
6. Use the REFERENCE LEVEL control to reduce the REFERENCE
LEVEL in 10 dB steps. The display steps in 1 division increments,
representing 10 dB/division.
7.
Return the REFERENCE LEVEL readout to -20 dBm.
• 2 dB/DIV — When this push button is pressed, the display is a calibrated 2 dB/division with 16 dB of dynamic range.
1. Press [2 dB/DIV].
2. Use the REFERENCE LEVEL control to reduce the REFERENCE
LEVEL readout to -6 dBm. The display now steps 1.0 division for
each two steps of the REFERENCE LEVEL control.
3.
•
Return the REFERENCE LEVEL readout to -20 dBm.
LIN — When this push button is pressed, the display is linear between
the reference level (top of the graticule) and zero volts (bottom of the
graticule), and the CRT VERTICAL DISPLAY reads out in volts/division.
1. Press [LIN]. The Vertical Display readout changes to mV/division.
PULSE STRETCHER — When this push button is pressed, the fall-time of
video signals increases so narrow video pulses will show on the display.
1. Select these front-panel control settings:
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
TIME/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 MS
VIEW A and VIEW B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OFF
2. Press [PULSE STRETCHER]. The signal peaks should increase in
brightness.
3. Press [PULSE STRETCHER] to turn off the PULSE STRETCHER mode.
4.
Set the TIME/DIV to AUTO.
5. Press [VIEW A] and [VIEW B] to turn these displays on.
VIDEO FILTER —Two filters can be independently selected to provide
WIDE or NARROW (approximately 1/30th or 1/300lh of the resolution
bandwidth) filtering to reduce noise.
1. Use the CENTER/MARKER FREQUENCY control to tune the 500 MHz
CAL OUT signal to center screen.
2. Change the FREQUENCY SPAN/DIV readout to 2 kHz.
5-8
Instrument Check Out
Instrument Check Out
495 & 495P User Manual
5-9
Instrument Check Out
3. Adjust the REFERENCE LEVEL as needed to view the noise floor.
4. Alternately press the [WIDE] and [NARROW] Video Filter push buttons.
The noise is reduced as the filter is turned on (see Figure 5-3). The
NARROW filter has a more pronounced effect on noise reduction. Note
the change in sweep rate when the TIME/DIV selector is in the AUTO
position.
5. Turn both Video Filters off.
DIGITAL STORAGE — Select either one or both of the A and B
waveforms from digital storage. The amplitude of a signal should remain
constant when digital storage is turned on (VIEW A or VIEW B activated).
The PEAK/AVERAGE control positions a cursor over the vertical window of
the screen. Noise and signal levels are averaged below the cursor and
peak-detected above the cursor.
•
VIEW A — When this push button is pressed, the A waveform from
digital storage is displayed. With SAVE A mode off, the A waveform is
updated each sweep as the beam travels from left to right. With SAVE A
mode on, the waveform is not updated.
•
VIEW B — When this push button is pressed, the B waveform is displayed. When both VIEW A and VIEW B modes are active, the A and B
waveforms are interlaced and displayed. Both waveforms are updated
each sweep. Update of the A waveform depends on the state of SAVE A
mode.
•
SAVE A — When SAVE A mode is activated, the A waveform with its
readout is saved. In this mode, the data for the A waveform is not updated each sweep. If either VIEW B mode or B-SAVE A mode is on, the
readout reflects the current 495/P setup. The readout for the saved
waveform will be displayed any time SAVE A mode is on, and the VIEW
B and B-SAVE A modes are off.
1. Press [SAVE A] to store the waveform in the A register.
2. Press [VIEW B] to turn it off.
3. Change the setting of the REFERENCE LEVEL control. The A
display will not change.
4. Press [SAVE A] to turn this mode off.
•
MAX HOLD — When this push button is pressed, the maximum signal
amplitude at each memory location is stored. The waveform is updated
only when signal data is greater than that previously stored. To verify
operation, perform the following procedure:
1.
Return the REFERENCE LEVEL readout to -20 dBm.
2.
Press [MAX HOLD] to turn this mode on.
3. Change the setting of the CENTER/MARKER FREQUENCY control.
The maximum level at each screen location will be retained.
4. Press [MAX HOLD] to turn this mode off.
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•
B-SAVE A — Press this push button to display the arithmetic difference
between an updated B waveform and a SAVE A waveform. The SAVE A
function is automatically activated when [B-SAVE A] is pressed.
The reference (zero difference) level is factory set at graticule center. The
position of this reference level can be changed by qualified service
personnel. Positive differences between the two displays appear above
this line and negative differences below the line.
1. Press [VIEW A] and [VIEW B] to turn these displays on.
2.
Press [SAVE A] to store the waveform in the A register.
3.
Press [B-SAVE A] to view the difference between the B and SAVE A
waveforms.
4. Press [SAVE A] to turn this mode off.
•
PEAK/AVERAGE — When digital storage is on, this control positions a
horizontal line, or cursor, anywhere within the graticule window. Signals
above the cursor are peak detected. Signals below the cursor are averaged by the digital storage. To verify operation, move the cursor within
the noise level. The noise amplitude will change as the cursor is positioned.
IDENT — When the identify function is turned on, the waveform is vertically
displaced on alternate sweeps. The frequencies of the 1st and 2nd local
oscillators are moved so that true signals are not displaced horizontally on
alternate sweeps while spurious signals are shifted significantly, or off
screen. The FREQUENCY SPAN/DIV setting must be 50 kHz or less before
IDENTIFY mode can be turned on. Refer to Using the Signal Identifier in
Section 6, Operation, for more details.
1. Select these front-panel control settings:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . 1500MHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50KHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40DBM
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
2. Press [IDENT] to turn the IDENTIFY mode on.
3. There will be no horizontal displacement of the 100 MHz signal on
alternate sweeps. To help determine if the signal is true or spurious (see
Figure 5-4), decrease the sweep rate or push [SAVE A] with both VIEW
A and VIEW B on, so a comparison can be made.
4. Press [IDENT] to turn the IDENTIFY mode off.
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AUTO RESOLN — When this push button is pressed and FREQUENCY
SPAN/DIV and TIME/DIV settings are changed, resolution bandwidth is
automatically selected by the processor to maintain a calibrated display. The
UNCAL indicator should not light over the FREQUENCY SPAN/DIV range if
the TIME/DIV selector is in the AUTO position.
1. To check operation, change FREQUENCY SPAN/DIV or TIME/DIV
settings. The RESOLUTION BANDWIDTH will change automatically.
2.
Return the TIME/DIV control to AUTO.
MAX SPAN — When activated, the span switches to maximum and the
495/P sweeps the full band. When deactivated, the FREQUENCY SPAN/DIV
returns to its previous setting.
ZERO SPAN — When activated, the FREQUENCY SPAN/DIV shifts to zero
for a time-domain display. When deactivated, the FREQUENCY SPAN/DIV
returns to its previous setting.
FREQUENCY SPAN/DIV — As this control is rotated, the FREQUENCY
SPAN/DIV changes between 0 and MAX. The display indicates the change.
RESOLUTION BANDWIDTH — As this control is rotated, the resolution
bandwidth changes in decade steps from 10 Hz to 1 MHz, and then to
3 MHz. The AUTO RESOLN mode must be off to change resolution bandwidth with the RESOLUTION BANDWIDTH control.
REFERENCE LEVEL — With 10 dB/DIV VERTICAL DISPLAY active and
FINE mode off, the REFERENCE LEVEL readout steps in 10 dB increments
as the control is rotated. When FINE mode is activated, the steps are 1 dB.
In the 2 dB/DIV mode, the steps are 1 dB with FINE mode off and 0.25 dB
with FINE mode on.
When the Vertical Display factor is 4 dB/div or less with FINE mode on, the
495/P switches to the delta A mode. In the delta A mode, the REFERENCE
LEVEL readout goes to 0.00 dB, then steps in 0.25 dB increments as the
REFERENCE LEVEL control is rotated.
1. Set the MIN RF ATTEN dB control to 0 dB and VERTICAL DISPLAY to
10 dB/DIV.
2. Rotate the REFERENCE LEVEL control counterclockwise to 40 dBm,
then clockwise to -110 dBm. The REFERENCE LEVEL readout
changes in 10 dB increments.
3. Press [FINE].
4. Change the setting of the REFERENCE LEVEL control. The REFERENCE LEVEL readout now steps in 1 dB increments.
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5. Press [Blue-SHIFT] [dB/DIV] and enter 4 dB (press [4] [dB]) with the
DATA ENTRY push buttons. The REFERENCE LEVEL readout goes to
0.00 dB.
6. Rotate the REFERENCE LEVEL control. The REFERENCE LEVEL now
steps in 0.25 dB increments from the 0.00 dB reference.
MIN RF ATTEN dB —This control sets the minimum amount of RF attenuation in the signal path, regardless of the REFERENCE LEVEL control setting.
1. To check operation, select these front-panel control settings:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . 100MH2
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500KHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
F I N E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OFF
2. Set the MIN RF ATTEN dB selector to 20.
3.
Change the REFERENCE LEVEL setting to -50 dBm. The RF ATTENUATION readout will not go below 20 dB.
FINE —When activated, the REFERENCE LEVEL control steps decrease.
Refer to the REFERENCE LEVEL check earlier in this section.
MIN NOISE/MIN DISTORTION — This push button selects one of two
methods that select RF attenuator and IF gain. MIN NOISE mode (button
illuminated) reduces the noise level by reducing attenuation 10 dB and
decreasing IF gain 10 dB. MIN DISTORTION mode reduces IM distortion
due to input mixer overload. To observe any change, the amount of RF
ATTENUATION displayed by the CRT readout must be 10 dB higher than the
MIN RF ATTEN dB selector setting.
1. To check operation, select these front-panel control settings:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500KHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
MIN RF ATTEN dB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 (NORM)
2. The RF ATTENUATION readout will indicate 0 dB.
3. Press [MIN NOISE/MIN DISTORTION] to turn on MIN DISTORTION
mode. The noise floor will rise approximately 10 dB, and the RF ATTENUATION readout will change to 10 dB.
4. Press [MIN NOISE/MIN DISTORTION] to turn on MIN NOISE mode.
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UNCAL — This indicator lights when the display is uncalibrated.
1. Set the TIME/DIV control to 5 ms.
2. Press [AUTO RESOLN] to turn the AUTO RESOLUTION mode off.
3. Set the RESOLUTION BANDWIDTH to 10 kHz.
4. The UNCAL indicator should light and remain lit until the FREQUENCY
SPAN/DIV readout is reduced to 50 kHz, or the RESOLUTION
BANDWIDTH is increased to 100 kHz.
5. Select these front-panel control settings before proceeding:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
AUTO RESOLN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
TIME/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTO
SHIFT — These push buttons shift multiple-function push buttons to their
alternate function. The names of most of these alternate functions are
printed in blue or green lettering next to the push button. The shift mode
deactivates after the function has been performed.
DATA ENTRY push buttons for the shift mode are labeled with orange lettering.
RECALL SETTINGS/STORE — When this push button is pressed, the
495/P lists the settings, with their center frequency, that are stored in
memory (registers 0-9). The 0 register holds the power-down settings so
they can be recalled after power-up. Press [Blue-SHIFT] [STORE] to store
the existing front-panel setup in one of the available registers.
1. Press [Blue-SHIFT] [STORE] and select register number 1 with the
DATA ENTRY push buttons to store the current front-panel setup.
2. Change front-panel push button and control settings.
3. Press [RECALL SETTINGS] [1] to recall the setup.
4. The instrument front-panel set-up returns to that previously entered, with
the exception of the TIME/DIV and RF ATTENUATION settings.
COUNT and [Blue-SHIFT] COUNT RESOLN — Press [COUNT] to
activate a count for any signal within the center two divisions of the screen,
or below the dot marker. The signal to be counted must be 20 dB above the
noise floor and greater than 60 dB below the reference level. The resolution
of the counter is selected when in the Count Resolution mode. Press
[Blue-SHIFT] [COUNT RESOLN] to set counter resolution to 1 Hz using
the DATA ENTRY push buttons and the units terminator push button.
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1. To check the counter operation, select these front-panel control settings:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10KHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +30DBM
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10KHZ
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
F I N E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OFF
2. Adjust CENTER/MARKER FREQUENCY to position the 100 MHz signal
so the 20 dB level, above the noise floor, crosses the center graticule
line.
3. Press [Blue-SHIFT] [COUNT RESOLN] [1] [0] [0] [Hz] to establish a
counter resolution of 100 Hz.
4. Press [COUNT] to display the counted frequency to 100 Hz resolution.
5. Press [COUNT] again to turn off the COUNT mode.
A F — When the delta F function is activated, FREQUENCY readout initializes to 0. The frequency difference, to a desired signal or point on the display, can be determined by tuning that point to center screen and noting the
readout. If the delta frequency is tuned below 0, the readout will include a
minus sign.
1. To check the operation, select these front-panel control settings:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . 500MHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50MHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTO
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
2.
Press [AF]. The FREQUENCY readout resets to 0 MHz.
3. Rotate the CENTER/MARKER FREQUENCY clockwise to position the
next signal peak at center screen. The FREQUENCY readout should not
read 100 MHz.
4. Press [AF] to turn off the AF mode.
TUNE CF/MARKER — When this push button is lit, a marker appears as a
bright spot on the screen and the CENTER/MARKER FREQUENCY control
tunes the marker. The FREQUENCY readout remains constant. An asterisk
(*) between the FREQUENCY and REFERENCE LEVEL readout indicates
that the CENTER/MARKER FREQUENCY control is tuning the Marker Frequency. The marker level and marker frequency appear on the second
readout line on the screen.
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+STEP/-STEP — When one of these push buttons is pressed, the MARKER or CENTER FREQUENCY is increased or decreased by increments. The
increment is set with the [Blue-SHIFT] [STEP ENTRY] (CENTER FREQUENCY) or [Green-SHIFT] [STEP SIZE] (MARKER) push button sequence. Perform the following steps while in the TUNE CF mode (LED not
lit):
1. Select these front-panel control settings:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . . OOMHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50MHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTO
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
2. Press [Blue-SHIFT] [STEP ENTRY], and enter 25 MHz with the DATA
ENTRY push buttons (press [2] [5] [MHz]).
3. Press [+STEP]; the FREQUENCY readout increases to 125 MHz.
4. Press [+STEP] again and the FREQUENCY readout increases to
150 MHz.
5. Push [-STEP] twice and the FREQUENCY readout decreases to
125 MHz and 100 MHz, respectively.
[Blue-SHIFT] MACRO MENU — (495P Instruments Only) This push
button is used to select a macro to be run. The title of the macro is displayed next to the macro number (0-7) . Perform the following steps to
check out the operation of the [MACRO MENU] push button.
With the instrument under remote control, enter the following 4041 test
program to enter a macro into menu location 5:
80 Z=1 ! ADDRESS OF SPECTRUM ANALYZER
100 Print #z:KILL 5
110 Print #z:STMAC 5,"return test"
120 Print #z:FREQ 100M; GOSUB 1; FREQ 200M; GOSUB 1;
FREQ 300M; GOSUB 1; DONE
130 Print #z:LABEL 1; SWEEP; MFGIB; MCSTOP; RETURN
140 Print #z:EMAC
Line 80 defines z as the spectrum analyzer address. Line 100 clears out
location 5 in case there was already a macro there. Line 110 gets the spectrum analyzer ready to store macro in location 5 with the title of "return test."
Line 120 sets the CENTER FREQUENCY to 100 MHz and prepares the
spectrum analyzer to check the CENTER FREQUENCY again at 200 MHz
and 300 MHz. Line 130 starts a new sweep and waits until the sweep has
finished before executing the next command; moves the primary marker to
the peak of the largest on-screen signal; stops the macro to wait for you to
press [RUN/STOP] on the instrument front panel to continue; and returns to
line 120 to find the next CENTER FREQUENCY setting (200 MHz). This
sequence is followed for the 200 MHz and 300 MHz settings. Line 140 tells
the spectrum analyzer that this is the end of the macro and to quit storing.
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1. Press [RESET TO LOCAL] to exit remote control and return the instrument to local control.
2. Press [Blue-SHIFT] [MACRO MENU]. The current macro menu will
appear on the screen with the titles of all stored macros and the menu
locations where they are stored.
3. To select the test program just entered into location 5, press DATA
ENTRY push button 5. The macro will begin running.
4. When the macro has moved the primary marker to the peak of the
100 MHz signal, the macro will wait (MCSTOP) for you to push [RUN/
STOP] to run another sweep at 200 MHz.
5. When the macro has moved the primary marker to the peak of the
200 MHz signal, the macro will wait (MCSTOP) for you to push [RUN/
STOP] to run another sweep at 300 MHz.
6. If you press [RESET TO LOCAL] at any time, the message
MACRO=STOP(5) will appear on the right-center of the screen. This
means that the macro in menu location 5 is now running. This will not
interrupt the macro.
7. When the macro has moved the primary marker to the peak of the
300 MHz signal, the macro will know that it is done.
8.
If you press [RESET TO LOCAL] now, the message MACRO=OFF(5)
will appear on the screen. This means that the last macro you were
running was from menu location 5 and it is now off.
[Blue-SHIFT] RUN/STOP — (495P Instruments Only) This push button
has three different functions, depending on the current status of the macros.
1. If a macro is running, pressing [RUN/STOP] will stop the macro.
2. If a macro is stopped (because [RUN/STOP] was pressed or because
of the MCSTOP command as in the MACRO MENU example), pressing
[RUN/STOP] restarts the macro.
3. If there is no macro running or stopped, pressing [RUN/STOP] will
cause the last macro that was run to be run again.
RESET TO LOCAL — (495P Instruments Only) The [RESET TO LOCAL]
push button is lighted when the 495P is under control of a GPIB controller.
While under remote control, the other front-panel controls are not active, but
indicators will still reflect the current state of all front-panel functions, except
TIME/DIV, PEAK/AVERAGE and MIN RF ATTEN dB.
This push button is not lighted when the 495P is under local operator control. While under local control, the 495P does not execute GPIB messages
that would conflict with front-panel controls or change the waveforms in
digital storage.
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When the push button is pressed, local control is restored to the operator
unless the controller prevents this with the local lockout message. Programmable functions do not change when switching from remote to local control,
except as necessary to match the settings of front-panel controls for TIME/
DIV, MIN RF ATTEN dB, and PEAK/AVERAGE.
The internal instrument and front-panel firmware version numbers and the
GPIB address are flashed on the CRT when the push button is pressed. The
GPIB primary address is updated if the GPIB ADDRESS switches have been
changed.
For another function of this push button when in the talk-only mode, refer to
Talk-Only/Listen-Only Operation in Section 6 of this manual.
GPIB Function Readout — (495P Instruments Only) A single character
appears in the lower CRT readout when the 495P is talking (T), listening (L),
or requesting service (S). Two characters will appear in this location if the
495P is talking or listening and also requesting service, or is in the talk/listen
mode.
DATA ENTRY — Some functions require a parameter or command to be
entered that includes numerical data. This data is entered with the DATA
ENTRY push buttons as follows:
1. Select these front-panel control settings:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . 500MHZ
FREQUENCY SPAN/DIV ................................ 50KHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTO
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
2. Press the push button sequence [Blue-SHIFT] [FREQ] [5] [Q] [0]
[MHz] using the DATA ENTRY push buttons. This sets the FREQUENCY
to 500.000 MHz. (The displayed readout resolution is a function of the
current FREQUENCY SPAN/DIV setting.)
3. With the DATA ENTRY push buttons, set the SPAN/DIV readout to any
desired setting (press [Blue-SHIFT] [SPAN/DIV] [5] [2] [MHz] for a
52 MHz/DIV setting as an example). The FREQUENCY SPAN/DIV
readout will be set to the figures entered with the DATA ENTRY push
buttons (rounded to 2 digits).
4. Enter a reference level with the DATA ENTRY push buttons (press
[Blue-SHIFT] [REF LEVEL] [3] [2] [-dBx] fora -32 dBm setting as
an example). The REFERENCE LEVEL readout will be set to the figures
entered with the DATA ENTRY push buttons.
5. Enter a desired VERTICAL DISPLAY factor with the DATA ENTRY push
buttons (press [Blue-SHIFT] [dB/DIV] [5] [dB] for a 5dB/DIV setting
as an example). The VERTICAL DISPLAY readout will be set to the
figures entered with the DATA ENTRY push buttons (rounded to 2 digits).
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STORE DISP — Press [Blue-SHIFT] [STORE DISP], the register number
where you want to store the display, and the display (A or B) you want
stored (only if SAVE A mode is on).
RECALL — Press [Blue-SHIFT] [RECALL], the register number from the
displayed menu, and the part of digital storage (A or B) where you want to
have the recalled waveform placed.
SAVE A mode is automatically activated to prevent an overwrite. If A is
selected, VIEW A must be on to observe the recalled waveform and VIEW B
must be off to see the readout that applies to the recalled waveform. If VIEW
B and VIEW A are on, both the recalled waveform in A and the current
waveform in B will be displayed. Readout will apply to the current B
waveform.
If B is selected, the next sweep will overwrite the display unless SINGLE
SWEEP mode was activated before selecting B. A message will appear on
the screen as a reminder of this. VIEW B must be on to observe the recalled
waveform and its readout. Remember to deactivate SINGLE SWEEP mode
when leaving this recalled mode.
1. Establish a display on the screen.
2.
Press [Blue-SHIFT] [STORE DISP] followed by the memory register
number (0-8) to place the display in a memory register, and the display
(A or B) you wish stored (only if SAVE A mode is on).
3. Change the characteristics of the current display with either the REFERENCE LEVEL or FREQUENCY SPAN/DIV control.
4.
Press [Blue-SHIFT] [RECALL] followed by the register number where
the display was stored (note the center frequency listing of the stored
displays in each register); then press [VIEW A] so the recalled waveform
is placed in the A storage register.
5. If VIEW A is on and VIEW B off, the recalled display with its readout will
now become the A display. SAVE A mode will activate to prevent overwrite. If VIEW A and VIEW B are on, both the recalled display and the
current B display will be on screen. Since the most current display is the
B waveform, the readout will show the parameters for the B display.
Switch VIEW B off to see the readout applicable to the recalled A
waveform.
6. Recall a stored display into the B section by repeating the process just
described. Before starting the process, press [SINGLE SWEEP] so the
recalled waveform will not be overwritten by the next sweep. A message
will appear when you select the B section to remind you of this. When
returning to normal operation, remember to turn off SINGLE SWEEP
mode if you have not already done so.
NOTE
If an attempt is made to recall a display from an empty location,
error message NON-VOLATILE RAM will be displayed.
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MKR OFF — Press [Blue-SHIFT] [MKR OFF] to turn off the markers.
MKR -» CENTER — Press [Blue-SHIFT] [MKR -> CENTER] to bring a
marker signal to center screen.
1. Select these front-panel control settings:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200KHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100KHZ
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
2. Use the CENTER/MARKER FREQUENCY control to tune the signal two
divisions from center-screen.
3. Press [TUNE MKR] to turn on a marker.
4. Use the CENTER/MARKER FREQUENCY control to tune the Marker to
the top of the signal.
5.
Press [Blue-SHIFT] [MKR
move to center screen.
CENTER]. The signal and Marker should
READOUT — Press [Blue-SHIFT] [READOUT] to turn off the CRT
readout of the REFERENCE LEVEL, FREQUENCY, SPAN/DIV, VERTICAL
DISPLAY, RF ATTENUATION, FREQ RANGE, RESOLUTION BANDWIDTH,
VIDEO FILTERS, MKR LEVEL, and MARKER FREQUENCY.
Press [Blue-SHIFT] [READOUT] to activate the readout on the display.
FREQ START STOP — Activating [Blue-SHIFT] [FREQ START STOP]
allows you to enter a start and stop frequency with the DATA ENTRY push
buttons. Use the following example:
1. Enter a start frequency of 90 MHz with the DATA ENTRY push buttons
(press [Blue-SHIFT] [FREQ START STOP] [9] [0] [MHz]).
2. Enter stop frequency 210 MHz with the DATA ENTRY push buttons
(press[2][1][0][MHz]).
3. The signals at the 1st and 9th graticule line should be 100 MHz apart. Set
the VERTICAL DISPLAY to 10 dB/DIV and observe that the FREQUENCY SPAN/DIV readout is 12 MHz.
STEP ENTRY —Activate [Blue-SHIFT] [STEP ENTRY] to set the step to
a desired amount. Perform the following steps while in the TUNE MARKER
mode (TUNE CF/MKR LED lit).
1. Press [Blue-SHIFT] [STEP ENTRY] and enter a step frequency of
10 MHz with the DATA ENTRY push buttons (press [Blue-SHIFT]
[FREQ START STOP] [1] [0] [MHz]).
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2. Press [+STEP] and note that the MARKER FREQUENCY readout increases by 10 MHz (160 MHz).
3. Press [-STEP] to return the MARKER FREQUENCY setting to 150 MHz.
4. Press [TUNE MKR] to turn the marker off.
BASELINE CLIP — Press [Blue-SHIFT] [BASELINE CLIP] to clip
(blank) the baseline of the display up to about one graticule division.
RESET — Press [Blue-SHIFT] [RESET] to return the instrument to the
original power-up state.
REFERENCE LEVEL UNITS — Use this feature to change the REFERENCE LEVEL readout units, or to apply an offset value.
1. Change the REFERENCE LEVEL readout to 0 dBm.
2.
Press [Blue-SHIFT] [REFERENCE LEVEL UNITS].
3. Select item 1 (DBV). The REFERENCE LEVEL readout changes to
-13dBV.
4.
Press [Blue-SHIFT] [REFERENCE LEVEL UNITS] [0] to return to dBm
units.
Green-SHIFT Functions — Press [Green-SHIFT] to change the push
buttons that have more than one function. Some functions require a parameter or command to be entered that includes numerical data. This data is
entered with the DATA ENTRY push buttons. Most green-shifted functions
are marker related.
Markers — The markers provide direct readout of frequency and amplitude
information of any point along any displayed trace or relative (delta frequency), and amplitude information between any two points along any displayed
trace or traces (in delta only). In the delta mode, only the difference in frequency and amplitude will be displayed. Two independent marker frequencies and amplitudes cannot be displayed at the same time.
1. Select these front-panel control settings:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5MHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -10DBM
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTO
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
2. Press [TUNE CF/MKR]. A bright dot, the marker, appears on screen, as
well as a second line of readout with an asterisk between the MKR
LEVEL and MARKER FREQUENCY readout.
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3. Rotate the CENTER/MARKER FREQUENCY knob, and note that the
marker tunes.
4. Press [TUNE CF/MKR] again. The indicator button will not be lit, but the
marker remains on screen.
5.
Rotate the CENTER/MARKER FREQUENCY control and note that the
signal tunes. The marker does not move, but both the CENTER FREQUENCY and the MAR0ER FREQUENCY readouts change. Also, the
asterisk has now moved to the first readout line, indicating that the
center frequency is being tuned.
6. Return the FREQUENCY readout to 100 MHz and press [TUNE CF/
MKR] to activate the marker.
PEAK FIND — Press [Green-SHIFT] [PEAK FIND] to move the marker to
the top of the signal.
D MKR, 1<-MKR->2, MKR START STOP, MKR -> REFERENCE LEVEL,
ASSIGN 1, ASSIGN 2 — Press [Green-SHIFT] [A MKR] to activate a
second marker at the position of the single marker on the trace. Parentheses
will be added to the second line readout.
1. Rotate the CENTER/MARKER FREQUENCY control. Two markers will
be on screen. Set the delta marker readout to 5 MHz.
2. Press [Green-SHIFT] [1<-MKR->2]. The left marker is now brighter.
This indicates that it will be tuned.
3.
Rotate the CENTER/MARKER FREQUENCY control to tune the marker
until the readout shows -10 MHz. This is the difference in frequency
between the two markers (the delta marker frequency).
4. Press [Green-SHIFT] [MKR START STOP]. The markers now appear
at the left and right edge of the screen. The waveform will be scaled to
the marker locations.
5. Press [Green-SHIFT] [A MKR] again. There will be just a single marker now, and the parentheses around the second line of readout will
disappear.
6. Press [Green-SHIFT] [PEAK FIND]; then [Blue-SHIFT]
[MKR-»CENTER]. The signal is now at center screen.
7.
Press [Green-SHIFT] [MKR->REFERENCE LEVEL]. The signal and
the marker move to the top of the screen.
8. Set the FREQUENCY SPAN/DIV readout to 500 kHz.
9. Set the RESOLUTION BANDWIDTH to 1 MHz (press [AUTO RESOLN]
first).
10. Press [MARKER MENU]. Nine menu items are displayed.
11. Press [7] and you will be prompted to enter the bandwidth number.
12. Enter 10 dB with the DATA ENTRY push buttons (press [1] [0] [dB]).
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13. Press [Green-SHIFT] [BANDWIDTH MODE] and observe that the
Delta Markers have moved down 10 dB from the top of the signal. Delta
frequency is slightly greater than 1 MHz wide.
14. Press [Green-SHIFT] [BANDWIDTH MODE] again to exit BANDWIDTH MODE.
15. Press [Blue-SHIFT] [MKROFF].
16. Use the DATA ENTRY push buttons to set the FREQUENCY readout to
200 MHz and the FREQUENCY SPAN/DIV readout to 25 MHz.
17. Set the Peak/Average cursor to the bottom of the screen.
18. Press [TUNE CF/MKR].
19. Press [Green-SHIFT] [PEAK FIND]. The marker will now be located
on the 100 MHz CAL OUT (the signal nearest the left edge of the
screen).
20. Press [MARKER MENU]. Nine menu items are displayed.
21. Press [6] and the ASSIGN MENU is displayed with seven menu items.
22. Press [3] and note that both [ASSIGN] push buttons light.
23. Press [Green-SHIFT] [ASSIGN 1] to assign the Next Lower Peak
function.
24. Press [MARKER MENU] again.
25. Press [6] to get the ASSIGN MENU.
26. Press [2].
27. Press [Green-SHIFT] [ASSIGN 2] to assign the Next Higher Peak
function.
28. Press [Green-SHIFT] [ASSIGN 2]. The marker will move to the
300 MHz CAL OUT harmonic.
29. Press [Green-SHIFT] [ASSIGN 2] one more time. The marker will
move to the 200 MHz CAL OUT harmonic.
30. Press [Green-SHIFT] [ASSIGN 1] twice to return the marker to the
original 100 MHz signal.
31. Press [TUNE CF/MKR] to turn the marker off.
SIGNAL TRACK — Press the [Green-SHIFT] [SIGNAL TRACK] sequence to keep a drifting signal on screen.
1. Select these front-panel control settings:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5KHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1KHZ
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VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
2. Use the CENTER/MARKER FREQUENCY control to tune the signal
away from center-screen. The signal should be on screen.
3. Press [Green-SHIFT] [SIGNAL TRACK]. The signal will move back to
center screen. SIGNAL TRACK will be indicated in the marker readout
on the screen.
4. To exit the function, press [Green-SHIFT] [SIGNAL TRACK] again.
Gain Variation Between Resolution Bandwidths
Less than < ±0.4 dB with respect to the 3 MHz filter, <0.8 dB between any
two filters.
1. Press [Blue-SHIFT] [CAL] and perform the steps prompted by the
495/R
2. Apply the CAL OUT signal to the RF INPUT, press [Blue-SHIFT]
[RESET], and set the 495/P controls as follows:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1MHZ
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3MHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -18DBM
MIN RF ATTEN dB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 (NORM)
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1DB/
WIDE VIDEO FILTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
TIME/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTO
PEAK/AVERAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fully Clockwise
3. Adjust the AMPL CAL control to align the signal peak at the 6th graticule
line and press [SAVE A].
4. Change the RESOLUTION BANDWIDTH to 1 MHz and SPAN/DIV to
200 kHz. Check that amplitude deviation from the 3MHZ reference
(SAVE A trace) is no more than ±0.4 dB.
5. Change the RESOLUTION BANDWIDTH to 100 kHz (300 kHz for
Option 07) and the SPAN/DIV to 50 kHz.
6. Set the RESOLUTION BANDWIDTH to each of the remaining settings
(10 kHz to 10 Hz). Check that amplitude deviation from the 3 MHz
reference level is no more than ±0.4 dB.
Frequency Span/Div Accuracy
Frequency Span/Div Accuracy is ±5% of the selected Span/Div over the
center 8 divisions of a 10 division display for values >50 Hz/Div, and ±10%
of the selected span/div over the center 8 divisions of a 10 division display
for values <50 Hz/Div.)
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Span accuracy is the displacement error of CAL OUT markers from the
center reference over the center 8 divisions of span. Linearity accuracy is
determined by the displacement of CAL OUT signal markers from their
specified positions over the center eight divisions of the display area, using
the 1st graticule line as the reference.
1. Press [Blue-SHIFT] [RESET]; then set the 495/P controls as follows:
CENTER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1GHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTO
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -30DBM
TIME/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTO
VERTICAL DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 DB/
2. Apply the CAL OUT signal to the RF INPUT.
3. Set the CENTER/MARKER FREQUENCY control to align the 100 MHz
markers so that the 100 MHz/Div accuracy can be measured over the
center eight divisions of the display. It may be necessary to change the
REFERENCE LEVEL to obtain adequate marker amplitude.
4. Span is accurate when the 100 MHz lines are within 5% (2 minor divisions) of their reference graticule line over the center eight divisions. (It
may be easier to observe the lines with DIGITAL STORAGE off.)
5. Linearity is accurate when the displacement of successive lines, over the
center eight divisions, does not exceed 5% of 100 MHz (the FREQUENCY SPAN/DIV setting) or 0.2 division.
Resolution Bandwidth and Shape Factor
6 dB bandwidth within 20% of the selected bandwidth for all but the 10 Hz
filter.
Shape factor is 7.5:1 or less for all bandwidths except the 10 Hz bandwidth.
The 10 Hz filter has a 60 dB bandwidth < 150 Hz.
1. Apply the CAL OUT signal to the RF INPUT; then press [Blue-SHIFT]
[RESET] and set the 495/P controls as follows:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . 100MHZ
SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1MHZ
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3MHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
VERTICAL D I S P L A Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2DB/
PEAK/AVERAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fully Clockwise
TIME/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTO
2. Press [Green-SHIFT] [BANDWIDTH] to turn on Bandwidth mode.
3.
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Press [MARKER MENU] [7] [6] [dB] to select a 6 dB bandwidth.
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Table 5-1: Resolution Bandwidth and Shape Factor
Filter
6 dB Bandwidth
60 dB Bandwidth
Shape Factor
3 MHz
1 MHz
300 kHz
100kHz
10kHz
1 kHz
100 Hz
4. Record the measured 6 dB bandwidth for the 3 MHz filter in Table 5-1
(see Figure 5-5A). Bandwidth should equal 3 MHz ±600 kHz.
5.
Reduce the RESOLUTION BANDWIDTH to 1 MHz and the SPAN/DIV
to 200 kHz.
NOTE
Press [Green-SHIFT] [PEAK FIND] if the markers do not return to
the signal after changing Resolution Bandwidth settings,
6. Record the 6 dB bandwidth of the 1 MHz filter.
7.
Reduce the RESOLUTION BANDWIDTH to 100 kHz and the SPAN/DIV
to 20 kHz (300 kHz and 50 kHz for Option 07).
8.
Record the 6 dB bandwidth of the 100 kHz (300 kHz) filter.
9.
Reduce the RESOLUTION BANDWIDTH to 10 kHz and the SPAN/DIV
to 5 kHz.
10. Record the 6 dB bandwidth of the 10 kHz filter.
11. Reduce the RESOLUTION BANDWIDTH to 1 kHz and the SPAN/DIV to
200 Hz.
12. Record the 6 dB bandwidth of the 1 kHz filter.
13. Reduce the RESOLUTION BANDWIDTH to 100 Hz and the SPAN/DIV
to 20 Hz.
14. Record the 6 dB bandwidth of the 100 Hz filter.
15. Press [MARKER MENU] [7] to select a new Bandwidth value, and enter
[6] [0] [dB].
16. Press [10dB/DIV].
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17. Reduce the RESOLUTION BANDWIDTH to 10 Hz. The 60 dB band-
width should not exceed 150 Hz.
18. Increase the RESOLUTION BANDWIDTH to 100 Hz and the SPAN/DIV
to 200 Hz.
19. Record the 60 dB bandwidth of the 100 Hz filter.
20. Increase the RESOLUTION BANDWIDTH to 1 kHz and the SPAN/DIV
to 2 kHz.
21. Record the 60 dB bandwidth of the 1 kHz filter.
22. Increase the RESOLUTION BANDWIDTH to 10 kHz and the SPAN/DIV
to 10 kHz.
23. Record the 60 dB bandwidth of the 10 kHz filter.
24. Increase the RESOLUTION BANDWIDTH to 100 (300) kHz and the
SPAN/DIV to 500 kHz.
25. Record the 60 dB bandwidth of the 100 (300) kHz filter.
26. Increase the RESOLUTION BANDWIDTH to 1 MHz and the SPAN/DIV
to 1 MHz.
27. Record the 60 dB bandwidth of the 1 MHz filter.
28. Increase the RESOLUTION BANDWIDTH to 3 MHz and the SPAN/DIV
to 2 MHz.
29. Record the 60 dB bandwidth of the 3 MHz filter.
30. Using the 6 dB and 60 dB values recorded in Table 5-1, calculate the
shape factor of all filters >10 Hz. Check that the shape factor is 7.5:1 or
less. The shape factor is the ratio of —60 dB/—6 dB bandwidths (see
Figure 5-5).
Check Reference Level Gain and RF Attenuator Steps
1. Apply the CAL OUT signal to the RF INPUT; then press [Blue-SHIFT]
[RESET] and set the 495/P controls as follows:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . 100MHZ
FREQUENCY SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100KHZ
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . 100KHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
VERTICAL D I S P L A Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10DB/
NARROW VIDEO FILTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
TIME/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTO
1. To check the RF Attenuator, increase REFERENCE LEVEL readout to
+40 dBm. The signal peak will decrease 1 major division per 10 dB step
of the RF ATTENUATION readout.
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Table 5-2: 50 O Sensitivity Equivalent Input Noise Versus Resolution Bandwidth3
Frequency
Range
"IMHztO
10 Hz
100 Hz
1kHz
10kHz
100kHz
300 kHzb
1 MHz
3 MHz
-131 dBm
-125dBm
-115dBm
-105dBm
-95dBm
-90dBm
-85dBm°
-80dBmd
1.8 GHz
a
Equivalent maximum input noise (average noise for each resolution bandwidth).
b
Option 07 replaces the 100 kHz filter with a 300 kHz filter.
c
Above 5 MHz.
"Above 10 MHz.
2. Set the 495/P controls as follows:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . 200MHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
3. Increase the MIN RF ATTEN dB to 60 dB. The noise level will increase
1 division for each 10 dB step. Keep the MIN RF ATTEN dB set to
60 dB.
4. To check IF gain steps, switch the REFERENCE LEVEL control between
-20 dBm and +40 dBm. The noise level will decrease 1 division per
step.
5. Press [FINE]; then check that the trace rises 1 dB/step as the REFERENCE LEVEL is changed from +40 dBm to +30 dBm.
6. Press [FINE] again to turn the FINE mode off.
7. Set the MIN RF ATTEN dB setting to 0 dB.
8. Press [MIN NOISE/MIN DISTORTION] to select the MIN DISTORTION
mode. The noise floor will rise about 1 division and the RF ATTENUATION increases 10 dB. The REFERENCE LEVEL readout should not
change.
9. Set the 495/P controls as follows:
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -60DBM
VERTICAL D I S P L A Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2DB/
10. Adjust REFERENCE LEVEL so the signal level is near the top graticule
line.
11. Change the REFERENCE LEVEL to -54 dBm. The REFERENCE LEVEL readout will change in 1 dB steps, and the display in 1 division steps.
12. Set VERTICAL DISPLAY readout to 1 dB/DIV (press [Blue-SHIFT]
[dB/DIV] [1] [dB]).
13. Change the REFERENCE LEVEL to -60 dBm. The signal amplitude will
change in 1 dB increments (0.5 div).
14. Press [FINE] (Delta A mode). The REFERENCE LEVEL now reads
0.00 dB which denotes the Delta A mode.
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15. Change the REFERENCE LEVEL control position. The REFERENCE
LEVEL readout will change in 0.25 dB increments.
16. Press [FINE] again to turn the FINE mode off.
Sensitivity, 1 MHz to 1.8 GHz
Refer to Table 5-2 for specifications. See Section 2, Specification for specifications relating to the 100 Hz to 1 MHz frequency range.
NOTE
Sensitivity is specified according to the input mixer average noise
level. The calibrator signal is the reference used to calibrate the
display.
1. Remove the CAL OUT signal from the RF INPUT, and terminate the
Type N RF INPUT in its characteristic impedance of 50 Q.
2. Press [Blue-SHIFT] [RESET]; then set the 495/P controls as follows:
SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MAX
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3MHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -85DBM
VERTICAL SCALE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2DB/
MIN RF ATTEN dB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 (NORM)
WIDE VIDEO FILTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
TIME/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 S
PEAK/AVERAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fully Clockwise
3. Press [TUNE]. Use the CENTER/MARKER FREQUENCY control to
place the marker on the highest noise floor location. This is usually near
the right edge of the screen.
4.
Press [ZERO SPAN].
5.
Check that the marker amplitude readout indicates -80 dBm or less.
6.
Press [AUTO RESOLN] to turn off AUTO RESOLUTION mode, and
select the 1 MHz filter.
7. Set the REFERENCE LEVEL so that the trace is near mid-screen.
8.
Check that the marker amplitude readout indicates —85 dBm or less.
9.
Select the 100 kHz (300 kHz) filter.
10. Set the REFERENCE LEVEL so that the trace is near mid-screen.
11. Check that the marker amplitude readout indicates -95 dBm
(-90 dBm) or less.
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12. Check that the noise level of the remaining filters (10 kHz to 10 Hz) is
less than or equal to the value shown in Table 5-2. To measure the noise
level of each filter, set the REFERENCE LEVEL so the trace is near
mid-screen.
NOTE
Use a VERTICAL SCALE factor of 4 dB/div. to measure the 10 Hz
filter noise level.
Residual FM
Residual FM is within 7 kHz over 20 ms with SPAN/DIV greater than 200 kHz,
and 5 Hz over 20 ms with FREQ SPAN/DIV of 200 kHz or less.
1. Apply the CAL OUT signal to the RF INPUT.
2. Press [Blue-SHIFT] [RESET]; then set the 495/P controls as follows:
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -23DBM
CENTER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1MHZ
VERT DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 DB/
3. Disable the 1st LO synthesis and phase lock by pressing [Blue-SHIFT]
[10 dB/DIV]. The message FREQUENCY CORRECTIONS DISABLED:
PRESS "HELP" will appear on the screen.
4. Set the SPAN/DIV to 100 kHz. Use the FREQUENCY/MARKER control
to center the 100 MHz CAL OUT signal on screen.
5.
Press [AUTO RESOLN] and change the RESOLUTION BANDWIDTH to
100kHz.
6. Press [LIN]. Use the FREQUENCY/MARKER control to position the
signal so the slope (horizontal versus vertical excursion) of the response
can be determined as shown in Figure 5-6A. The slope is usually about
10 kHz/division.
7. Press [ZERO SPAN], then set TIME/DIV to 20 ms.
8. Adjust the FREQUENCY/MARKER control to position the trace near
center screen as shown in Figure 5-6B. Press [SAVE A] to freeze the
display for ease in measuring FM. The peak-to-peak amplitude of the
display (number of vertical divisions) within any given horizontal division,
scaled to the vertical deflections according to the slope estimated in
part e, is the FM. Residual FM must not exceed 7 kHz for 20 ms or
7 kHz/division.
9. Press [Blue-SHIFT] [10 dB/DIV] to enable the phase lock. If SAVE A
mode was used in part 8, press [SAVE A].
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10. Press [Blue-SHIFT] [FREQ] [1] [0] [0] [MHz], then press [ZERO
SPAN].
11. Return the TIME/DIV to AUTO.
12. Reduce the FREQ SPAN/DIV to 10 Hz and RESOLUTION BANDWIDTH
to 10 Hz.
13. Use the FREQUENCY/MARKER control to move the trace to a graticule
line so its slope can be determined. See Figure 5-6A.
14. Switch the TIME/DIV to 20 ms and press [ZERO SPAN].
15. Adjust the FREQUENCY/MARKER control to position the trace near
center screen as shown in Figure 5-6B. Press [SAVE A] to freeze the
display for ease in measuring FM. The peak-to-peak amplitude of the
display (number of vertical divisions) within any given horizontal division,
scaled to the vertical deflections according to the slope estimated in part
13, is the FM. Residual FM must not exceed 5 Hz for 20 ms or 5 Hz/division.
Center Frequency Stability
Drift is 50 Hz/min or less with the 1st LO locked (SPAN/DIV<200 kHz) after
1 hour of warmup time in a stable ambient temperature.
1. Apply the CAL OUT signal to the RF INPUT.
2. Press [Blue-SHIFT] [RESET]; then set the 495/P controls as follows:
CENTER/MARKER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . 100MHZ
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -20DBM
SPAN/DIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50HZ
RESOLUTION BANDWIDTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100HZ
VERT DISPLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2DB/
3. Press [Blue-SHIFT] [PULSE STRETCHER] [6]. A message FREQUENCY CORRECTIONS DISABLED: "PRESS HELP" will appear on the
screen. This disables the Frequency Corrections while maintaining the
signal on the screen.
4.
Press [SAVE A] to save the display.
5. Wait 60 seconds.
6. Note the frequency difference between the active and saved displays.
Check that the frequency drift is no more than 50 Hz (1 major division).
5-34
Instrument Check Out
This section describes the normal operating features of the 495/P Spectrum
Analyzer. Many instrument features and operating modes are described,
and examples are included to show some typical applications.
Instrument Operating
Features
Firmware Version and Error Message Readout
Refer to Section 5, Instrument Check Out for information.
CRT Light Filters
Two light filters, amber and grey, are supplied as standard accessories to
the instrument. Select the filter that best suits the surrounding light conditions, light reflections, and your viewing needs. To install the filter, pull the
top of the plastic mask out and place the filter behind it. Remove the light
filter when taking display photographs.
Intensity Level and Beam Alignment
Operate the instrument with the intensity level no higher than that required
to clearly see the display. Trace alignment and beam focus are internal
adjustments that must be performed by qualified service personnel. When
the markers are turned on, set the intensity below the level where dot
"blooming" or defocusing occurs.
The required intensity level for some displays may be high enough to produce a bright and flared baseline. This bright baseline can be eliminated
(clipped) with the [Blue-SHIFT] [BASELINE CLIP] push button sequence.
BASELINE CLIP mode is useful when photographing displays, and it also
allows the lower readout characters to be more easily viewed.
Signal Application
Signal frequencies to 1.8 GHz can be applied through a short, high-quality,
50 Q coaxial cable to the RF INPUT connector. These signals pass through
an internal RF attenuator before application to the 1st mixer.
RF INPUT Connector
The nominal input impedance of the coaxial RF INPUT is 50 Q, and 75 Q on
the optional 75 Q INPUT (Option 07). Because cable losses can be significant at microwave frequencies, it is important to keep the cables as short as
possible. Impedance mismatch between the signal source and the RF
495 & 495P User Manual
6-7
Operation
INPUT will produce reflections that degrade flatness, frequency response,
and sensitivity, and may increase spurious responses. Impedance mismatch
can be caused by poor connections, incorrect signal source impedance,
and long or low-quality coaxial cable. When optimum flatness or frequency
response is desired and signal strength is adequate, set the MIN RF ATTEN dB control to 10 dB or more. The addition of the attenuator helps
minimize reflections to improve the input characteristics.
The front end of the spectrum analyzer is specified at +30 dBm
maximum. It is possible to set the reference level to +40 dBm with
MIN NOISE activated. If the signal level is increased for a fullscreen display, the input level will exceed the power rating of the
attenuator. Do not apply any DC potential to the RF INPUT. Use a
DC block if a signal is riding on any DC potential. For DC block
ordering information, see the Optional Accessories in the 495/495P
Sen/ice Manual, Volume 2, or contact your local Tektronix Field
Office or representative.
Spurious responses can be minimized if the signal amplitude is kept within
the graticule window. A recommended procedure is to select a reference
level setting that limits stronger signals to the graticule window.
High-level signals can cause compression. If excessive signals are applied
(above +30 dBm or +20 dBm when MIN NOISE mode is on), the 1st mixer
attenuator may be destroyed. Signals above +30 dBm must be reduced by
external attenuators. Ensure that the frequency range of any external attenuator is adequate.
Line impedance stabilizing networks, used for conducting EMI/RF measurements, will often have several volts of 60 Hz signal at the output. To protect
the input mixer, use a DC block (refer to the 495/495P Service Manual,
Volume 2, or contact your local Tektronix Field Office or representative for
ordering information). It is important to be sure that all equipment being
tested has power applied through the line stabilizing networks before any RF
signal is connected to the spectrum analyzer input.
Connecting to a 75 O Source — Signals from a 75 Q source, at the
lower frequencies (1 MHz to 1 GHz), can be applied directly to the 75 Q
INPUT if Option 07 is installed. 75 Q signals may be applied to the 50 Q RF
INPUT by using a 75 Q-to-50 Q minimum loss attenuator (refer to the
Tektronix catalog or contact your local field office or representative for ordering information). A circuit diagram of a suitable matching pad for this purpose is shown in Figure 6-1.
6-2
Operation
Operation
Sensitivity and power levels are often rated in dBm (dB with reference to
1 mW regardless of impedance). Sensitivity and power levels for 75 Q systems are usually rated in dBmV (dB with reference to 1 mV across 75 Q).
Figure 6-2 shows the relationship between 50 Q and 75 Q units with matching attenuators included. The conversion to alternate reference level units is
listed below for 75 Q and is shown in Table 6-1 for 50 Q
dBmV (75 Q) = dBm (50 Q) +54.47 dB:
e.g. -60 dBm (50 O) + 54.47 dB = -5.5 dBmV (75 O)
dBm (75 Q) = dBm (50 Q) +5.72 dB:
e.g. -60 dBm (50 O) + 5.72 dB = -54.3 dBm (75 Cl)
NOTE
When the alternate 75 d input is used, the reference level readout
is correct for any units without additional conversions.
Amplitude Conversion — A conversion chart is shown in Figure 6-3. It
can be used to convert input signal levels of voltage or power to dBm, dBV,
dBmV, and dBuV.
Table 6-1: 50 O System Reference Level Conversion
To
From __
__
dBm
__
dBmV
__
__
dBuV
__
dBm________0__________+47_________+107____
495 & 495P User Manual
dBmV
-47
0
-60
dBuV
-107
+60
0
6-3
Operation
6-4
Operation
Operation
Resolution Bandwidth, Frequency Span, and Sweep Time
Resolution is the ability of the instrument to display discrete frequency
components within a frequency span. This ability is a function of the instrument bandwidth, sweep time, frequency span, and incidental FM.
Bandwidth also has an effect on the noise level. As the bandwidth decreases, the signal-to-noise ratio, or sensitivity, increases so that maximum
sensitivity is attained with the narrow resolution bandwidths.
As the spectrum analyzer sweep rate is increased, a critical rate is reached
where both sensitivity and resolution are degraded. Therefore, sweep time
for a calibrated display is dependent on the resolution bandwidth and frequency span.
In MAX SPAN mode, the display represents the full frequency range. The
frequency readout on the screen is indicated on the display by a frequency
dot if markers are off or by the primary marker if markers are turned on. This
frequency point will shift to center screen when the FREQUENCY SPAN/DIV
is reduced to some setting other than MAX. The FREQUENCY SPAN/DIV
setting depends on the particular measurement application. Wide spans are
usually used to monitor a frequency spectrum for spurious signals, or check
harmonic content. When wide spans are used for non-digital store displays,
the sweep rate is usually set for minimum flicker. This requires wider resolution bandwidths to maintain a calibrated display. Narrow spans are used to
analyze the characteristics about or near a particular signal, such as modulation side bands, bandwidth, or power line related distortion. Slow sweep
rates are required when using narrow spans and high resolution to observe
signal phenomena.
The 495/P will select the sweep rate and resolution bandwidth so the display
remains calibrated for the selected frequency span/division if TIME/DIV is in
the AUTO mode and AUTO RESOLN mode is on. AUTO RESOLN mode
optimizes bandwidth for the selected FREQUENCY SPAN/DIV and TIME/
DIV settings unless either is outside the range of calibration. When this
occurs, UNCAL lights and a > symbol prefixes the REFERENCE LEVEL
readout on the screen.
To analyze pulsed signals, a wider bandwidth than that provided by the
automatic feature is usually required. Set RESOLUTION BANDWIDTH to
approximately one-tenth the side lobe frequency width or the reciprocal of
the pulse width, if known, in order to ensure adequate bandwidth. The
resolution bandwidth is usually set for optimum main lobe detail after the
sweep rate has been selected.
Using the HELP Feature
When there is a question about the function of any front-panel push button
or control, press the [HELP] key; then press the push button or turn the
control in question. A message displayed on the screen describes the
function. The functions of all blue-labeled and green-labeled push buttons
can be called up without pushing the entire push button sequence each
time. Just push the appropriate [SHIFT] push button, push [HELP], and
push any of the push buttons as desired. For example, press [Blue-SHIFT]
495 & 495P User Manual
6-5
Operation
[HELP] [PLOT] to receive information about the PLOT feature. Because the
[Blue-SHIFT] push button was pressed when entering HELP mode, information about the CAL mode will be displayed when [FINE] is pressed.
CAL is the blue-shifted function of the [FINE] push button.
HELP mode will also provide explanations for the functions available from
the marker menu. For detailed instructions, see Using the Markers Feature
later in this section.
HELP mode is also useful in error detection (see Error Detection later in this
section).
Using the Signal Identifier
The 495/P features a SIGNAL IDENTIFY mode to help identify true signals
from false signals. When in this mode, the frequency of the local oscillators
are shifted on alternate sweeps. At the same time, the sweeps are vertically
displaced about two divisions. True signals shift only a small amount on
alternate sweeps, while false signals or spurious responses will shift at least
1 division.
This mode can only be activated when the FREQUENCY SPAN/DIV is
50 kHz or less.
Figure 6-4 illustrates two typical examples of signal identification. In Figure 6-4A, the signal remains at the same horizontal screen location for
alternate sweeps. This is a true response. A false signal may shift horizontal
screen location on alternate sweeps, or disappear from the screen as shown
in Figure 6-4B.
Using the Video Filters
The video filters restrict the video bandwidth so noise is reduced (see Figure 6-5). When signals are closely spaced, the filter can reduce the modulation between two signals to make it easier to analyze the display. The filters
can also be used to average the envelope of pulsed RF spectra that have a
relatively high pulse repetition frequency (prf). However, because the filter is
basically an integrating circuit, the video filter will not be very effective when
measuring low prf spectra.
The WIDE filter reduces the bandwidth to approximately 1/30th the selected
resolution bandwidth; the NARROW filter to approximately 1/300th. Using
the filter may require a reduction in the sweep rate to maintain a calibrated
display. UNCAL lights if the sweep rate is not compatible with the other
parameters to maintain a calibrated display. When either the WIDE or NARROW filter is selected, the filter bandwidth is displayed on the CRT lower
readout line.
6-6
Operation
Operation
495 & 495P User Manual
6-7
Operation
6-8
Operation
Operation
Using Time Domain Operation
When the FREQUENCY SPAN/DIV is zero, the 495/P functions as a tunable
receiver to display time domain characteristics within the selected resolution
bandwidth. Characteristics such as modulation pattern and pulse repetition
rates can now be analyzed with TIME/DIV selections. Resolution bandwidth
is usually maximum (3 MHz) for time domain analysis of the signal.
Triggering the Display
The TRIGGERING mode is usually FREE RUN for spectrum displays. However, it may be desirable or necessary to trigger the display when the event
is time related to some source, or when the frequency span has been reduced to zero for time domain analysis. In FREE RUN mode, the sweep will
not synchronize with any input signal.
In addition to FREE RUN mode, the sweep can be triggered internally (INT)
by the video signal, at the line frequency rate of the power supply (LINE), or
by an external signal (EXT) applied to the HORIZ|TRIG EXT IN connector
on the rear panel. The required amplitude for triggering is 2.0 divisions or
more for internal triggering and from 1.0 to 50 V maximum (DC + peak AC)
for external triggering.
In addition to the TRIGGERING source selections, SINGLE SWEEP mode is
provided. This mode is useful for viewing single events. In SINGLE SWEEP
mode, the sweep will run once after the circuit has been armed and a trigger
signal arrives. The READY indicator lights when the circuit is armed and
waiting to be triggered and remains lit during sweep time. Push [SINGLE
SWEEP] once to activate the SINGLE SWEEP mode and cancel the current
sweep. Push [SINGLE SWEEP] again to arm the trigger circuit so it is ready
for a trigger signal.
Sweeping the Display
Horizontal sweep voltage for the display can be internal or from an external
source. Sweep rate and source are selected with the TIME/DIV control.
When the TIME/DIV control is in the AUTO position, the sweep rate is
automatically set to maintain a calibrated display.
When TIME/DIV is in the EXT position, a signal source of 0 to +10 V applied
to the HORIZJTRIG EXT IN connector will sweep the CRT beam across the
10 division span. The input is DC coupled and sensitivity is 1 V/div. External
input impedance is approximately 10 kQ.
The beam can be manually positioned by the MANUAL SCAN control when
TIME/DIV is in the MNL position (see Manual Scan of the Spectrum that
follows).
Manual Scan of the Spectrum
The MANUAL SCAN control is usually used to examine a particular point or
sector of a display. One example is looking at one of the null points of a
frequency modulation spectrum. Another example is when it takes unneces-
495 & 495P User Manual
6-9
Operation
sarily long to look at a small segment of the full span because of the slow
sweep rate. With a wide FREQUENCY SPAN/DIV and/or a narrow RESOLUTION BANDWIDTH, it is very possible to manually scan too fast to achieve
an accurate display. Best results are obtained without digital storage. Digital
storage can produce unpredictable results due to the sweep rate, and the
digital storage display is only updated when scanning from left to right.
Reference Level, RF Attenuation, and Vertical Display
When a change is made to REFERENCE LEVEL, the gain distribution is
automatically selected (IF gain and input RF Attenuation) for the new refer-
ence level. The selection is made according to the settings of VERTICAL
DISPLAY, FINE, MIN RF ATTEN dB, and MIN NOISE/MIN DISTORTION.
The amount of input RF Attenuation set is based on the reference level
requested and the settings of MIN RF ATTEN dB and MIN NOISE/MIN
DISTORTION. The 495/P assumes the MIN RF ATTEN dB selection is the
minimum attenuation required for the expected signal levels, and will not
reduce RF Attenuation below this value. As MIN RF ATTEN dB is increased,
the lowest reference level is raised an equal amount. At 0 dB minimum
attenuation, the lowest reference level is -117 dBm; at 10 dB minimum
attenuation, the lowest reference level is -107 dBm, and so on. The best
ratio of RF Attenuation to IF gain is selected according to the MINIMUM
NOISE/MINIMUM DISTORTION mode (see the description later in this
section).
The REFERENCE LEVEL control steps depend on the VERTICAL DISPLAY
mode and FINE mode settings. With LOG mode selected, the REFERENCE
LEVEL control steps in 1 dB to 15 dB increments if FINE mode is off. With
FINE mode on, the REFERENCE LEVEL control steps in 1 dB increments
for display factors of 5 dB/div or more, and 0.25 dB for display factors of
4 dB/DIV or less. The 0.25 dB increments apply to the Delta A mode (see
the description later in this section).
With LIN mode selected and FINE mode off, the bottom of the CRT graticule
is zero volts, and the top of the CRT graticule is eight times the vertical
display factor. The display factor changes in a 1 -2-5 volts/division sequence from 500 mV to 50 nV with FINE mode off. With FINE mode on, the
reference level changes in 1 dB steps and the scale factor/division is oneeighth the voltage equivalent of the REFERENCE LEVEL setting.
Alternate Reference Level Units Selection
To select an alternate to dBm reference level units, press [Blue-SHIFT]
[REF LEVEL UNITS]. This sequence enters the reference level units menu.
Now select one of the four available selections:
6-70
•
[0] selects dBm
•
[1] selects dBv
•
[2] selects dBmV
•
[3] selects dBuV
Operation
Operation
The 495/P automatically converts the REFERENCE LEVEL readout for the
new units. For example, a readout of 0 dBm changes to -13 dBV when dBV
units are selected from the menu.
Using the Delta A Mode
To select the Delta A mode, push [FINE] while the VERTICAL DISPLAY
factor is 4 dB/Div or less. The REFERENCE LEVEL readout goes to 0.00
dB and the REFERENCE LEVEL control steps in 0.25 dB increments from
this reference.
The Delta A mode accurately measures signal-relative amplitude difference.
This is possible because the gain distribution (IF gain and RF Attenuation)
does not change in the Delta A mode. The REFERENCE LEVEL setting is
changed by shifting the log amplifier offset. The total range of the Delta A
mode is 57.75 dB. The measurement range depends on the REFERENCE
LEVEL setting that is current at the time the Delta A mode is activated. It is
typically at least 0 to 48 dB below the REFERENCE LEVEL setting that was
current at the time the Delta A mode was activated. The overall instrument
reference level range of -117 dBm to +50 dBm cannot be exceeded.
The Delta A mode is turned off when the VERTICAL DISPLAY factor is
increased above 4 dB/Div, when FINE mode is turned off, or when the gain
distribution is changed with the MIN RF ATTEN dB or MIN NOISE selections.
Signals with large amplitude differences that are within the Delta A range
can be compared without the distortion usually introduced when signals are
driven off-screen. Signals shifted off-screen by changes in the Delta A reference level are not over-driving the input. This is because the RF Attenuator
and IF gain do not change. Thus, the mixers do not see any change in
signal levels even though the Delta A reference level changes.
Follow these steps to measure the amplitude level difference between two
signals using the Delta A mode:
1. Press [FINE] to select the Delta A mode.
2. Select a VERTICAL DISPLAY factor of 4 dB/Div or less with the dB/DIV
DATA ENTRY push buttons, or press the [2 dB/DIV] push button.
3. Set the REFERENCE LEVEL control to position the peak of the larger
signal to a graticule line.
4. Press the [FINE] push button twice to reset the readout to 0.00 dB.
5. Use the REFERENCE LEVEL control to set the peak of the lower amplitude signal to the same graticule line established in step 3.
6. The REFERENCE LEVEL readout will now indicate the amplitude difference between the two signals in dB.
NOTE
Do not confuse the Delta A mode with the delta marker mode.
495 & 495P User Manual
6-11
Operation
Using MIN NOISE, MIN DISTORTION, or REDUCED GAIN
Mode
One of three methods can be selected to control RF Attenuator and IF gain
settings. MIN NOISE mode minimizes noise level by decreasing input attenuation and IF gain by 10 dB. MIN DISTORTION mode minimizes input mixer
overload by increasing input attenuation and IF gain by 10 dB.
The REDUCED GAIN mode uses the identify offset to reduce the effective
gain of the 495/P, which lowers the displayed noise level. Because identify
offset is one division, and because the RF Attenuator is controllable in 10 dB
steps, the REDUCED GAIN mode can only be selected when the VERTICAL
SCALE factor is 10 dB/Div.
The REDUCED GAIN mode reduces the IF gain and RF Attenuation by
10 dB for any REFERENCE LEVEL setting for which the RF Attenuation (in
non-REDUCED GAIN mode) is at least 10 dB greater than the MIN RF
ATTEN dB control setting.
With MIN NOISE mode on and MIN RF ATTEN dB set to 60 dB, the REFERENCE LEVEL can be set to +40 dBm. Do not increase input signal level
to full screen with a REFERENCE LEVEL of +40 dBm because this will
exceed the RF Attenuator rating.
In the REDUCED GAIN mode, the REFERENCE LEVEL may be set to
+40 dBm (with MIN DISTORTION mode on) or +50 dBm (with MIN NOISE
mode on). However, the maximum input level of the 495/P is still +30 dBm.
NEVER apply more than +30 dBm to the input of the 495/P at any time,
regardless of the indicated level.
REDUCED GAIN mode is selected from the SPECIAL MODES Menu (press
[Blue-SHIFT] [VIDEO FILTER WIDE] [2]. Menu item [2] toggles the
REDUCED GAIN mode from off to on, or on to off, each time it is selected.
The REDUCED GAIN mode is indicated by an R located at the top right
corner of the screen. (If an error message is displayed, the R will not appear
on the screen.)
The REDUCED GAIN mode can be used with either MIN DISTORTION or
MIN NOISE modes. When MIN DISTORTION mode is 13turned on, the
REDUCED GAIN mode effects the display in a manner that is similar to
activating the MIN NOISE mode (noise decreases by 10 dB). When MIN
NOISE mode is active, the REDUCED GAIN mode will further increase the
distortion. Also, on-screen compression may occur. For this reason, any
digital storage data that appears above the top of the viewing area (that is,
data values of 225 to 250, above the top graticule line) is likely to be inaccurate.
If the IDENTIFY mode is used when REDUCED GAIN mode is active, the
identify (alternate) sweep is moved up one division on the screen. It is
normally moved down one division.
6-12
Operation
Operation
Using Digital Storage
Digital storage provides a smooth, flicker-free display. Two complete displays can be digitized and stored. In addition, the STORE DISPLAY and
RECALL functions will store up to nine displays in memory (see Using the
Store and Recall Features later in this section). One of the two digitized
waveforms can be saved and then compared to later waveforms. The MAX
HOLD feature updates digital storage data only when the input signal amplitude is greater than previous data. This allows monitoring and graphic
plotting of display changes (amplitude and frequency) with time.
The display is divided by a horizontal line that is positioned with the PEAK/
AVERAGE control. Above the line, video information is peak detected; below
the line, signal averaging occurs. This feature subdues noise in the portion
below the line and allows full peak detection above the line. An intensified
spot on the line indicates the horizontal position where memory is being
updated. The average (number of samples) is a function of the sweep rate;
the slower the rate the more samples.
The digital storage display is divided into an A and B section. Data can be
stored in either A or B or in both. There are 500 horizontal locations in A and
500 horizontal locations in B. When both are displayed, the origin of the B
waveform is shifted so the A and B coordinates are interlaced to provide
1000 display increments. Data in memory is continually updated with each
sweep so the display is always current.
SAVE A Mode — When SAVE A mode is turned on, data in the A section is
saved and only the B section of storage is updated. This takes place whether the A waveform is displayed or not. This mode captures an event or
waveform, with its readout, for comparison with a subsequent event displayed by the B display. If VIEW B is on, the readout applies to the current B
waveform. If SAVE A and VIEW A are on and VIEW B and B-SAVE A are off,
the readout applies to the saved A waveform.
B-SAVE A Mode — When B-SAVE A mode is turned on, the arithmetic
difference between the B waveform and the saved A waveform is displayed
(see Figure 6-6). This convenient mode can be used to align filters or other
devices. The reference waveform is stored in A and the unknown is displayed by B. The reference level is usually set mid-screen so positive and
negative quantities can be observed. The position of the zero reference can
be changed by an internal switch. Contact qualified service personnel to
have the reference level repositioned.
MAX HOLD Mode — MAX HOLD mode causes the memory to be updated
only if the new input is of higher magnitude than the former (B memory only
if SAVE A is active). This allows monitoring of signals that may change with
time and provides a graphic record of amplitude/frequency excursions.
495 & 495P User Manual
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Operation
Signal averaging is useful for suppressing noise. The number of samples
averaged per horizontal digitized slot is a function of the 495/P sweep rate.
The slower the sweep speed, the more samples averaged per horizontal
slot. RESOLUTION BANDWIDTH affects the amplitude difference between
peak detected and average levels of CW signals. When the RESOLUTION
BANDWIDTH is less than 1730th the FREQUENCY SPAN/DIV (e.g., 100 kHz
or less with 5 MHz FREQUENCY SPAN/DIV) there will be significant error in
the average amplitude levels of CW signals, especially if only A or B is
displayed. The peak value will be the true value. When using narrow RESOLUTION BANDWIDTH with wide frequency spans, it is best to run digital
storage with both the A and B waveforms interlaced and the cursor (horizontal line) at the bottom of the display.
To measure signal amplitude level, set the cursor to the bottom of the
screen. To average noise, set the horizontal line at least one division above
the noise level.
Using the Store and Recall Features
The 495/P features two functions to store up to nine waveforms, with marker(s) and readout, in memory to be recalled later for review or analyses. To
save the display currently on the screen, press [Blue-SHIFT] [STORE
DISP], the register number ([0] - [8]) where you want to store the display,
and if SAVE A mode is on, the identity of the display you want stored (A or
B). To later recall this same display, press [Blue-SHIFT] [RECALL], and
the register menu showing the center frequency of each stored display will
6-74
Operation
Operation
appear on the screen. Select the correct register number with a DATA
ENTRY push button, and then select the part of the digital storage (A or B)
where you want to place the recalled display.
SAVE A mode is automatically turned on to prevent an overwrite. If location
A is selected, VIEW A must be on to see the recalled display, and VIEW B
must be off to see the readout that applies to the recalled display.
If VIEW B and VIEW A are on, both the display recalled in A and the current
display in B will be visible on the screen. The readout shown applies to the
current B display. Turn VIEW B off to see the readout that applies to the
recalled A display.
If location B is selected, the next sweep will overwrite the display unless
SINGLE SWEEP mode was activated before selecting B. A message will
appear on the screen as a reminder of this. VIEW B must be on to observe
the recalled display. Remember to turn SINGLE SWEEP mode off when
leaving this recalled mode.
Plotting the Display
Press [PLOT] (495) or [Blue-SHIFT] [PLOT] (495P) to drive many external
plotters such as those listed below:
•
Tektronix HC 100
•
Tektronix 4662 Option 01
•
Tektronix 4662 Option 31
•
Tektronix 4663 (emulating the 4662)
•
Hewlett-Packard HP7470A
•
Hewlett-Packard HP7475A
•
Hewlett-Packard HP7580B
•
Hewlett-Packard HP7585B
•
Hewlett-Packard HP7486B
•
Gould 6310
•
Gould 6320
To use the plot feature, connect the plotter to the 495/P with an
IEEE STD 488 (GPIB) cable, and complete the following steps:
1. Set the corners of the plot for a 3:2 aspect ratio for the Tektronix plotters,
or 6:5 for the Hewlett Packard and Gould plotters. The plotter must be in
the Listen Only mode. On the 495P, the TALK ONLY switch on the rearpanel GPIB ADDRESS switch bank must be closed or in the 1 position.
2. Set the plotter interface switches as follows:
Tektronix HC 100:
Address = 31
495 & 495P User Manual
6-15
Operation
Tektronix 4662 Option 01 or 4662 Option 31 (rear panel):
A = 0, 1,8, or 9
B = C or D
C = X (does not matter)
D = X (does not matter)
Tektronix 4663:
Interface Select = 1 if Option 04 or 2 if Option 01
Initial Command/Response Format = 5
Interface Mode = Listen Only
Hewlett-Packard or Gould Plotters:
Address = 31
3. Press [Blue-SHIFT] [SAVE A] on the 495/R and select the desired
plotter type from the displayed menu. The selection is stored in memory
and does not need to be selected again unless the plotter type is
changed.
4. Select the display and the information that you wish to plot. The PLOT
feature is similar to using a camera. The plot includes everything that is
turned on for the CRT display. The information plotted depends on the
setting of several front-panel push buttons and controls:
• If READOUT is on, the CRT readout will be plotted with the display.
•
If GRAT ILLUM is on, the bezel and graticule information will be
included with the plot.
•
If VIEW A, VIEW B, or B-SAVE A are on, these waveforms will be
part of the plot (if any of these functions are off, they will not be
plotted).
The zero level for a B-SAVE A waveform is usually the graticule center line.
(Switches within the instrument can set the level. Contact your service
personnel for this change.) If you desire to shift the zero level for the plotting
function only, press [Blue-SHIFT] [B-SAVE A], and enter the desired level
in display units (25 is the bottom graticule line, 25 units/div). This zero level
is retained in memory. It is not related to the display zero level, since the
processor has no way of determining the internally-set zero level for the
screen and no way to change it.
Using the Markers Feature
The marker modes provide direct readout of frequency and amplitude
information of any point along any displayed trace. Relative (delta) frequency and amplitude information between any two points along any displayed
trace or between traces is also available. Two independent marker frequencies and amplitudes cannot be displayed at the same time.
Marker Terms — The following definitions of marker terms are used
throughout this section.
6-76
Operation
Operation
Live Trace — Any combination of the A trace when SAVE A is off and/or
the B trace. A trace recalled into B is not an active trace.
Active Trace — Any combination of the A trace when SAVE A is off
and/or the B trace; or, the B-SAVE A trace. A trace recalled into B is not
an active trace.
Inactive Trace — Either a SAVE A trace or a trace recalled into the B
display before the sweep is started.
Primary Marker — The marker displayed in the Single Marker mode
whose frequency and/or position is changed when tuning with the
CENTER/MARKER FREQUENCY control. When two markers are displayed, the brightest marker is the Primary marker.
Secondary Marker — The "second" marker; displayed only in the Delta
Marker mode.
Marker Turn On —The Single Marker mode places one marker (Primary
marker) on the spectrum to display marker frequency and amplitude. The
Delta Marker mode places two markers (Primary marker and Secondary
marker) that display the difference in frequency and amplitude between the
two markers. When two markers are displayed, the Primary marker is brighter. The Primary marker position and frequency can be changed with the
CENTER/MARKER FREQUENCY control or from the GPIB.
The marker(s) can be turned on by pushing many of the push buttons
related to marker action. Here are some examples:
•
[TUNE CF/MKR] (push button lit) turns on the Primary marker
•
[Blue-SHIFT] [MKR -» CENTER] turns on the Primary marker
•
[Green-SHIFT] [PEAK FIND] turns on the Primary marker
•
[Green-SHIFT] [SIGNAL TRACK] turns on the Primary marker
•
[Green-SHIFT] [MKR -» REF LVL] turns on the Primary marker
[Green-SHIFT] [1« -MKR->2] turns on both the Primary and Secondary markers
•
[Green-SHIFT] [A MKR] turns on both the Primary and Secondary
markers
There are three push button sequences that turn the marker(s) off:
495 & 495P User Manual
•
[Blue-SHIFT] [MKR OFF] turns off all marker functions
•
[Blue-SHIFT] [INIT] turns off all marker functions (the instrument is
returned to the initial turn-on condition)
•
[Green-SHIFT] [A MKR] (when both markers are on) turns off the
Secondary marker and returns the instrument to the Single Marker
mode
6-17
Operation
The markers are visible only when DIGITAL STORAGE functions are on;
there can be no markers on a real-time trace. When a trace with a marker or
markers is stored, the marker positions and frequencies are also stored.
When the trace is recalled and the marker system is on, the marker(s) first
appears at the stored locations(s). Therefore, there is greater accuracy than
is normally possible on an inactive trace. This is especially true if the stored
marker frequency was the result of a signal count. The increased accuracy
is lost as soon as the marker is tuned.
In either the Single or Delta marker mode, a second line of readout appears
at the top of the screen. In the Single Marker mode, the marker frequency
readout is displayed directly below the center frequency readout, and the
marker amplitude is displayed directly below the reference level readout. In
the Delta Marker mode, the frequency of the Primary marker with respect to
that of the Secondary marker is displayed directly below the frequency
readout, and the amplitude of the Primary marker with respect to that of the
Secondary marker is displayed directly below the reference level readout.
When in the Delta Marker mode, the relative amplitude and frequency
readouts are enclosed on the screen in parentheses. If the marker amplitude
is outside the digital storage range, OVER or UNDER is displayed in the
amplitude readout field.
Marker Menu and Assign Menu — Most of the marker functions are
available directly from front-panel push button sequence*. There are additional marker functions that are available either by direct selection from the
Marker Menu, or after they have been assigned from the Assign Menu to
either the [ASSIGN 1] or [ASSIGN 2] push button. Press [MARKER
MENU] to show a list of additional marker functions. These functions are all
available simply by selecting them with the correct DATA ENTRY number
push button (see Marker Functions in Section 4 for the description of these
functions).
Follow these steps to assign a function to the [ASSIGN 1] or [ASSIGN 2]
push button. (Once a function has been assigned, it will remain until the
push button is assigned a different function.)
1. Press [MARKER MENU] to show a list of additional marker functions.
2. Select [6] ASSIGN FUNCTION TO KEY This will bring up the Assign
Menu that contains the functions that can be assigned.
3.
Push the correct DATA ENTRY number push button.
4. For menu items 0, 1, 2, 3, or 6:
a. The two [ASSIGN] push buttons will light.
b. A message will appear that asks you which push button you want to
use for that function.
c. Push the desired push button,
d. The assignment has been made.
6-78
Operation
Operation
5. For functions 4 or 5
a. A message prompts you to enter the amount you want the marker to
move.
b. Enter the amount and units selection,
c. The two [ASSIGN] push buttons will light.
d. A message will appear that asks you which push button you want to
use for that function.
e. Push the desired push button,
f.
The assignment has been made.
Once a function has been assigned, you can get a description of the function by pressing [Green-SHIFT] [HELP] and the correct [ASSIGN] push
button.
Assigning Markers — When the marker mode is first turned on from the
front panel, the trace(s) on which the marker(s) appears is determined by
the traces that are currently displayed, as indicated in Table 6-2. When a
trace is turned off, any marker(s) on it is re-located according to Table 6-2.
When a trace is turned on, the previous marker locations do not change;
except, the marker always jumps to the active trace in maximum span or
when in the SIGNAL TRACK mode.
Table 6-2: Marker Trace Organization
VIEW A
VIEWB
SAVE A
B -SAVE A
Primary
Marker On
Secondary
Marker On
Off
Off
Off
Off
Full3
Full3
Off
Off
On
Off
Aa
Aa
Off
Off
On
On
B- SAVE A
B-SAVE A
Off
On
Off
Off
Full
Full
Off
On
On
Off
B
B
Off
On
On
On
B
B
On
Off
Off
Off
Full
Full
On
Off
On
Off
A
A
On
Off
On
On
B-SAVE A
B-SAVE A
On
On
Off
Off
Full
Full
On
On
On
Off
B
A
On
On
On
On
B
A
a
Not applicable. Since no digital storage traces are being viewed, there is no visible marker. The listed trace is that for which marker
readouts are given.
495 & 495P User Manual
6-79
Operation
Tuning Markers — Move the Primary marker with the front-panel CENTER/MARKER FREQUENCY control (when the [TUNE CF/MKR] push
button is lit). To make it possible to change the position of the Secondary
marker, you must make the Secondary marker be the Primary marker. Push
[Green—SHIFT] [1<— MKR—>2] to swap the Primary and Secondary marker
positions. Move the Primary marker (which used to be the Secondary marker), and then push [Green-SHIFT] [1<-MKR-»2] again to swap the Primary marker back to its previous location.
The marker normally moves over the fixed display. Marker tuning (both
frequency and position) stops when the screen edge is reached while using
the CENTER/MARKER FREQUENCY control.
The marker tuning rate depends on the speed with which the CENTER/
MARKER FREQUENCY control is turned. If the control is turned rapidly, the
marker moves 1/10 of a division per increment. If the knob is turned quite
slowly, the marker moves 1/100 of a division per increment. At intermediate
turning speeds, the marker moves approximately 1/30 of a division per
increment.
When two markers are displayed (delta-marker mode), and the marker
frequency, center frequency, and span are changed, the Secondary marker
remains fixed at its original frequency and is allowed to move off the screen.
If the Primary and Secondary markers are swapped (with the [GreenSHIFT] [1<-MKR->2] push button) while the Secondary marker is off the
screen, the display is centered on the frequency of the old Secondary
marker (now the new Primary marker). The old Primary marker (now the
new Secondary marker) is placed off the screen.
Error Detection
When an internal error is found in the 495/P, the words ERROR USE HELP
will flash one after the other at the top, right corner of the screen (a steady
ERROR message will appear when under remote control). This message
appears when the markers are on or the instrument is in MAX SPAN mode.
Press [HELP] to read the definition of the problem and the probable effects
of the problem. If the markers are off and the measurement is not in MAX
SPAN mode, the error message will be steady and will specify the problem
area. Additional information and servicing instructions are in the diagnostics
information in Section 6, Maintenance in the Service Manual, Volume 1. If
you cannot solve the problem with the HELP information, report all problems
or error information to qualified service personnel.
Using the Automatic Performance Testing Feature
The push button sequence [Blue-SHIFT] [CAL] activates a routine that
tests frequency and relative amplitude of the IF filters. This routine should be
done any time the temperature changes. Settings are held in memory after
the test routine has run. Refer to Display Parameter Controls in Section 4 for
more details.
6-20
Operation
Operation
Using the Tracking Generator Mode
In order to obtain higher frequency accuracy when using the tracking generator, the TRACKING GENERATOR mode disables use of the frequency
correction factors for all resolution bandwidth filters wider than 10 kHz.
These wide filters may be centered too far from 10 MHz for the difference to
be corrected with the Tracking Adjust control on the tracking generator.
All amplitude correction factors are always used.
For maximum frequency and amplitude accuracy, always adjust the Tracking
Adjust control to peak the response in the resolution bandwidth filter you are
using. Remaining amplitude errors can be corrected by using the B-SAVE
A mode of digital storage.
Use the [Blue-SHIFT] [VIDEO FILTER WIDE] push button sequence to
enter the SPECIAL MODES Menu. Press [0] to select TRACKING GENERATOR mode (select it again to turn it off). When the TRACKING GENERATOR
mode is on, a T appears at the top right corner of the screen unless an error
message is being displayed.
Using the Sideband Analyzer Mode
Since the 1405 Sideband Analyzer only uses the first local oscillator of the
495/P, it is only useful when the first local oscillator is sweeping (not phase
locked). The SIDEBAND ANALYZER mode extends the usefulness of the
1405 by causing the 495/P to phase lock in 50 kHz/Div instead of the normal
200 kHz/Div.
Use the [Blue-SHIFT] [VIDEO FILTER WIDE] push button sequence to
enter the SPECIAL MODES Menu. Press [1] to select SIDEBAND ANALYZER
mode (select it again to turn it off). When the SIDEBAND ANALYZER mode is
on, an S appears at the top right corner of the screen unless an error mes-
sage is being displayed.
Using the EOS Correction Mode
The instrument normally measures the drift rate of its oscillators and corrects
them when needed to maintain specified accuracy. When the EOS
CORRECTION mode is on, the oscillators are corrected at the end of every
sweep.
Use the [Blue-SHIFT] [VIDEO FILTER WIDE] push button sequence to
enter the SPECIAL MODES Menu. Press [3] to select EOS CORRECTION
mode (select it again to turn it off). When the EOS CORRECTION mode is
on, an E appears at the top right corner of the screen unless an error message is being displayed.
Using the Time Measurement Feature
The 495/P employs a special time measurement feature that is available
when the instrument is in the ZERO SPAN mode, with either one or two
markers on.
495 & 495P User Manual
6-27
Operation
Use the [Blue-SHIFT] [VIDEO FILTER WIDE] push button sequence to
enter the SPECIAL MODES Menu. Press [4] to select ZERO-SPAN TIME
mode (select it again to turn it off). When the ZERO-SPAN TIME mode is
on, a Z appears at the top, right corner of the screen unless an error message is being displayed.
In the ZERO-SPAN MODE, the marker frequency readout or delta-marker
frequency readout is replaced by a time or delta time readout, respectively.
The time readout in the single-marker mode is the time to the marker position from the trigger point. This point is 1/2 division to the left of the screen.
In the Delta Marker Mode, the delta time readout gives the time difference
between the two markers. In both cases, the time value is scaled from the
marker position(s) and the time/division. No actual time measurement is
done.
The time measurement feature is available only during certain timing conditions. If the TIME/DIV setting is MNL EXT, or is faster than 1 ms/Div, the
message TIME UNAVAILABLE is displayed in the location of the normal
readout.
When in the DELTA TIME READOUT mode, both markers must be on the
same trace for time measurement. If the markers are on different traces
when ZERO SPAN mode is entered, the secondary marker will move to the
trace of the primary marker. (This marker will not move back when leaving
zero span.) When either marker is assigned to a new trace, both markers
(assuming delta markers are on) will move together.
In frequency-mode marker operation, the secondary marker remains at a
constant frequency, while the primary marker remains at a constant horizontal location. However, in the TIME mode, both markers remain at constant
horizontal positions as the sweep speed is changed.
Most of the frequency-related marker functions remain frequency-related in
ZERO SPAN mode. The [Green-SHIFT] [STEP SIZE] push button still
defines the frequency step size for the marker or delta marker.
In the tune marker mode, [Blue-SHIFT] [FREQ] and the DATA ENTRY
push buttons will enter marker time. If the TIME UNAVAILABLE message is
displayed, the entry functions will be disabled.
The [Blue-SHIFT] [MKR -» CENTER] push button function is not available
in ZERO SPAN mode.
BANDWIDTH and SIGNAL TRACK modes will go to idle in ZERO SPAN
mode. Since the idle message appears in the frequency/time readout location, these functions are turned off so the time display can appear on the
screen.
6-22
Operation
Operation
Programming
Features (495P GPIB
Operation)
Setting GPIB Address Switches
The general purpose interface bus (GPIB) ADDRESS switches on the rear
panel set the value of the instrument's GPIB address. The 495P Programmer manual contains details of how the switches are used in remote control
operations.
The switches can be set as desired, except when using Tektronix 4050-Series controllers. They reserve address 0 for their own use. Selecting a primary address of 31 logically removes the instrument from the bus. With
address 31 selected, the 495P does not respond to any GPIB address, but
remains both unlistened and untalked. If the switches are changed after
power-up, the [RESET TO LOCAL] or [Blue-SHIFT] [PLOT] push button
must be activated so the 495P will update the primary address.
TALK ONLY, LISTEN ONLY Switches
The switches for talk-only and listen-only operation are part of the GPIB
ADDRESS switch bank on the 495P rear panel. Set either or both switches
as needed (you can have talk only, listen only, or both talk only and listen
only features). If the 495P power is on, press [RESET TO LOCAL] or
[Blue-SHIFT] [PLOT] to implement changes to the switch settings. Both
the TALK ONLY and LISTEN ONLY switches must be off (down) when the
495P is used with any controller.
Set the LF OR EOI switch to EOI (down) for use with Tektronix equipment.
The switches marked 1, 2, 4, 8, and 16 may be set to any combination
except all ones (decimal 31), which logically disconnects the 495P from the
bus, or all zeroes when using the instrument with a 4050-Series controller.
Connecting to a System
Connect the 495P to a GPIB system through the GPIB cable supplied with
the instrument. Connect the cable after the power to the 495P has been
turned on, or the controller is turned off, to avoid generating interference on
the bus.
Personalized Macros
The 495P allows you to personalize your instrument to fill your specific
needs. Eight programs compiled by you to your specifications can be stored
in memory to be called up and run at any time. This feature makes it possible for you to perform complete tests with only the 495P; without the need
of a controller. These unique programs made up of existing, prepared commands are macroinstructions (macros).
The dictionary definition of a macro is "a single computer instruction that
stands for a sequence of operations." Most of the commands available with
the 495P can be used in macros.
495 & 495P User Manual
6-23
Operation
There is 8K of memory reserved for personalized macros (the MEMORY
query in the Macros section of the 495P Programmer manual describes
how to find out how much memory is available). When you create the macro, you have 22 characters available to you for the definitive names. Refer to
the 495P Programmer manual for the available commands and their use,
the amount of memory needed for each usable command, examples, and
sample macros.
Operational
Considerations and
Precautions
Following are some operational precautions to observe and traps that can
occur when analyzing displays.
RF INPUT Power Limit
CAUTION — DO NOT EXCEED THE RF INPUT POWER LIMIT OF +30 DBM.
DO NOT APPLY DC VOLTAGE TO THE RF INPUT.
Instrument Warm-up After Storage
After storage below -15° C, allow 15 minutes instrument warm-up time,
then turn the power off and back on.
Auto Resolution
Use AUTO RESOLN mode with care when measuring absolute amplitude
level. Always use a bandwidth wider than the incidental FM of the signal
source.
Level of Pulsed Signals
The spectrum for a pulsed signal is spread out. Consequently, the height of
the displayed response is less for a pulsed signal than for a CW signal of the
same peak amplitude. This loss in display height means, in effect, a loss in
sensitivity. The amount of loss can be computed from the following formula:
Voltage loss = (t0B)(1.5)
where to = pulse duty cycle
B = resolution bandwidth
The power of the self-generated noise increase is proportional to bandwidth.
Pulsed RF voltage level is also proportional. Since power is proportional to
voltage squared, a wider bandwidth gives better sensitivity and greater
dynamic range for pulsed RF inputs.
When in doubt about signal level overdrive problems, reduce the signal level
by inserting RF attenuation; then, repeat the measurement. If the two agree,
the measurement is correct. If not, the input mixer stage is probably overdriven.
6-24
Operation
Operation
An important consideration for pulsed RF measurements is the peak signal
level at the mixer. The signal level is greater by (t0B)(1.5) than the peak level
displayed on the screen. Taking the sensitivity loss into account is the only
way of being sure that the mixer peak power input for linear operation is not
exceeded.
Level of Continuous Wave Signals
Problems similar to those described in Level of Pulsed Signals can occur
when analyzing CW signals at relatively narrow span widths. The large CW
signal may not appear on screen because its frequency is outside the set
span width. The mixer, nevertheless, is saturated and will compress signals.
Excessive Input Signal Level
Too much input power will destroy the front-end mixer or RF Attenuator.
Replacement mixers and attenuators are costly. When working with high
power signals, use couplers or other devices to reduce the signal down to
acceptable levels. Once the signal is below the rating of the RF Attenuator,
prevent possible mixer damage by setting the MIN RF ATTEN dB control
fully clockwise; then reduce attenuation if needed.
No CRT Trace
The push button sequence [Blue-SHIFT] [BASELINE CLIP] is used to
reduce the brightness of the baseline on the screen for easier viewing of the
readout. If TRIGGERING, INTENSITY, and Vertical POSITION seem to be
set properly and there is no CRT trace, check the status of the [BlueSHIFT] [BASELINE CLIP] mode. The trace may be turned off.
PEAK/AVERAGE
The PEAK/AVERAGE control is normally set fully counterclockwise so
narrow signals in wide spans are not reduced in amplitude.
Digital Storage Effects on Signal Analyses
When using digital storage, the frequency base is divided into storage slots.
For peak displays above the cursor (horizontal line) the display point in each
slot corresponds to the maximum sampled value of the signal. Samples are
taken at about 9 us intervals. When sweeping at one second per division,
this is about 1000 samples per slot. For average displays below the cursor,
the values of all samples per slot are added and divided by the number of
samples to compute the display point for each slot. Each display point is
connected to create a smooth display. When A or B memory are displayed
independently, only half of the slots are connected. The following situation
may affect measurements made when using the digital storage display.
495 & 495P User Manual
6-25
Operation
If the cursor set by PEAK/AVERAGE is above the signal level, the average
value for each digital slot will be displayed. With narrow resolution bandwidths compared to the slot width, the average value of the resolution response shape will be displayed. The resulting display will not represent the
true signal amplitude.
To avoid this situation, run digital storage with A and B interlaced. Do not set
the PEAK/AVERAGE cursor to average a CW signal. It is best if the cursor is
about 1/4 division above the signal to be averaged, and about 1/2 division
below the signal to be analyzed.
These restrictions do not apply when the resolution bandwidth is wide
compared to a digital storage slot (e.g., 5 MHz FREQUENCY SPAN/DIV with
1 MHz RESOLUTION BANDWIDTH).
Stored Display Averaged in Wide Spans
When operating in wide spans with digital storage, low-level signals will be
averaged with the noise and lost if the PEAK/AVERAGE cursor is above the
display. Turn the control fully counterclockwise for peak detection when
operating with wide spans.
Automatic Calibration of Relative Amplitudes of Resolution
Bandwidth Filters
If a MEASUREMENT FAILED message appears when the automatic calibration completes, refer to the correction factors for an explanation. Press
[Blue-SHIFT] [LIN] to display the correction factors held in memory. Refer
to Display Calibration in Section 5 for further information.
Triggering
The TRIGGERING mode is set to FREE RUN for most applications. In
pulsed RF applications, a triggered display is required to measure between
pulse repetition lines to determine the pulse repetition rate.
Internal triggering requires two or more divisions of signal amplitude. Tune
the CENTER/MARKER FREQUENCY control to position a signal of two
divisions or more at the sweep start (left edge of the screen) before changing the trigger source from FREE RUN to INT.
6-26
Operation
Operation
Service Information
Service Manual
The 495/P service manuals are separate publications. The 495/495P Service Manual, Volume 1 includes circuit descriptions, troubleshooting information, calibration procedures, and maintenance procedures. The
495/495P Service Manual, Volume 2 includes the electrical and mechanical
parts lists, standard and optional accessories, and schematic diagrams.
WARNING
Service manuals are intended for use by QUALIFIED SERVICE
PERSONNEL ONLY. To avoid electrical shock, DO NOT perform any
servicing unless qualified to do so. Service personnel should read
the Safety information at the beginning of the service manuals
before performing any servicing.
Product Service
To assure adequate product service and maintenance for our instruments,
Tektronix, Inc. has established Field Offices and Service Centers at strategic
points throughout the United States and in all other countries where our
products are sold. Contact your local Service Center, representative, or sales
engineer for details regarding warranty, calibration, emergency repair, repair
parts, scheduled maintenance, maintenance agreements, pickup and
delivery. On-Site Service for fixed installations and other services are available through these centers.
Emergency Repair
This service provides immediate attention to instrument malfunction if you
are in an emergency situation. Contact any Tektronix Service center for
assistance to get you on your way within a minimum amount of time.
Maintenance Agreements
Several types of maintenance or repair agreements are available. For example, for a fixed fee, a maintenance agreement program provides maintenance and calibration on a regular basis. Tektronix, Inc. will remind you
when a product is due for calibration and perform the service within a specified time-frame. Refer to Options M1 through M9 in Section 7, Options, for
extended service and warranty options available. Any Service Center can
furnish complete information on costs and types of maintenance programs.
495 & 495P User Manual
6-27
Operation
6-28
Operation
This section describes the options available at this time for the spectrum
analyzer. Changes in specifications, if any, are described in this section.
Contact your local Tektronix Field Office or representative for additional
information and ordering instructions (unless otherwise indicated).
Options are usually factory installed; however, field kits are available for
some options. Contact your local Tektronix Field Office or representative for
information on field kits and their installation.
Options M1, M2, M7,
M8, and M9
(Extended Service
There are six extended service and warranty options offered for the 495P
(see Table 7-1) that go beyond the basic one-year coverage. Contact our
local Tektronix Field Office or representative for additional information to
satisfy your specific requirements.
and Warranty
Options)
Options A1, A2, A3,
A4, and A5 (Power
Cord Options)
495 & 495P User Manual
Table 7-1: Extended Service and Warranty Options
Option
Description
M1
2 years service and 2 calibrations
M2
4 years service
M3
4 years service and 4 calibrations
M7
2 calibrations
M8
4 calibrations
M9
2 years service
There are five international power cord options offered for the spectrum
analyzer (see Table 7-2). For ordering purposes, refer to the Replaceable
Mechanical Parts list in the 495/495P Service Volume 2, for the Tektronix
Part Number.
7-1
Options
7-2
Options
Options
Option 07 provides a 75 Q input in addition to the standard 50 Q input.
Table 7-3 lists the changes and additions to the standard electrical characteristics. These characteristics apply to the 75 Q Input,
Option 07 (75
Input)
Table 7-3: Option 07 Alternate Specifications
Characteristic
Performance Requirement
Supplemental Information
Input
75 Q.
Input Impedance
Return Loss 5 MHz to
800 MHz
17 dB (1.35:1 VSWR).
Return Loss 800 MHz
to 1000 MHz
13dB (1.6:1 VSWR) with >10dB
attenuation.
Maximum Input Level
With 0 dB Attenuation
+78 dBmV.
With 20 dB or More
Attenuation
+78 dBmV, 100 VDC maximum
(DC + Peak AC).
Frequency
Center Frequency Operating
Range
Static Resolution Bandwidth
0 to 1000 MHz.
Within 20% of 300 kHz bandwidth
(SdBdown)
300 kHz filter replaces the standard
1 00 kHz filter.
±2.0 dB about the midpoint between two extremes
Frequency response is measured
with > 10 dB RF Attenuation.
Frequency Response
5 MHz to 1000 MHz
The response figure includes the
effects of:
• Input VSWR
• Mixer
• Gain variations
Variations in display flatness contribute about 1 dB to the response
figure.
1 MHz to 5 MHz
495 & 495P User Manual
Typically <3 dB down from the
5 MHz response.
7-3
Options
Table 7-3: Option 07 Alternate Specifications (Cont.)
Characteristic
Performance Requirement
Supplemental Information
Amplitude
-68dBmVto +99 dBmV.
Reference Level Range (with 0
Reference Level Offset)
+89 dBmV is achievable in MIN
NOISE or REDUCED GAIN mode.
+99 dBmV is achievable with MIN
NOISE on and with REDUCED
GAIN mode activated.
Sensitivity
Measured at 25° C with:
• 0 dB RF Attenuation (Min
Atten 0 dB
Equivalent Input Noise
Sensitivity
5 MHz to 1000 MHz,
75 Q RF INPUT
10 Hz Filter
100 Hz Filter
1 kHz Filter
10 kHz Filter
300 kHz Filter
1 MHz Filter
3 MHz Filter
• Narrow Video Filter On
-82 dBmV
-76 dBmV
-66 dBmV
-56 dBmV
• Digital Storage On
• Max Hold Off
-41 dBmV
• Peak/Average in Average
-36 dBmV
• 1 s Time/Div
-31 dBmV
• Zero Span
• Input Terminated in Characteristic Impedance
50 Q RF INPUT
300 kHz Filter
• Vertical Display 2 dB/div
(5dB/divin 10 Hz Filter)
-90 dBmV
Output
Calibrator Output
CAL OUT Level
Impedance
+20 dBmV ±0.5 dB
100 MHz comb of markers provide
amplitude calibration at 100 MHz.
75 Q nominal.
Physical
Weight
7-4
Option 07 adds 7 ounces (0.2 kg)
to the standard instrument. Weight
with only Option 07 added is
43 Ibs. 4 oz. (19.7 kg) (including
cover and standard accessories,
except manuals).
Options
Options
Option 39 (Silver
Batteries)
Option 39 provides silver batteries for the instrument's battery-powered
memory. The battery life at +55° C is 1 -2 years, and 2-5 years at +25°
We recommend removing the silver batteries during long-term storage.
Option 42 (110 MHz
IF Output)
This option provides a 110 MHz IF output with bandwidth greater than
4.5 MHz for broad-band, swept receiver applications. Table 7-4 lists the
changes from the standard instrument.
c.
Table 7-4: Option 42 Alternate Specifications
Characteristic
Performance Requirement
Supplemental Information
Frequency
Center Frequency
108.5 MHz to 11 1.5 MHz
3 dB Bandwidth
>4.5MHz
Bandpass Ripple
<0.5dB
Symmetry About 1 10 MHz
±1.0 MHz
Power
Power Out with -30 dBm Input
and Signal at Full Screen
<OdB
Nominal output impedance is
50 O.
1 dB compression of output
>0 dBm in MIN DISTORTION and
non-reduced gain modes only.
Option 52 (North
American 220 V)
495 & 495P User Manual
Option 52 provides a North American 220 V configuration with the standard
power cord. The fuses are replaced with 2A slow blow.
7-5
Options
7-6
Options
The following glossary is presented as an aid to better understand the terms
as they are used in this document and with reference to spectrum analyzers.
General Terms
Center Frequency
That frequency which corresponds to the center of a frequency span,
expressed in hertz.
Baseline Clipper (Intensifier)
A means of increasing the brightness of the signal relative to the baseline portion of the display.
dBc
Decibels referenced to carrier level.
dBm
A unit to express power level in decibels referenced to 1 milliwatt.
dBmV
A unit to express voltage levels in decibels referenced to 1 millivolt.
dBuV
A unit to express voltage levels in decibels referenced to 1 microvolt.
Effective Frequency Range
That range of frequency over which the instrument performance is
specified. The lower and upper limits are expressed in hertz.
Envelope Display
The display produced on a spectrum analyzer when the resolution
bandwidth is greater than the spacing of the individual frequency components.
Frequency Band
A continuous range of frequencies extending between two limiting
frequencies, expressed in hertz.
Full Span (Maximum Span)
A mode of operation in which the spectrum analyzer scans an entire
frequency band.
Intermodulation Spurious Response
(Intermodulation Distortion — IMD)
An unwanted spectrum analyzer response resulting from the mixing of
the nth order frequencies, due to non-linear elements of the spectrum
analyzer. The resultant unwanted response are displayed.
495 & 495P User Manual
G-1
Glossary
Line Display
The display produced on a spectrum analyzer when the resolution
bandwidth is less than the spacing of the signal amplitudes of the individual frequency components.
Line Spectrum
A spectrum composed of signal amplitudes of the discrete frequency
components.
Markers
The instrument uses three types of markers:
Update Marker
Marks the current sweep position in a digital storage display as the
display is being updated.
Video Markers
Marker signals applied to the external VID | MARKER input from a
Tektronix 1405 Television Sideband Analyzer. The Video Markers
mark frequencies of interest on the television signal.
Waveform Markers
When the Marker function is enabled, it provides a movable cursor
with readout of frequency and amplitude at the marker position.
When the delta marker mode is enabled, a second marker allows
operations and readout between the two marker positions. (Also see
Waveform Marker Terms.)
Maximum Safe Input Power
WITHOUT DAMAGE
The maximum power applied at the input which will not cause
degradation of the instrument characteristics.
WITH DAMAGE
The minimum power applied at the input which will damage the
instrument.
Pulse Stretcher
A pulse shaper that produces an output pulse, whose duration is greater
than that of the input pulse, and whose amplitude is proportional to that
of the peak amplitude of the input pulse.
Scanning Velocity
Frequency span divided by sweep time and expressed in hertz per
second.
Signal Identifier
A means to identify the spectrum of the input signal when spurious
responses are possible.
Video
The term is used here generally to mean a signal after the detector
stage. It can also be used more specifically to mean a base-band (zero
carrier frequency) television signal.
G-2
Glossary
Glossary
Video Filter
A post detection low-pass filter.
Zero Span
An operating mode in which the frequency span is reduced to zero.
Frequency Terms
Display Frequency
The input frequency as indicated by the spectrum analyzer and expressed in hertz.
Frequency Drift
Gradual shift or change in displayed frequency over the specified time
due to internal changes in the spectrum analyzer, where other conditions remain constant. Expressed in hertz per second.
Frequency Linearity Error
The error of the relationship between the frequency of the input signal
and the frequency displayed (expressed as a ratio).
Frequency Span (Dispersion)
The magnitude of the frequency band displayed; expressed in hertz or
hertz per division.
Impulse Bandwidth
The displayed spectral level of an applied pulse divided by its spectral
voltage density level assumed to be flat within the pass-band.
Residual FM (Incidental FM)
Short term displayed frequency instability or jitter due to instability in the
spectrum analyzer local oscillators. Given in terms of peak-to-peak
frequency deviation and expressed in hertz or percent of the displayed
frequency.
Shape Factor (Skirt Selectivity)
The ratio of the frequency separation of the two (60 dB/6 dB) down
points on the response curve to the static resolution bandwidth.
Static (Amplifier) Resolution Bandwidth
The specified bandwidth of the spectrum analyzer's response to a CW
signal, if sweep time is kept substantially long. This bandwidth is the
frequency separation of two points on the response curve, usually 6 dB
down, if it is measured either by manual scan (true static method) or by
using a very low speed sweep (quasi-static method).
Zero Pip (Response)
An output indication which corresponds to zero input frequency.
495 & 495P User Manual
G-3
Glossary
Amplitude Terms
Deflection Coefficient
The ratio of the input signal magnitude to the resultant output indication.
The ratio may be expressed in terms of volts (rms) per division, decibels
per division, watts per division, or any other specified factor.
Display Dynamic Range
The maximum ratio of the levels of two non-harmonically related sinusoidal signals each of which can be simultaneously measured on the
screen to a specified accuracy.
Display Flatness
The unwanted variation of the displayed amplitude over a specified
frequency span, expressed in decibels.
WOTE
Display flatness is closely related to frequency response. The main
difference is that the spectrum display is not moved to center
screen.
Display Law
The mathematical law that defines the input-output function of the instrument. The following cases apply:
Linear
A display in which the scale divisions are a linear function of the
input signal voltage.
Square law (power)
A display in which the scale divisions are a linear function of the
input signal power.
Logarithmic
A display in which the scale divisions are a logarithmic function of
the input signal voltage.
Display Reference Level
A designated vertical position representing a specified input level. The
level may be expressed in dBm, volts, or any other units.
Dynamic Range
The maximum ratio of the levels of two signals simultaneously present at
the input which can be measured to a specified accuracy.
Frequency Response
The unwanted variation of the displayed amplitude over a specified
center frequency range, measured at the center frequency, expressed in
decibels.
G-4
Glossary
Glossary
Gain Compression
Effect seen at an input level where the analyzer circuits have less gain
than their small signal values. This is usually specified at the 1 dB compression point in terms of the input level required to reduce the gain by
1 dB.
Hum Sidebands
Undesired responses created within the spectrum analyzer, appearing
on the display, that are separated from the desired response by the
fundamental or harmonic of the power line frequency.
Input Impedance
The impedance at the desired input terminal. Usually expressed in terms
of VSWR, return loss, or other related terms for low impedance devices
and resistance-capacitance parameters for high impedance devices.
Noise Sidebands
Undesired response caused by noise internal to the spectrum analyzer
appearing on the display around a desired response.
Relative Display Flatness
The display flatness measured relative to the display amplitude at a fixed
frequency within the frequency span, expressed in decibels.
Residual Response
A spurious response in the absence of an input signal. (Noise and zero
pip are excluded.)
Sensitivity
Measure of a spectrum analyzer's ability to display minimum level signals, expressed in volts or decibels. Intermediate frequency (IF) bandwidth, display mode, and any other influencing factors must be given.
Spurious Response
A response of a spectrum analyzer wherein the displayed frequency is
not related to the input frequency.
Digital Storage Terms
Clear (Erase)
Presets memory to a prescribed state, usually that denoting zero.
Digitally Averaged Display
A display of the average value of digitized data computed by combining
serial samples.
Digitally Stored Display
A display method whereby the displayed function is held in a digital
memory. The display is generated by reading the data out of memory.
495 & 495P User Manual
G-5
Glossary
Max Hold (Peak Mode)
Digitally stored display mode which, at each frequency address,
compares the incoming signal level to the stored level and retains the
greater. In this mode, the display indicates the peak level at each frequency after several successive sweeps.
Multiple Display Memory
A digitally stored display having multiple memory sections which can be
displayed separately or simultaneously.
Save
A function which inhibits storage update, saving existing data in a section of a multiple memory (e.g., Save A).
Scan Address
A number representing each horizontal data position increment on a
directed beam type display. An address in a memory is associated with
each scan address.
View (Display)
Enables viewing of contents of the chosen memory section (e.g., "View
A" displays the contents of memory A; "View B" displays the contents of
memory B).
Volatile/Non-volatile Storage
A volatile storage system is one where any total loss of power to the
system will result in a loss of stored information. Non-volatile memory is
not subject to the instrument power supply for its storage.
Waveform Marker
Terms
Active Trace
Live Trace or the B-SAVE A trace (a trace recalled into B is not an active
trace).
Inactive Trace
SAVE A trace or a trace recalled into the B display before the sweep is
started.
Live Trace
Any combination of the A trace and/or the B trace when SAVE A is off.
Primary Marker
The marker displayed in the Single Marker mode whose frequency
and/or position is changed when tuning with the CENTER/MARKER
FREQUENCY control. When two markers are displayed, the brightest
marker is the Primary marker.
Secondary Marker
The "second" marker; displayed only in the Delta Marker mode.
G-6
Glossary
MANUAL CHANGE INFORMATION
At Tektronix, we continually strive to keep up with latest electronic developments
by adding circuit and component improvements to our instruments as soon as they
are developed and tested.
Sometimes, due to printing and shipping requirements, we can't get these
changes immediately into printed manuals. Hence, your manual may contain new
change information on following pages.
A single change may affect several sections. Since the change information sheets
are carried in the manual until all changes are permanently entered, some
duplication may occur. If no such change pages appear following this page, your
manual is correct as printed.