Tektronix 492 Service manual

Tektronix , Inc.
P.O.
Box 500
Beaverton ,
Oregon
97077
070-2729-00
Tektronix
COMMITTED TO
EXCELLENCE
Serial
Number
492
OPERATORS
HANDBOOK
First Printing MAR 1980

WARRANTY
Tektronix warrants that this product is free from defects in materials and workmanship . The
warranty period is one ( 1 ) year from the date of shipment . Tektronix will , at its option , repair or
replace the product if Tektronix determines it is defective within the warranty period and if it is
returned ,
freight prepaid ,
to a
service center
designated by
Tektronix .
Tektronix is not 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 from connecting the product to
incompatible equipment ;
c
. if
personnel other than
Tektronix
representatives
modify
the
hardware
or software .
There is no implied warranty of fitness for a particular purpose . Tektronix is not liable for
consequential
damages
.
Copyright © 1980 Tektronix , Inc. All rights reserved . Contents of this publication
may not be reproduced in any form without the written permission of Tektronix , Inc.
Products of Tektronix , Inc. and its subsidiaries are covered by U.S. and foreign
patents and / or pending patents .
TEKTRONIX
, TEK ,
SCOPE -
MOBILE , and
Tektronix ,
Inc.
Printed in U.S.A. Specification and price change privileges are reserved .
TEKTRONIK
are
registered
trademarks
of

Section 1
Section 2
DESCRIPTION AND
SPECIFICATION
TABLE OF CONTENTS
PRODUCT DESCRIPTION
Specification
Summary
OPERATION
PREPARATION FOR USE ..
Power Source and Power
Requirements ...
Controls , Connectors , and
Indicators
Initial Turn On .
Calibrate
Center
Frequency
Readout
Page
1-1
1-1
1-1
2-1
2-1
2-2
2-2
2-14
2-16
Calibrate Reference Level and
Dynamic Range .
2-16
Check Span Accuracy and Linearity 2-17
Section 3
492
Operator's
Handbook
GENERAL OPERATING
INFORMATION
Page
3-1
3-1
3-1
SIGNAL APPLICATION
RF
Input
Connector
Resolution
Bandwidth
,
Frequency
Span
, and
Sweep Time
Using the
PEAKING
Control
.
Using the
Signal
Identifier ...
Using
the Video
Filters
.
Time
Domain
Operation
Triggering the Display
Sweeping the Display
..
Manual
Scan
of
the
Spectrum
Reference Level , RF Attenuation ,
and
Vertical
Display
3-6
Delta A Mode . . . .
3-7
MIN NOISE / MIN DISTORTION .. 3-8
Digital
Storage ( Option 02 ) ..
3-8
3-2
3-3
3-3
3-4
3-4
3-4
3-6
3-6
i

OPERATORS
SAFETY
SUMMARY
The general safety information in this part of the summary
is for both operating and servicing personnel . Specific
warnings and cautions will be found throughout the
manual where
they apply ,
but may not
appear in this
summary
.
TERMS
In This Manual
CAUTION statements identify conditions or practices that
could result in damage to the equipment or other property .
WARNING statements identify conditions or practices
that could result in personal injury or loss of life .
As
Marked on
Equipment
CAUTION indicates a personal injury hazard not im
mediately accessible as one reads the marking , or a
hazard to property including the equipment itself .
ii
DANGER indicates a personal injury hazard immediately
accessible
as
one reads the
marking
.
In This Manual
SYMBOLS
This symbol indicates where applicable
cautionary
or
other
information
is to
be
found .
As
Marked on
Equipment
A
492
Operator's
Handbook
DANGER
-
High voltage .
Protective
ground ( earth )
terminal .
ATTENTION - refer to manual .
Power Source
This product is intended to operate from a power source
that will not apply more than 250 volts rms between the
supply conductors or between either supply conductor
and ground . A protective ground connection by way of the
grounding conductor in the power cord is essential for
safe
operation .

Grounding the
Product
This
product
is
grounded
through
the
grounding conduc
tor of the
power
cord .
To avoid
electrical
shock
, plug the
power cord into a properly wired receptacle before
connecting to the product input or output terminals . A
protective ground
connection by way of the
grounding
conductor
in
the power
cord is
essential for safe opera
tion .
Danger
Arising
From
Loss of
Ground
Upon loss of the protective - ground connection , all
accessible conductive parts ( including knobs and con
trols that may appear to be insulating ) can render an
electric
shock
.
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 .
For detailed information on power cords and connectors ,
see
492 Service
Vol . 1 .
Refer cord and connector changes to qualified service
personnel .
Use the Proper Fuse
To avoid fire hazard , use only the fuse of correct type ,
voltage rating and current rating as specified in the parts
list for
your
product
.
Refer fuse replacement to qualified service personnel .
Do Not Operate in Explosive Atmospheres
To avoid explosion , do not operate this product in an
explosive atmosphere unless it has been specifically
certified for
such
operation .
Do Not Remove Covers or Panels
To avoid personal injury , do not remove the product
covers or panels . Do not operate the product without the
covers
and panels
properly installed .
492
Operator's
Handbook
iii

iv
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FREQUENCY
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FREQUENCY
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492
Spectrum
Analyzer .
492
ANALYZE
492 Operator's Handbook
*
1 ?
2729-1

SECTION
1
DESCRIPTION
AND
SPECIFICATION
PRODUCT
DESCRIPTION
The
492
Spectrum
Analyzer is a
high
performance ,
compact
, portable
spectrum
analyzer
that displays ab
solute
amplitude and
frequency
information
of
signals .
within
the
frequency spectrum
of 50 kHz to 21
GHz with
the
internal
coaxial mixer
, and up to
60 GHz with
optional
external
TEKTRONIX High
Performance
Waveguide Mix
ers . The 8.4 X 10.2 cm crt face reads out all major display
parameters
.
SPECIFICATION
SUMMARY
Complete
instrument
specifications
can be
found in the
492
Operator's
Manual .
These
specifications
apply
at
ambient
temperature
of
25 ° C after a 2 hour warm - up period .
492
Operator's
Handbook
1-1

Frequency Related Specifications
Center frequency range , RF INPUT
Center
frequency
readout
accuracy
Frequency
drift
Amplitude Related Specifications
Frequency response and sensitivity :
Frequency Range
100 kHz - 4.1 GHz
without option 01
1-2
100 kHz - 1.8
GHz
with
option
01
1.7-5.5 GHz
3.0 7.1 GHz
5.4-18.0 GHa
15.0-21.0 GHz
a
ª
derate 1 dB
for
option 01 .
badd
-10
dB
for
option 01 .
100 kHz - 18 GHz ( usable to 21 GHz )
Within ( 5 MHz + 20 % of span / div ) or within ( 0.2 % of the
center frequency + 20 % of the span / div ) , whichever is greater .
< = 200 kHz / hour
Frequency Response
within 1.5 dB
within 1.5 dB
within 1.5
dBª
within
1.5 dBª
within
2.5 dBª
within 3.5 dBª
492
Operator's
Handbook
Sensitivity 1
kHz
Bandwidth
-115 dBm
-110 dBm
-115
dBm
-115
dBmb
-100
dBmb
-95
dBmb

Signal
Level
Accuracy
:
Signal levels are measured after the instrument is calibrated to the 100 MHz calibrator signal . Sources of error in
signal level measurement are shown below and are worst case for 25 ° Celsius operation . The sources of errors that are
actually encountered will depend upon signal frequency , level , and measurement technique .
Calibrator
RF Attenuator
Flatness
Band
switching
Resolution
bandwidth
switching
IF
gain
Display
and
log
within 0.3 dB maximum
within 1.4 dB
maximum
typically
1
dB
greater than the
frequency
response
within 1 dB with internal mixer
within 0.5 dB maximum
within 2.0 dB
maximum
within 2.0 dB maximum
Spurious Response Specification
Residual
(
signals
present
with no
RF input )
Harmonics of
input
signal
Harmonic of
input
signal
with
option
01
,
1.7-18 GHz
-100 dBm referred to mixer input for fundamental mixing
60 dB
down
for
-30
dBm signal
100 dB down for full screen signal ( MIN DISTORTION mode )
492
Operator's
Handbook
1-3

Third order intermodulation distortion ,
10 kHz - 18 GHz
Third order intermodulation distortion with
option
01 ,
1.7-18
GHz
RF INPUT
Specifications
Maximum input level
Input
VSWR
1 dB compression point
without
option 01
with option 01 , 50 kHz - 1.7 GHz
with option 01 , 1.7-2.0 GHz
with option 01 , 1.8-18 GHz
L.O. emmission
without
option
01
with option 01
1-4
at least 70 dB down from any two on screen signals
within any frequency span -30 dBm inputs
100 dB down for two inputs of 100 MHz minimum
separation
+30 dBm ( > = 20 dB RF attenuation )
+13 dBm ( no RF attenuation )
better than 1.45 : 1 with > = 10 dB RF attenuation
-10 dBm
( no RF
attenuation )
-10 dBm ( no RF attenuation )
-28 dBm
( no RF
attenuation )
-10 dBm ( no
RF
attenuation )
-10 dBm ( no RF attenuation )
-70 dBm ( no
RF
attenuation )
492
Operator's
Handbook

Sweep and
Display
Specifications
Sweep
time
accuracy
Trigger sensitivity
Trigger
bandwidth
VERT
OUTPUT
Levels
bottom of
screen
top
of screen
HORIZ OUTPUT levels
left
side
of
screen
right
side
of
screen
PEN LIFT
External
horizontal
input
left
side
of
screen
right side
of
screen
within
5 %
> = 2.0 division of signal for internal , and 0.5 V peak minimum to
50 V peak maximum external
15 Hz to 1 MHz
volt
nominal
+4 volt
nominal
-2.5 volt nominal
+2.5 volt nominal
TTL
compatible .
Goes
high to
lift pen .
volt
nominal
+10 volt nominal
492
Operator's
Handbook
1-5

Other Specifications
Instrument
power
Leakage
current
Storage temperature
Operating
temperature
Storage
altitude
Operating
altitude
Weight
1-6
90-132 VAC
or
180-250 VAC
internally
selectable
210 Watts maximum ( options 01 , 02 , 03 )
5
mA peak
( options 01
, 02 , 03 )
-62 ° C
to + 75 °
C
-15
° C to
+ 55 ° C
12,192
meters (
40,000 feet )
maximum
4,752
meters
( 15,000
feet
)
maximum
21.78 kg ( 44 lb )
492
Operator's
Handbook
8

SECTION 2
OPERATION
PREPARATION
FOR
USE
The 492
can be
installed
in any
position
that allows
air
flow in
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 . A
fan
draws
air
in
through
the bottom
and expels
air
out the back
.
Avoid
locating the
492
where
paper ,
plastic , or like
material
might
block
the air
intake .
The
front panel
cover for the 492
provides
a dust
- tight
seal .
Use the
cover to
protect
the
front
panel
when
storing
or
transporting
the
instrument .
The
cover
is
also
used
to
store
accessories and
external
waveguide
mixers
.
The
cover is
removed
by first
pulling up and
in on
the two
release
latches
then pulling
up on
the
cover .
The door to
the
accessories
compartment
is
unlatched by
pressing the
latch
to the side
and lifting
the cover .
The
handle of the
492 can
be
positioned at
several
angles
to
serve as a tilt
stand , or it
can
be
positioned at
the
top
rear of
the
instrument
between
the
feet
and
the rear
panel so
492
instruments can
be
stacked
. To
position the
handle
, press
in at
both
pivot
points
and rotate
the handle
to the
desired position .
CAUTION
Removing
or
replacing
the
cabinet
on
the
instrument
can be
hazardous .
The
cabinet
should
only
be
removed by
qualified
service
personnel .
492
Operator's
Handbook
2-1

POWER
SOURCE
AND
POWER
REQUIREMENTS
The
492
is
designed to
operate
from a
single
-
phase
power
source
that
has one of
its
current
-
carrying
conduc
tors (
neutral
) at
ground
(
earth
)
potential
.
Operating
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
volt
single
-
phase
,
three
- wire
system ) is
not
recommended
,
since
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
,
the
unit
frame
must be
connected to an
earth
ground .
Power
and
voltage
requirements
are printed on
a
back
panel
plate mounted
below the
power input jack .
The 492
can be
operated
from
either
a 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 . A
multipin (
harmonica
)
type
connector
on
2-2
the
power
supply
etched
circuit board can be
positioned
to
accommodate
either
voltage
range
.
When
the
power
supply
circuitry
is
changed
to
accommodate a
different
power
source
, the
information
plate
on the
back
panel
must
also
be
changed to
reflect
the
new
power re
quirements .
Refer
power
input
changes
to
qualified
service
personnel .
Instructions are
contained in
the
Service
Information
section
.
WARNING
Only
qualified
service
personnel
should
attempt
to
change the
power
input requirements .
Unfamiliarity
with
safety
procedures
can
result in
personal
injury
.
Refer
to
the
Safety
Summary at
the
front of this
manual
.
CONTROLS
,
INDICATORS
,
AND
CONNECTORS
The
following
describes the
function of
the
controls ,
indicators
,
and
connectors on
the front
and
rear
panels of
the 492.
Figures 2-1 and 2-2
illustrate their
locations
. All
options
are
covered in this
description and
some
functions
are
described
in
greater
depth
under
Operating Informa
tion
.
492 Operator's Handbook
(
8
)

Front
Panel
(
Fig
.
2-1
)
1
2
3
4
5
INTENSITY . Controls brightness of the crt trace
and crt
readout
. ( Focus is
automatically
adjusted
electronically . )
READOUT . Switches crt readout on or off . All
spectrum
analyzer
parameters
are read
out
except Time / Div . Brightness is proportional to
the trace brightness and the ratio can be
readjusted by service personnel .
GRAT
ILLUM .
Switches
graticule light on or off .
BASELINE CLIP . When activated , the baseline of
the
display
is
clipped
or
subdued to
increase the
contrast between the display and the baseline .
TRIGGERING . One of four triggering modes can
be
selected by
pushbuttons that
illuminate
when
activated . A SINGLE SWEEP pushbutton plus a
READY indicator provide single sweep operation .
FREE RUN - When activated , the sweep is free
running
without
regard to trigger
signals . When
selected , all
other triggering
modes are
canceled .
6
INT -
When activated , the
sweep
is
triggered by
any
signal at the
left edge of
the
display with an
amplitude of 1.0 division or more . Other trigger
modes are canceled .
LINE - When
activated
, a
sample
of
the ac power
line voltage is used to trigger the sweep . All other
modes are
canceled
when selected .
EXT - When selected , the sweep is triggered by
signals between 0.5 volt peak ( minimum ) to
50 volts peak ( maximum ) that are applied
through the
back panel EXT
IN
HORIZ /
TRIG
connector . When
EXT is
selected , the other
modes are canceled .
SINGLE
SWEEP
. When
selected
, one
sweep is
initiated after the sweep circuit has been
triggered
.
Pushing
this button
does not
cancel
the trigger modes . The button must be pressed to
rearm the sweep circuit after the sweep has run .
When
single sweep
mode
is first
selected , the
present
sweep is
aborted and the
sweep circuit is
not armed . To cancel single sweep , press one of
the trigger mode pushbuttons .
492
Operator's
Handbook
2-3

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7
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READY . When
SINGLE SWEEP is
selected
,
this
indicator lights while the sweep circuit is armed
and ready for a trigger signal . The indicator stays
lit
until
the
sweep
ends
.
MANUAL
SCAN
. When the
TIME / DIV
selector is
in the MNL position , this control will manually
scan
the
spectrum
.
TIME / DIV . Selects sweep rates from 5 s / div to
20 μs / div in 5-2-1 sequence . This switch also
selects AUTO , EXT , and MNL modes .
AUTO (
automatic
) -In this
position
the
sweep
rate is selected by the microcomputer to maintain
a calibrated display for any FREQ SPAN / DIV ,
RESOLUTION , and VIDEO FILTER combination .
EXT
( external
input ) -This
position
connects the
rear
panel EXT
IN HORIZ / TRIG
connector
to the
horizontal sweep circuit . A voltage ramp of to
+10 volts will sweep 10 divisions of the horizontal
(
x )
axis .
MNL ( manual ) -In this position the horizontal
axis can be swept with the MANUAL SCAN
control .
10
11
12
13
FREQUENCY .
Tunes the
center
frequency
.
Tune
rate is proportional to the selected FREQ
SPAN / DIV . Any given signal moves across the
display at a constant rate for all spans . In MAX
span
, the tuning
range
depends on the band
; for
example
,
in
Band
2 (
1.7-5.5 GHz ) the
frequency
dot will not tune to the extreme left edge of the
graticule , or in Band 6 ( 15-21 GHz ) the dot will
tune only to the right of center .
FREQUENCY RANGE ( band ) . These two push
buttons
shift
the
center
frequency
range up or
down . Frequency range of the band is displayed
on the crt readout .
AF . A
convenience for
measuring
frequency
difference
between
signals
( see
Operational
Procedure ) . When selected , the frequency
readout
goes
to
zero
. It
will
then
read out the
deviation from this
reference as the
FREQUENCY
is tuned .
CAL . When
activated
, the
frequency
readout
can
be
calibrated to center
frequency
by
adjusting
the
FREQUENCY control for the
correct reading .
When calibrated , deactivate the CAL mode .
492
Operator's
Handbook
2-5

14
15
2-6
DEGAUSS . When the DEGAUSS button is
pressed , current through the tuning coils of the
YIG oscillator ( 1st LO ) and YIG preselector
( when installed ) is reduced to zero to minimize
hysteresis effects . This enhances center
frequency and display amplitude accuracy .
DEGAUSS does not function when the FREQ
SPAN / DIV
is less than
1 MHz / Div
.
Degauss the
tuning coils after a significant frequency change
and before calibrating the center frequency
readout .
IDENTIFY 500 kHz ONLY . Signal identify feature
is
functional
only when
the FREQ
SPAN / DIV is
500 kHz . When activated ( button lit ) true signals
will change amplitude each sweep ; images and
spurious response signals will shift horizontally
or off screen . To ensure that the signal is
changing
amplitude every
sweep
,
decrease the
sweep rate so each sweep can be analyzed ; or , if
the instrument has digital storage , activate SAVE
A
,
VIEW B.
When the true signal is centered under the dot
marker after degauss , the FREQUENCY readout
is the signal frequency ( within specification ) .
Degauss
by
pressing
DEGAUSS
at
FREQ
SPAN / DIV setting of 1 MHz or 2 MHz .
16
PHASE LOCK
( Option 3 ) . The
1st LO is locked
to
a stable internal reference and the 2nd LO swept
to reduce residual FM in narrow spans ; the button
lights when phase lock is active . In narrow spans
phase lock
can be
turned off
or back
on by
pressing
the
button .
Spans for
which the
microcomputer
automatically
selects
phase
lock
are
:
Band
1
, 2 ,
3
4
5 and above
492
Operator's
Handbook
Span
/
Div
50
kHz and
below
100
kHz and
below
200
kHz and
below
17
AUTO RESOLUTION . This is a pushbutton that
activates automatic bandwidth selection for the
selected FREQ SPAN / DIV and TIME / DIV and
VIDEO FILTER . An internal microcomputer
selects bandwidth to maintain a calibrated
display . When the TIME / DIV is in AUTO mode ,
resolution bandwidth becomes a function of the
FREQ SPAN / DIV selection .
@

( @
)
18
FREQUENCY SPAN / DIV . This is a continuous
detented control that selects frequency span / div .
Span / div is indicated by the crt readout . Range of
the span / div selection depends on the frequency
band and options . Table 3-1 lists the range for the
various
bands and
options .
Selection is a
5-10-20
sequence
plus MAX
span
and Hz
span
positions
.
Band
1-3 ( 0-7.1 GHz )
4-5 ( 5.4-21 GHz )
6 ( 18-26 GHz )
7-8 ( 26-60 GHz )
9 ( 60-90 GHz )
10 ( 90-140 GHz )
11 ( 140-220 GHz )
Table 2-1
SPAN / DIV
RANGES
VERSUS
BAND
AND
OPTION
Narrow
Span /
Div
Standard
When MAX span is selected , the span displays the
full
band .
Sweep
beyond the band is
clamped to
the baseline . A dot marker near the top of the
screen indicates the position on the span of the
crt
frequency
readout
. This dot
and
frequency
point
will be
center
screen
when the
FREQ
SPAN / DIV is reduced below MAX span position .
When
zero
span is
selected Time /
Div is read out
instead
of
Span / Div .
5 kHz
10
kHz
20
kHz
50 kHz
100 kHz
100 kHz
100 kHz
Option
3
500
Hz
500 Hz
500
Hz
500
Hz
500
Hz
500
Hz
500
Hz
492
Operator's
Handbook
Wide
Span /
Div
All Instruments
200
MHz
500 MHz
1
GHz
2
GHz
2
GHz
5 GHz
10 GHz
2-7

19
RESOLUTION
BANDWIDTH . This is
also a
continuous detented
control that selects
resolution
bandwidth .
Bandwidth is
indicated
by
crt readout . Range of selection is 1 kHz to 1 MHz
in decade steps . An additional resolution band
width of 100 Hz , when Option 3 is installed , is
provided . Changing the resolution bandwidth
with this
control deactivates AUTO
RESOLUTION .
20
2-8
VERTICAL
DISPLAY .
These
four
pushbuttons
select the
display
mode . The
crt
readout
indicates
scale
factor
.
10
dB
/
DIV
-
When
activated ,
the
dynamic
range
of the
display
is a
calibrated 80 dB with
each
major graticule representing 10 dB .
dB /
DIV -
Increases
resolution so
that
each
major
graticule
division
represents
2 dB .
LIN -
Selects
a
linear
display
between
zero
volts
( bottom graticule line ) and the reference level
( top graticule line ) scaled in volts / division . See
REFERENCE
LEVEL .
21
22
PULSE STRETCHER - Increases the fall time of
pulse signals so very narrow pulses in a line
spectrum display can be seen . The effect is most
apparent for
discrete
signals
analyzed
at
resolution
bandwidths that
are
narrow
compared
to the span ; PULSE STRETCHER may be
necessary for digital storage of such signals ,
especially if they are averaged .
VIDEO FILTER
. One of two
(
NARROW and
WIDE ) filters can be activated to reduce the video
bandwidth and
reduce
and
reduce
high
frequency
components for display noise averaging . The
NARROW
filter is
approximately 1 /
300th
of
the
selected resolution bandwidth ; the WIDE filter is
about
1 /
30th the
bandwidth .
Activating
either
filter cancels or deactivates the other filter . Press
the pushbutton to switch the filters off .
DIGITAL
STORAGE
( Option 2 ) .
Five
pushbuttons and one
control operate the
digital
storage functions . With none of the pushbuttons
activated
, the
492
display is not
stored .
VIEW A ,
VIEW B - When
either or
both of these
pushbuttons are selected , the pushbutton
illuminates and the
contents
of
memory
A
and / or
492 Operator's Handbook