Tektronix TR 503 User manual

T~ktronoc
Tektronix, Inc .
P .O . Box 500
Beaverton, Oregon

97077

Serial Number
COMMITTED TO EXCELLENCE
INSTRUCTION
MANUAL
070-3526- 0 0

First Printing Aug 1980

Section 1 GENERAL
INFORMATION AND
SPECIFICATIONS
Section 2 OPERATING INSTRUCTIONS
TABLE OF
CONTENTS
Introduction .................
1-1
Overview .......... : ........
1-1
Standards .................. 1-2
Electrical Characteristics ..........

1-2
Environmental
Characteristics ...... 1-3
Physical Characteristics
.......... 1-3
Accessories ................. 1-3
Introduction
................... 2-1
About the Tracking Generator ...... 2-1
Installation . ...................
2-1
Repackaging
.................. 2-1
Functions of the Controls and
Connectors ...................
2-1
Operators Checkout
Procedure ..... 2-2
Check Flatness .............. 2-3
Check Output Level ...........
2-4
Tracking Adjustment .......... 2-4
Measuring Frequency .......... 2-4
WARNING
THE FOLLOWING SERVICING
INSTRUCTIONS
AREFOR USE BY QUALI
FI ED PERSONNEL ONLY .
T O AVOID
PERSONAL INJURY, DO NOT
PER-
FORMANYSERVICING OTHER THAN
THAT CON-
TAINED IN OPERATING
INSTRUCTIONSUNLESS
YOUARE QUALIFIED TO DOSO
.
Section 3
THEORY OF OPERATION
General Description . ............
3-1
Block Diagram Description
........ 3-3
Detailed
Circuit Description ....... 3-3
RF and Microwave Circuits ......

3-3
TR 503
LIST OF
ILLUSTRATIONS

.................

iii

Section 3

THEORYOF
OPERATION (cont)
OPERATORS
SAFETY SUMMARY ...........

iv
SERVICING SAFETY SUMMARY ............

v
Section 4 CALIBRATION
Section 5
MAINTENANCE
Bias and Leveling Loop Circuitry
. .
3-3
Phase Lock Loop . ....... . . . . .
3-4
Power Supply
Regulators ...... . 3-5
Introduction .............. . . . . .
4-1
History
Information ......... .... 4-1
Equipment Required ........... . .
4-1
PERFORMANCE
CHECK ......... 4-2
Introduction
................... 4-2
Preliminary Inspection ........... 4-2
Performance Verification
.......... 4-2
Check
Frequency Range ........ 4-2
Check Output Level ...........
4-2
Check Flatness ..............
4-2
Check
Auxiliary Output Level .... 4-3
Check for Spurious Signals ......
4-3
ADJUSTMENTPROCEDURE ......
4-4
Introduction
................... 4-4
Complete or Partial Calibration ..... 4-4
Test Points ...................
4-4
Preliminary Preparation

..........

4-4
55
MHz Oscillator Mode Adjust ... 4-4
Adjust the Normalizing Attenuator .

4-5
Output Level Calibration ........
4-6
Introduction ................. 5-1
Static-Sensitive
Components ..... 5-1
Preventive Maintenance .......... 5-1
Cleaning . . . .... . ........... 5-2
Exterior . . . . . . ............
5-2
Interior . . .... . ........... 5-2
Lubrication . . . . . . . .......... 5-2
Visual Inspection . . . .......... 5-2
Transistor and Integrated
Circuit
Checks . ... . . . ........ .....
5-2
Performance Checks and
Recalibration . ..... . . . . . . .... 5-2
Troubleshooting ....... ... . . . ... 5-2

TR 503
TABLE OF
CONTENTS (cont)
Page

Page
Section 5
MAINTENANCE (cont)

Section 5 MAINTENANCE
(cont)
Troubleshooting Aids .......... 5-2

Replacing Assemblies .......... . . 5-7
Diagrams . . . ... ...........
5-2

~

Removing or
Replacing Semi-rigid
Circuit
Board Illustrations ..... 5-3

Coaxial Cables ............. . . 5-7
Wiring Color Code .......... 5-3

Replacement of Microwave
Multiple
Terminal (Harmonica)

Assemblies . . . . ..... . . . . ....

5-7
Connectors . ... ...........

5-3

Separating the TR 503 . . . ....

5-7
Resistor Values . . ..........

5-3

Removing the
Assembly . . . ...

5-7
Capacitor Marking ..........

5-3

Replacing the 2 .182 GHz Four Cavity
Diode
Color Code . ......... 5-4

Filter/Mixer Assembly . . ........ 5-8
Transistor and Integrated Circuit

Remove and Replace
the Filter
Pin Configuration .... . . .....

5-4

Assembly ........ .........

5-8
Diode Checks ........ .....

5-4

Filter AlignmentProcedure .... 5-8
General Troubleshooting
Technique 5-5
Corrective Maintenance ...... .... 5-6

Section 6 REPLACEABLE ELECTRICAL PARTS
Obtaining Replacement Parts .... 5-6
Parts Repair and
Replacement

Section 7 DIAGRAMS AND
CIRCUIT BOARD
Program ................ ... 5-6

ILLUSTRATIONS
Soldering Technique ..... ..... 5-6
Replacing
the Square Pin for the

Section 8 REPLACEABLE MECHANICAL PARTS
Multi-pin Connectors ....... ... 5-6
Selected Components ...... .... 5-6

CHANGE INFORMATION

LIST OF
I LLUSTRATI
ONS
r~ g .
No .

Page
2-1

`Plug-in module
installation ..........

2-2
2-2

TR 503/492 System with frequency counter 2-3
3-1

TR 503/492 System diagram .........
3-2
4-1

Setup for performance
check

........

4-3
4-2

Setup for adjustment procedure .......

4-5
4-3

Location of receptacle K, W520,
and C524 4-5
4-4

Location of adjustment
R215 and
adjustmentsR225, R220, and R222 . ...~ 4-6
5-1

Multipin (harmonica) connector
configuration
. ............ ....... 5-3
5-2

Color code for tantalum capacitors

....

5-3
5-3

Diode polarity markings ....... .....
5-4
5-4

Pin configuration
for semiconductor
components ... . . ............ . . . .
5-5
5-5

Procedure for separating two sections of
the TR 503 ...... ........... . . . . .

5-7
5-6

Typical position for the mixer in the
2 .182 GHz filter assembly .......... .

5-8
5-7

TR 503/492 System diagram
showing
phase-lock assembly
. ............. 5-9
5-8

Positioning the TR 503 to adjust the
2 .182 GHz filter/mixer assembly .......

5-10
5-9

Location of
P446on
the
mother board . .

5-11
5-10

Typical responses of the filter/mixer
assemblies . ............. ........
5-11

TR
503
._
The general
safety
information in this part of the
summary

supply conductors or
between
either supply conductor
is for
both operating
and servicing
personnel . Specific

and ground
. A protective
ground connection by
way ofthe
warnings
and
cautions will be
found throughout
the

grounding conductor in
the power cord is
essential for
manual where
they apply,
but may not appear
in this

safe operation .
summary
.
Terms In
This Manual
This mainframe
is grounded
through the grounding
CAUTION
statements
identify conditions
orpracticesthat

conductor
of the power cord . To
avoid electrical
shock,
could result in
damagetothe
equipment or other property
.

plug
the power cord into
a properly wired
receptacle
before connecting
to the product
input or output ter
WARNING statements
identify conditions
or practices

urinals . A
protective ground
connection by way of
the
that
could result
in personal injury or loss
of life .

groundingconductor
in
the power cord is essential
for
safe operation .
Terms
As Marked on
Equipment
CAUTION indicates
a personal injury
hazard not im-

panger
Arising From Loss of
Ground
mediately
accessible as
one reads the marking,
or a
hazard to property including
the
equipment itself .

Upon
loss of the protective-ground connection,

all
accessible
conductive parts (including
knobs and con
DANGER indicates a
personal injury
hazard immediately

trots
that may appear to be
insulating) can render an
accessible as
one reads the
marking .

electric shock .
Symbols In
This Manual

Do
Not Operate
in Explosive
Atmospheres
This
symbol indicates
where applicable
I

cautionary or
other information
is to be
found .
Symbols As
Marked on Equipment
Power
Source
iv
OPERATORS
SAFETY SUMMARY
DANGER
- High voltage
.
Protective
ground (earth)
terminal .
ATTENTION - refer to
manual .
Grounding
the Product
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 .
Do Not
Operate Without
Covers (for TM 500
plug-
ins
only)
To avoid personal
injury, do not
operate this product
The
mainframeisintendedtooperatefrom
apowersource

without covers
or panels
installed . Do not apply
power to
that does not apply more
than 250 volts rms
between the

the plug-in
via a plug-in extender
.
'J
'J
~r -

Do Not Service Alone
SERVICING
SAFETY
SUMMARY
FOR Q UALI
FI ED SERVICE PERSONNEL
ONL Y
Refer also to the preceding Operators Safely Summary .
Do
not perform internal service or adjustment of this
product unless another person capable of rendering first
aid and resuscitation is present .

Power Source
TR 503
Disconnect power before removing protective panels,
soldering, or replacing components .
The mai nframe is intended to operate from a power source
Use Care When Servicing With Power On

that does not apply more than 250 volts rms between the
supply conductors or between either supply conductor
Dangerous voltages exist at several poi nts in this product .

and ground .
A
protective ground connection by way of the
To avoid personal injury, do not touch exposed connec-

grounding conductor in the power cord is essential for
tions and components while power is on .

safe operation .

T R 503 Tracking Generator
3526-1

C
4
n
c
G
Overview
GENERAL
INFORMATION
AND
SPECI FI CATI ONS
The Operators part of the manual
is intended to helpthe
user obtain
maximum performance from the TR 503/492
system .
This part covers General Information and
the
Operating Instructions .
The Service part of
the manual covers the Theory of
Operation,
the Calibration section, and other service
information, including the block and schematic diagrams
of the TR 503 .
Section 1-TR 503
Introduction

Section 2-Operating Instructions ; introducesthe user
The TR 503
may be used to measure the
frequency

to the
TR 503/492 system and demonstrates a series of
response of
a device or component over a
100 kHz to

measurement procedures .
1 .8 GHz range . It is used
in conjunction with a TM 500
mainframe and a 492
Spectrum Analyzer . The tracking

Service
generator/spectrum
analyzer method of response
measurement
has intrinsically greater
rejection of device

Section 3-Theory of Operation ; describes
all major
or
environmental
noisethanthealternatesweptsine-wave

circuits of the TR 503 .
method .
Section 4-Calibration,
Part 1 : Performance Check ;
The greater noise
rejection is gained by having the
492

this subsection is used to verify all of the Performance
Spectrum
Analyzer track the TR 503 output
. Noise rejec-

Requirements in the Specification, and to determine the
tion is
improved as the Resolution
Bandwidth
of
the 492is

need for recalibration (adjustment) of the TR 503
.
decreased ; this is due to the 492 being
immune
to
noise
outside of the VR (Variable
Resolution IF) bandwidth .
Section 4-Calibration, Part 2 : Adjustment Procedure ;
_

this subsection is used to return the
TR
503 to
confor-
The TR 503 uses the 1st and2nd LO (local
oscillator)

mance

with

the

Performance

Requirements .

The
 :

outputs of the492 to generate a frequency
that tracks the

procedure is arranged
in functional blocks to facilitate
input of the 492 . The TRACKING
ADJUST control of the

referencing

from

the

Performance

Check

and

the
TR 503 allows fine
adjustment of this frequency .

Maintenance Instructions .
Points on the 492 display may
have their frequencies

Section

5-Maintenance

Instructions ;

describes
measured by adding a
frequency counter, such as the

routine and corrective maintenance procedures with
DC 508, to
the TR 503/492 system . Measurements may be

detailed

instructions for

replacing

assemblies,

sub-
made
directly from an external rf spectrum or
obtained

assemblies, and individual components .
An exploded
from the response curve of a device
under test .

drawing is part of Section 8 .
Section
6-Replaceable Electrical Parts ; provides in-
formation necessary to order replaceable parts and
assemblies related to the electrical functions of
the
instrument .
Section 7-Diagrams ; provides functional
block
diagram and circuit schematics . Pictorial layout
drawings
which show
subassembly and component locations are
adjacent to the diagram (usually on the back of the
preceding diagram) . Voltage and signal levels are
includ-
ed to aid in troubleshooting
.
The eight sections of the manual are :

Section 8-Replaceable Mechanical Parts ; provides
Operators

information necessary in order to replace
mechanical
parts . This list is cross-referenced
to the replaceable
Section
1-General Information and Specifications ;

electrical parts list where
appropriate . The Exploded
contains the instrument description, a list of accessories,

Drawing shows
the
assemblysequence
and identifies the
and a listing of the TR 503 Characteristics and
Perfor-

assemblies
. The Accessories page lists the standard and
mance Requirements .

optional accessories .

General Information
and
Specifications-TR 503
Changes
and Corrections
; provides updating informa-

Standards
lion for the
manual in the form
of inserts .
These inserts are
incorporated
into the
manual text and
diagrams when
the

The
abbreviations and
graphic symbols used
inthetext
manual
is updated .

and
diagrams of this manual
are based onANSIY1
.1-1972,
ANSI Y32 .2-1970,
and ANSI Y32
.14-1973 (American
National
Standards Institute, 345
East 47 Street, New
York,
N . Y . 10017)
.
The following
specificationsapplytotheTR
503 Track-

Items listed
in the Performance
Requirements
column
ing Generator
and the
TR 503/492 Spectrum
Analyzer

are verified
by completing
the
Performance Check
in
system .
Allow at least
30 minutes warmup
unless
noted

Section 4
of this manual
. Items listed
in theSupplemental
otherwise .

Information column
may not
be verified in this
manual ;
they are
either explanatory
notes or
performance
characteristics
for which no
limits are
specified .
Frequency
Range
Output
Level
Maximum Output
Adjustment
Steps
Attenuator Error
Output Impedance
Flatness
TR 503
Characteristic
TR 503/492 System
Dynamic
Range
TR 503/492 System
Residual FM (peak-to-peak)
TR 503
TR 503/492
System
SPECIFICATIONS
Table 1-1
ELECTRICAL
CHARACTERISTICS
Performance
Requirement
The TR 503 tracks
the 492 tuned
input frequency
from 100
kHz
to 1 .8
GHz .
OdBm±0 .5dB
.
0 to 9 dB
in 1 dB steps . 0
to 50
dB in 10 dB steps .
±0 .2 dB for each
1 dB change .
Total error
over the 59 dB
range
is ±2 dB .
±0 .75 dB from
100 kHz to
1 .8 GHz,
referred to 100
MHz .
±2 .25 dB from 100
kHz to
1 .8 GHz,
referred to 100 MHz .
Supplemental
I of ormation
An
additional 2 dB attenuation
is
provided by the front
panel VAR dB
control .
50 O nominal,
VSWR is 2 :1 or less
to 1 .8
GHz .
Typically ±2dB
or better .
>110 d8
<1 Hz
,10 Hz or
same as 492,
whichever
is
greater .

Auxiliary Output Level
Spurious
Signals
(100 kHz-1 .8 GHz)
Harmonic
Characteristic
Non-Harmonic

I -40 dB or
better with respect
to
the fundamental .
Temperature
Range
Operating
Non-Operating
Altitude Range
Operating
Non-Operating
Finish
Net Weight
Characteristic
Overall Dimensions
Table 1-1 (cont)
Pertormance
Requirement
0 .1 V rms minimum, into
a 50 O
I oad .
-20 dB or
better with respect
to
the fundamental .
ENVIRONMENTAL
CHARACTERISTICS
Characteristic
Table 1-2
Table 1-3
PHYSICAL CHARACTERISTICS
Anodized aluminum panel and chassis .
Front panel faced
with matt plastic .
8 Ibs (3
.64 kg)
General
Information and Specifications-TR
503
0 to +50° C .
Description
-40
to +75° C .
To 15,000 feet .
To 50,000
feet .
Descri pti on
Supplemental I of ormati on
5 .28in(134 .1mm)HX12in .(304 .8mm)DX4 .96in(126mm)H
.
STANDARD ACCESSORIES
Refer to tabbed pullout sheet at the end of the ReplaceableMechanical
Parts section .

Introduction

1 . Attach a tag
to
the TR
503 that shows : name and
This section describesthefunctionsoftheTR503/492

address of firm, name of
person responsible for the
TR 503,
serial number, and a description
of the service
system, the installation procedure, the controls and
required .
connectors,
and the checkout procedure .
About the Tracking Generator
The TR 503 Tracking Generator is a
two-wide instru-
ment that
plugs into a TM 500 mainframe . It provides the
492 Spectrum Analyzer with
a level-calibrated RF signal
source thattracksthe input frequency
of the analyzerfrom
100 kHz
to
1
.8 GHz . The output of the TR 503 is adjustable
from 0 to -59 dBm in 1
dB steps . The TR 503/492 system
can be used to display the frequency
response of various
devices such as filters, amplifiers, two-way transmission
lines, etc
., by connecting thedevices between the TR 503
output and the 492 input .
If the 492 has
Digital Storage, it is possible to con-
veniently measure frequencies
appearing on thescreen of
the 492 by using a DC 508 Frequency
Counter connected
to
the
AUX RF OUTput of the TR 503 .
These three
instruments
may be used to check frequencies
appearing
in RF
spectra as well as making closed-loop response
measurements
.
Installation
OPERATI NG I
NSTRUCTI ONS
The TR
503 was inspected both mechanically and
electrically before shipment
. It should be free of mars or
scratches and electrically meet
or exceed all
specifications .
To confirm this, inspect the instrument
for
physical damage incurred
in transit and test the electrical
performance by following the
Operators Checkout
Procedure
in this section . If there is a
problem, contact
your local Tektronix
Field Office or representative .
Install
the TR 503 by aligning its guide
rails with the
tracks of mainframe
compartment and then
pushing the
TR 503 into the
compartment until the instruments'
front
panel is flush with the front
panel of the mainframe .
To
remove the TR 503, pull the
release latch on the lower left
front panel . Refer to Fig . 2-1 .
Repackaging
Section 2-TR 503
2 .
Obtain a shipping container
made of heavy cor-
rugated
cardboard or wood . To allow for
cushioning,
make sure that the
inside dimensions are no less
than 12
by 12 by 18 inches (300
by 300 by 450 mm) . This
container
should have a carton test
strength of no less than 275
pounds
(605 kg) .
3 .

To protect the finish
of
the
TR 503, wrap it in heavy
paper or polyethylene . Protect the
front panel with
urethane
foam or strips of cardboard
.
4 .
Cushion the TR
503 by tightly packing urethane
foam or dunnage between the TR
503 and the shipping
container . Allow
at least 3 inches
on
all
sides .
5 . Seal the container with
shipping tape or an
in-
dustrial stapler .
If there are any
questions, contact the
nearest
Tektronix
Field Office or
representative .
Functions of the Controls
and Connectors
Front Panel Controls
:
OUTPUT LEVEL
: Selects 0 to 59 dB of attenuation in
1 dB steps . Controls the level
of the RFOUTput but
does
not
affect the AUX RF OUTput .
VAR dB :
Provides a 0 to 2 dB range of attenuation
that
is continuously
variable . Controls the level of
both the RF
OUTput and the AUX
RFOUTput .
Save and
re-use the TR 503 shipping
container . If the

TRACK ADJUST :Adjuststhefrequencyoffset
between
original container
is not available or damaged,
repackage

the TR
503 RF OUTput and the input
frequency of the 492
the TR 503 as follows :

Spectrum Analyzer .

Operating Instructions-TR
503
RF OUT . A 0 to -61
dBm RF signal source that tracks
the input frequency of the spectrum analyzer .
This must
be terminated in 50 fl to maintain
flat response .
AUX RF OUT : A RF signal source for
auxiliary equip-
ment such as a frequency counter
. This must be ter-
minated in 50 f2 to maintain
flat response .
2nd LO IN : This accepts a signal from the 2nd local
oscillator of the492 Spectrum Analyzer
.
2-2
Rg . 2-1 . Plug-in module Installation .
Output Connectors :

Operators Checkout Procedure
Prepare the TR 503 .'492 system as follows :
(1735-2)3526-13
a .
Insert the TR 503 and frequency counter into a
TM 500 mainframe .
b .

Using the coaxial cables supplied
with the standard
accessories, connect the
1st
LO
output port of the 492 to
the 1st LO
IN
of
the TR 503 . Connect the 2nd LO output
port of the 492 to the 2nd LO
IN of the TR 503 .
Input Connectors :

c .

If a frequency counter such as the DC 508 is used,
1st LO IN : This accepts a signal
from the 1st local

connect the AUX RF OUTput of
the TR 503
to the 50
O
oscillator (LO) of the 492 Spectrum
Analyzer .

input of the counter .
d .

Compare the connections with Fig . 2-2 . The dotted
lines are used to show the connections used in the

FrequencyMeasuring
Procedureattheendofthissection .

b .
Adjust the TR5D3 OUTPUT LEVEL and VAR dB
The492 Spectrum
Analyzer is shown connected to either

controls sa the 492 display lies on the -4 dBm line (2
r

an
antenna or a device under test .

divisions below the top of the screen) .
e .
Switch on power to all units . Warm up the in-
struments for
at
least a half-hour . ( Procedure 4, Measuring
Frequency, requires a two-hour warmup .) Set
the
Time/Div control on the 492 to Auto .
T

1 . Check Flatness
a . Set the 492Re#erence
Level to D dBm, the Frequen-
cy to 10D MHz, the
Span/Div
to
1 MHz,and the Vertical
Display to 2 dB/Div .

d . Reset the 492 Vertical Display to 1D dB/Div .
O
r
Frequency
TR503

III
O
I
Counter

,

1st 2nd
Operating Instructions--TR 503
c .

Increase the 492 Span/Div to
Max . Confirm that the
response of
the
TR 503/492 system
is within ±2 .25 dB
with reference to
1D0 MHz over the 100 kHz to 1 .8 GHz
span
.
O
LO LO
O
Q v
492 Spectrum Analyzer
O
.". .
. . . .
" " " "
" "
" Out Aux
.
"

O

RF

1st
LO
"

Out
" O

i
d

2nd LO

/
i
N to BNC
t
Adapter
1
I
1 `-_
,~
I
b
In

Out
0
N to BNC

3mm,
Adapter

SMA to BNC

D .U.T .
Adapter
fig . 2-2 . TR 5031492
System with Frequency Counter .
RF Source
aszs-z

Operating Instructions-TR503
2 . Check
Output Level

e . On the 492, press Auto Resolution and
rotate
a .
Set the TR 503 OUTPUT LEVEL
and VAR dB to

Span/Div clockwise intothe MHz range . Setthe
Reference
0 dBm
(VAR dB is fully clockwise) .

Level to 0 dBm . Set the TR 503
OUTPUT LEVEL to 0 dB .
b . Decrease the
OUTPUT LEVEL to -50 dBm
in
-10 dB
increments while decreasing the 492 Reference
Level in equal
increments . Check that the display
level
remains
constant .
c . Return the
OUTPUT LEVEL to 0 dBm .
d . Set the
492 Reference Level to 0
dBm, the
Spand/Div
to 1 MHz, and the Vertical
Display to 2 dB/Div .
Set the 492 display on a
horizontal line by slowly adjusting
the TR 503 VAR dB
control .
e . Decrease the
TR 503 OUTPUT LEVEL i n 1 dB steps
and check that the492 display decreases accordingly
.
f .
Return the TR 503 OUTPUT LEVEL and VAR dB
controls to 0 dBm .
g . Rotate the VAR dB
control through its range and
check that the
display on the 492 decreases in accordance
with the
calibrations on the VAR dB scale .
3 . Tracking Adjustment
This procedure
adjusts the TR 503 output frequencyto
match the
input frequency of the492 Spectrum Analyzer
.
a . Set the 492
Reference Level to -20 dBm anal the
Frequency to 100 MHz . Set the Vertical
Display to
2 dB/Div .
b . Set theTR 503
VARdBtoO(fullyclockwise)andthe
OUTPUT LEVEL to -20
dBm .
c .
Decrease the Span of the 492 until it is zero ;
the
upper right corner of the crt will read
10 MS/ . Slowly
decrease the Resolution Bandwidth
(the outer knob of
Span/Div) while adjusting
the TR 503 TRACKING AD-
JUSTfor maximum trace height
. Whenthe492 Resolution
Bandwidth
is-at the 100 Hz minimum setting (1 kHz in
non-phaselock 492s), make a final correction
to the
TRACKING ADJUST . Maximum trace
amplitude on the
492 screen indicates that
the TR 503 and the 492 are
matched
.
4 .
Measuring Frequency
A 492 Spectrum Analyzer with
digital storage (option 2)
is recommended for this
procedure . Referring to Fig . 2-2,
connect and operate the system
as follows :
a . To measure
the frequency response of a device
under
test (DUT), close the circuit between the spectrum
analyzer and the tracking generator by
connecting the
DUT between the 492
RF Input and the TR 503 RF
OUTput . The DUT musthave50
C terminations on both
input and output for
this measurement to be valid .
To
measure frequencies in an RF spectrum,
connect
the 492 RF Input to the RF source . Disconnect
the 50 S2
cable from the TR 503 AUX
RFOUTput to prevent stray
radiation from this
cable affecting the accuracy of the
measurement . (The cable is reconnected after thedesired
spectra is stored in the
digital memory of the 492 .)
b .
Adjust the 492 Reference Level, Frequency,
and
Span/Div to display the frequencies of
interest on the crt .
Deactivate View B,
leaving only View A lit .
c . Press Degauss on the492 and recenter
the display
with the Frequency control
.
d . When the desired spectra
is present on the492 crt,
press Single
Sweep, Save A, and Readout . Switch the
Time/Div control to MNL (one click counterclockwise) .
If
the 50 f2 cable from the TR 503 AUX
RF OUTput is
disconnected, reconnect it before the next step
.
e .
The 492 Peak/Average knob now controls the
vertical movement of thecursor line and
whilethe Manual
Scanknob controls the horizontal
movement of the bright
spot
.
Place
this spot on the frequency of interest and read
the value from the frequency counter .
f .
Repeat step
"e" for other frequencies on the crt
display . The measurement error of this procedure is
directly related to the frequency drift of the 492
between
steps "d" and "e" . The accuracy is
improved if measure-
ment times are kept
short .
g . When finished, restore the TR 503and the 492 to
previous settings . For the 492, return Time/Div to Auto
(one click counterclockwise), and press Free Run, Save
A,
d . The TRACKING ADJUST is
now set for the 492 in

View B, and Readout . Move the cursor to either thetop or
the test set-up .

If a different
492 is substituted, the

bottom of the screen, depending on choice of
average or
TRACKING ADJUST will have to be reset .

peak detection
.
2- 4

THEORY OF
OPERATION
Section 3-TR 503
This section describes
the functions of
the major

In practice, the
TR 503 RFOUTput is
a swept, rather
circuits and their
relationships to each
other . Thedescrip-

than
fixed, frequency . In addition,
when the 492 is set to
tions are intended
for the
knowledgeable user and
for the

spans of 100 kHz/Div or
more, the 1st LO is
controlled by
technician servicing
the instrument .

the Frequency and Span
voltageswhilethe2ndLOissetto
2 .182
GHz . When spans of
50 kHz/Div or less are chosen,
the 1st LO
is phase-locked (in instruments
that have this
The section begins with thegeneral
description,
follow-

option)
and the 2nd LO is
controlled bythe Frequency
and
ed by the block
diagram description,
and ending with a

Span voltages .
When the 2nd LO
exceeds its tune range,
detailed analysis
of the major circuits
. Voltage data, signal

the
1st LO is re-locked to a
different frequency,
permitting
levels, and frequencies are provided
in the diagrams
to

the 2nd LO to
recenter its tune range .
clarify
understanding of circuit functions
.
BLOCK
DIAGRAM
DESCRIPTION
GENERAL
DESCRIPTION

The 2 .072 GH . oscillator
is phase-locked
110 MHz
below the 2nd LO
frequency . The 110
MHz difference is
This
subsection begins with a quick
review of the signal

maintained
by dividing it down
to 55 MHz and comparing
flow
through a 492
Spectrum Analyzer . The next
two

it to a 55 MHz
crystal-controlled oscillator .
A voltage that
paragraphs
"freeze" the swept
output of the TR 503 at

is proportional
to the phase difference is
fed back as an
500 MHz and describe
the signals appearing at the
major

error signal
to the 2 .072 GHz
oscillator, keeping it locked
points of the
TR 503/392 system .
The last paragraph

110 MHz below the 2nd LO
input signal .
discusses
details not
.immediately apparent
from the
preceding discussion
. This subsection
is intended to be
used
with Fig . 3-1, the System
Diagram . The 2 .072
GHz signal is passed through
a directional
coupler
which couples some of
the signal to the phase-
locked loop and
directs the remaining
energy through a
The 492 Spectrum
Analyzer mixes the input signal
with

leveling
attenuator (setting
the desired amplitude), a
the 1st LO (local
oscillator) frequency, obtaining
a 1st IF

2 .2 GHz low-pass filter
(attenuating harmonics
and upper
(intermediate frequency) of 2 .072
GHz . This IF is then

sidebands from
the output mixer),
a second leveling
mixed
withthe2ndL0,obtaininga2ndlFat110MHz
.This

attenuator, an isolation
amplifier, and a6dBattenuator
product isthen
mixed with the100 MHz 3rd LO,
obtaining

feeding into
the output mixer .
The isolation amplifier
a final
IF at 10 MHz . This signal
is passed through a VR

assists the low-pass filer in
preventing energy from
the
(variable resolution)

stage, a log amplifier, and
a

output mixer from
leaking into the 2 .072
GHz oscillator
peak/average detector
. The detector
output is either

and the
phase-locked mixer
circuit .
digitized
and stored or sent
directly to the video amplifier
of
the crt .
At spectrum analyzer
frequencies near zero,
the 1 st LO
is near 2 .072
GHz . This frequency
will disable the phase
The following
signals are found
within the 492 Spec-

lock if leakage from the output
mixer is present .
The 6 dB
trum Analyzer when 500
MHz is applied to the input
. The

attenuator
serves to smooth the output impedance
of the
2 .572 GHz
signal of the 1st LO is
mixed with the input,

isolation
amplifier, improving
the load seen bythe output
obtainingalstlFof2 .072GHz
.ThisIFisthenmixedwitha
mixer .
2 .182 GHz
signal from the 2nd LO,
obtaining a 2nd IF at
110 MHz . This IF is sent to
the remaining stages
ofthe492
(described above)
.
The
following signals are found
within the TR 503
Tracking Generator
when it produces a 500
MHz output .
The TR 503
accepts the 2 .182 2nd LO signal and
generates
a
phase-locked signal 110 MHz
lower-at 2 .072 GHz . This
signal is then mixed with
the 1st LO signal of 2 .572
GHz,
obtaining an 500
MHz output . This signal is
levelled and
sent to the
RF OUTput, the DUT (device
under test), and
the 492 Spectrum Analyzer .
The conversion
loss through the output
mixer is
essentially constant with frequency .
The amplitude level
of the IF signal tracks
the amplitude level of
the rf signal
with 6 to 8
dB of loss . The I F level is
set by controlsi ng the rf
level input level . A constant output
level is maintained by
a
feedback loop
that controls the attenuation
of the
2 .072
GHz signal path . The
forward signal path through
the attenuator
affects the amplitude at the
level detector .
The
feedback path applies this
amplitude to the leveling
attenuator as a
correction signal so the output
remains
constant
over the frequency
range of the TR 503 .

Theory of Operation-TR
503
492 SPECTRUM
ANALYZER _

VIDEO AMPL
DGTL
STORAGE
500 MHz

ATTEN .

LPF

MIXER

Z " O~~Hz

MIXER

il~~ z

MIXER

lr
R F
I~
IF

IF

VR LOG DET CRT
The input signal from the
1st LO is 4 dBm or more . This
is
amplified by the 2 .1 GHz to 3 .9 GHz
amplifier
so
the
level intothe LO port of the
output mixer is between 7 dBm
and
10 dBm . Harmonics of the input signal are
attenuated
by the 2 .1 GHz to 3 .9 GHz bandpass
filter . Re-entrant
modes of this filter are
eliminated byalow-passfilter . Two
ferrite isolators provide correct
termination for the
3-2
DU .T .
~ 100 kHz N

I

L
50kHz

I

LO
CONTROL

MICROCOMPUTER

-- ;-
~1
..
1sT LO

~ .
Zlvu LO

~ 3ao LO
z .572 GHz

2 .l8zraHz

100
MHz
U
i5T LO OUT

U
2ND LO OUT

U
CAL OUT
,2 .182C,Hz

TR503 TRACKING GENERATOR
LPF I
~

LPF
~
4-CAVITY FLTR
110 MHz
AMPLIFIER
OUTPUT
INPUT
MIXER MIXER
-2

TRACKING
ADJUST
u
A
~

LPF
~

LEVELER

~~

DETECTOR

~i -------
OUT
2 .072 GHz

55 MHz
Fig . 3-1 . TR 503/492 System Diagram .
amplifier and bandpass filter . These isolators and the

C
amplifier prevent interaction between the output mixer
and the 1st LO . This isolation and
afilter prevent signals in
the 0 to 1 .8 GHz and 4 .2 to 6 GHz range from entering the
spectrum analyzer . Leakagefrom these signals would
degrade the sensitivity of the analyzer and lift the display
baseline .

The 2 to 4 GHz isolators have less than 0
.4 dB loss in

The leveling attenuator and
normalizing attenuator are
the forward direction and
more than 20 dB loss in the

identical
. The forward gain of the isolation amplifier is
reverse
direction . The 4 .5 GHz tubular low-pass filter

7 dB . the reverse gain is -20 dB or less . This amplifier
attenuates the re-entrant mode
of the interdigitated

drives the mixer through a 5 dB attenuator
.
bandpass filter (at the third multiple of its passband) .
This
bandpass filter attenuates
harmonics of the2 .1 to3 .9 GHz
signals that are generated by the spectrum analyzer and

The lower conversion frequencies from the mixer pass
the saturated 2 .1 to 3 .9
GHz amplifier . This filter also

through a 3 dB attenuator and a low-pass
filter
to
the
attenuates 0 to 1 .8 GHz and 4 .2 to 6 GHz
signals that

~n+ideband
amplifier . The 3 dB attenuator provides a
return from the output
mixer of the TR 503 .

wideband (to 6 .6 GHz) termination for the
mixer and the
low-pass filter attenuates
2 .072 GHz and higher products
from
mixer . This filter is flat up to 1 .8 GHz and cuts off
above that with a sharpnotch
at 2 .072 GHz . The wideband
The mixer requires about 5 mW into
the LO
port
and a

amplifier provides 40 dB of gain .
nominal -24 dBm into the rf port . The IF output of the
mixer is about -30 dBm over the
frequency range of 0 to
1 .8 GHz .

The wideband amplifier
sends its output to a second
1 .8 GHz low-pass filter . This filter rejects harmonic distor-
tion products of the
amplifier . (Amplifier distortion is
The 2nd
t_O signal from the spectrum analyzer is

dependent on
signal frequency and level .) The filter
applied through a 20 dB attenuator, a 2 .2 GHz
low-pass

output is sent to the power divider and peak detector
.
'

filter, and a four-cavity
bandpass filter to the mixer . The
2 .2 GHz low-pass filter attenuates or blocks
re-entrant
-

modes (at 6 .546
and 10 .91 GHz) from the four-cavity

The
level detector
is a directional peak detector that
bandpass filter . The passband of this filter is
narrow

senses forward power but not reflected or reverse power .
'

enough to attenuate the
2 .072 GHz oscillator signal,

The forward power is
load-independent . The power loss
_

preventing

this

signal

from

entering

the

spectrum

through the divider is 6 dB for the RF OUT connector and
analyzer . Four tuning
screws, onefor each cavity, serve to

9 .5 dB for the AUX RF OUT
connector . The output
.~

adjust the response of
the bandpass filter . The signal then

attenuator provides calibrated 1 dB and 10 dB steps of
passes through a two-diode balanced
mixer, where it is

attenuation for the RF OUT
connector .
-

mixed with
the signal from the 2 .072 GHz oscillator . The
position of the mixer affects the
response of the filter by
controlling
mixer balance and coupling .

Bias and Leveling Loop
Circuitry
Theory of Operation-TR 503
DETAILED
DESCRIPTION

The 2 .072 GHz oscillator sets the frequency by coupl-
ing a resonant micro-strip transmission line to the collec
RF and
Microwave Circuits

for of the
common-base oscillator . 20 MHz of tuning is
available by varying the collector voltage, which in turn
The
RF section consists of microwave
assemblies that

alters the collector-base capacitance of
the
oscillator
includemicrowaveintegratedcircuitsinmetalenclosures
.
transistor
.
Because
repair
of
these assemblies requires
special
techniques and equipment we
recommend replacing the
entire assembly if
failure should occur . The
diagrams for

The 2 .072 GHz
signal

is fed from the directional
these assemblies show only basic configurations
and

couplertoaPINdiodeattenuatorwiththediodeoperating
illustrate functions
and do paths between external con-

as a variable resistor . The
circuit is a "T" attenuator with
vectors .

the
resistance of the diode inversely proportional to the
current . As the current
increases (from 0 to 5 mA) the
resistance
changes from open-circuit to 5 II . This variable
The input signal from the spectrum
analyzer is

allows initial adjustment of
operating range .
amplified to a level of 10 mW by
the 2 .1 GHz to 3 .9 GHz
amplifier . The
nominal gain of the amplifier is 6 dB
.
Because of gain characteristics,
this amplifier operates as

The 2 .2 GHz
low-pass filter attenuates harmonics of
a limiter and provides a
relatively constant output over a

the 2 .072 GHz signal in the forward
direction
as
well as
wide
range of signal levels . This limiting action
provides a

higher

frequencies

that

leak

through

the

isolation
constant LO signal
level to the output mixer .

amplifier from the output mixer .
Bias for the microwave and isolation amplifiers is
supplied by
five bias supplies (0150, U160, U170, U180,
The 110 MHz I Fsignal from
the mixer is passed through

and U240) on the Bias circuit board . The bias circuits and
a
directional coupler and an all-pass network to
the

rf amplifiers are connected by a feedback loop with the
110 MHz amplifier .
The all-pass network provides correct

collector load current of the rf amplifier sensed by the
termination for the directional
filter .

input resistor (R) of the operational
amplifier . The voltage
3-3

Theory
of Operation-TR 503
across this
resistor is compared to a +10
V reference . The

Phase Lock Loop
op
amp output drives the base
of the rf amplifier, setting

The 2 .072 GHz oscillator is phase locked 110
MHz
the bias and
holding the collector resistor
voltage at

below the 2 .182 GHz
2nd LO signal from the spectrum
+10 V .

analyzer . The 110 MHz difference product
from the input
mixer is sent through
five stages of amplification, divided
down to 55
MHz, and compared to a 55
MHz signal from
The load resistors for the output
amplifiers are R140,

the crystal oscillator . A
voltage that is proportional to the
R162, R174,
and the resistor iri'the microwave assembly

phase
difference between the two 55
MHz signals is fed
for the final amplifier stage .
These resistors set the

back to the 2 .072 GHz
oscillator, forcing its output to be
collector
currents of the first two amplifiers at 10
mA, the

exactly 110
MHz
below
the 2 .182 GHz 2nd LO
signal .
third amplifier at 20 mA, andthe
final at
30
mA . The load
resistor (R242) for the
isolation amplifier setsthe collector
current at 15 mA .

The 110 MHz signal is
sent through three stages of
common-emitter
amplification, transistors 0550, 0505,
and 0510 . The collector of 0510
is coupled totransformer
T520,
which provides a differential signal for
the next two
The+10 V reference for the bias circuits is
generated

stages .

Differential

amplifiers

U540B

and

U540A
by a voltage regulator circuit
using op-amp 0250 . The

successively amplify the
110 MHz signal and send it to a
reference for the
regulator is a 6 .2 V Zener diode (VR258)

divide-by-two
counter, 0550 . Thetotal gai
n
is
about 60 dB
which sets the voltage level at the
inverting input of the op

for an input below -45 dBm
; from -45 dBm to +10 dBm
amp . This is
amplified to +10 V . The bias current for the

the output remains relatively constant
. 0550 provides a
6 .2 V Zener is provided by the
+10 V reference . A 7 .5 V

55 MHz output which is sent
to the phase/frequency
Zener (VR250) is connected from the output to
the+l5 V

detector
U545 . This device compares the signal
fromU550
supply ; the Zener is used to
start the +10 V reference . As

tothesignal from the55 MHz
crystal-controlled oscillator .
soon
as the output of the regulator exceeds +7 .5
V the
Zener ceases to draw
current and is isolated from
regulator
operation .

The

reference 55 MHz

signal
from the crystal-
controlled oscillator U520A is
sent through buffer U520B
which is connected
to the phase/frequency detector U545 .
Diode CR250, connected between ground and the

The crystal operates on the
third overtone which is
+15 V line, protects the microwave
circuitryfrom acciden-

selected by
the low 0 resonant circuit tuned by
C524 . The
tal application
of negative voltage .

frequency can be tuned
through 55 MHz by varying the
voltage bias on
the variable capacitance diode CR526 .
This bias is set by the
front panel TRACKING ADJUST
control R10 . (Voltages for the adjustment
aresupplied by
The leveling loop consists of a
level detector and a

U365B) . This control
allowstheoperatortosettheTR 503
temperature-compensating
diode driving a differential

to the
spectrum analyzer input frequency or offset
the
amplifier . The output of this amplifier
drives a second

frequency by a slight amount
.
amplifier which setsthe leveling
attenuator . With no power
into
the detector, the output of the diodes is closeto 0 .4
V .
The diode outputs drive
the i nputs of differential amplifier

The output of the phase/frequency detector is sent to a
0200 .
The output of the compensation diode is summed

compensating amplifier U365A
and 0420 . The compen-
with a voltage set by the leveling
control circuit . The

sating
amplifier has a buffered output that drives
the
temperature
compensating diode corrects for detector

collector of the 2 .072 GHz oscillator
.
0440
limits the
output variations induced by temperature
shifts . As power

current if the output is
inadvertently shorted .
into
the
detector
increases, positive signal excursions are
clamped to +0 .4 V .
Transistors 0445 and
0430 arethe active components
of an
anti-latch circuit . When this circuit is activated, it
drives the 2 .072 GHz oscillator through
a frequency band
U200 is an op-amp
configured as an i ntegrator . Its

until it locks to the 2nd LO of the spectrum analyzer . When
output is a correction signal depending on the difference

the tune voltage is +3 V or less,
0445 is cut off . The
between the reference and level detector
. The reference

collector voltage
rises towards Vccand allows C432 to
voltage is set by a voltage divider network composed by

charge through R438 and R444
until it
is
0 .7 V above the
R225,R220,R222,andthefrontpaneIVARdBcontroLMin

gate
potentialof0430(thisisaprogrammableunijunction
Output Level adjustment R225 setsthe minimum level (or

transistor) . When this transistor turns
on, the charge on
offset constant) . Max Output Level adjustment R220
sets

the capacitor C432 is transferred to the cathode and sent
the range of
the VAR dB control to cover 2 dB . The VAR dB

to the
non-inverting input of operational amplifier U365A
Linearity adjustment shapes the output
level
to
maintain

(C428 also acquires a charge) .
The output of the compen-
calibration of the VAR dB control . The reference for the

sating amplifiers steps positive to about +18 V, then
output level control circuitry is set by a 6 .2 V Zener
diode

decays linearly towards 0V . As
the tune voltage passes
(CR262) .

through a range that will lock the 2 .072 GHz oscillator to

7i

Theory of Operation-TR 503
the 2nd LO of the spectrum analyzer, the phase lock

regulators are short-circuit protected
with foldback
regains control . If the oscillator fails to
start
or
lock, the

current limiting .
cycle is
repeated .
For example : the -15 V supply (U390) current sensing
0410 is the 25 mA current source for the 2 .072 GHz

resistor is R394andthefoldbackcircuitincludesR398and
oscillator . 0480 is the output of
the +20 V supply for the

8396 .

If the current delivered to the load

becomes
compensation amplifier circuitry .

excessive, thevoltage drop across R394 will be enough to
turn on the current-limiting transistor 0395 . This
Power Supply Regulators

decreases the current through the pass transistor 0390
and limits the current
to
the load . Foldback current
is
Three power supply regulators (U350, 0370, and 0390)

50 mA (1 V/20 i'2) and power dissipation in the pass
provide +15 V,
+15
.1
V,
and
-15 V respectively . These IC

transistor is about 1 W (50 mA X 20 V) . If the
-15
V line
is
regulators use external pass transistors that are located in

shorted to ground, the current will be limited to 35 mA
the TM 500 mainframe
for the positive supplies and on the

(0 .7 V/20 f2) andthe power dissipation to 1 .2 W (35 mA X
Mother board of the TR 503 for the negative supply . All

35 V) .
L
" a

Introduction

History Information
Calibration
consists of a Performance
Check
and
an

The instrument and manual are periodically evaluated
Adjustment Procedure .' The Performance Check

and revised . If modifications require changes in the
describes procedures to verify that the instrument is

calibration procedure, history applicable to earlier in-
performing properly and meets the specifications listed in

struments is included as a deviation within
a step or as a
Section 1 . All tests can be performed without accesstothe

sub-part to a step .
interior
of
the instrument . The
Adjustment part provides
instructional steps required to recalibratethe instrument
circuits . After
adjustment, the
performance
should be
checked by the procedure described under the Perfor
mance Check part . We recommend only adjusting those

Equipment Required
circuits that do not meet performance specifications
.
The table
below lists the test equipment recommended
for the Performance Check and Adjustment Procedure .
The limits, tolerances, and waveform illustrations are

The
characteristics specified are the minimum required
aids to calibrate
the instrument and are not intended as

forthechecks . Equipment that is substituted mustmeet
or
performance specifications .

exceed these
characteristics .
Equipment

Characteristics
Power Meter

Measurement Range, up
to
0 dBm .
Test Spectrum
r
Analyzer
CALI B RATI
O
N
Table 4-1
EQUIPMENT REGIUIRED
Performance Check
Adjustments
General Microwave Model 454A .
Hewlett Packard Model 435A with 8484A
power sensor .
Tektronix
492
All
of
the items
listed above as well as the following are required for the Adjustment Procedure
.
DC Voltmeter

I 0 to 50 V Range .

I Tektronix DM
501
A,
502A, 505 of the
TM 500-Series .
Frequency Counter

Measurement Range, to 55 MHz . Stability

Tektronix 7D14 for the 7000-Series
or the
1 part in 10 - ', Resolution
200 Hz .

DC 501, 503, 504, 505A, 508 of the TM 500-
Series .
Option
1
is required for the TM 500
instruments .
Oscilloscope

I Sensitivity 5 mV to 5 V, Bandwidth

I Tektronix 7000-Series
.
100 MHz or more .
1 X Probe

1100 MHz .

I TEKTRONIX P6062B .
10X Probe

1100 MHz .

I TEKTRONIX P6062B .
Plug-In Extender for

Tektronix Part No .
TM 500 instruments . I

1067-0645-01 .
Recommendation andUse
Section 4-TR 503