Tektronix 7L12 User manual

L~~

I N ST RU CTIO N
ΜΑΝ U ΑΙ
070-1298-01
7
L 12
SPECTRUM
A N A L Y Z
ER
Serial N umber

-

'
Te k
tronix,
Inc .
t Ρ .
Ο . Box 500

Ao-

B eaverton, Orego n 97005

+

Ph one : 644-0161 t Ca b les : Te k tronix
772

W
ARRANTY
All TEKTRONIX instruments
are warrante d against
defective materials an d
workmanship for one year . Any
q uestions
with res p
ect
to the warranty should be taken up
with your
TEKTRO N IX Field Engineer or representative .
All
requests for repairs an d replacement p arts should be
directe d to the TEKTRONIX Fiel d Office or representative
in your area . This will assure you the fastest possible
service . P lease inclu d e the instrument
Type N umber or P art
N umber and Serial Number
with
all
re q uests for parts or
service
.
Specifications an dp rice change privileges reserv
Copyright @ 1972, new material 1973, b y Tektronix,
Inc ., Beaverton, Oregon . Printed in the United States of
America . All rights reser v ed . Contents of this p ublication
may not b e repro duced in any form without permission of
Te k tronix, Inca
U .S .A . and foreign T EK TR O N IX prod ucts covered b y
U
.S
.
a nd foreign p ate n ts and /or p atents p ending
.
TEKTRONIX is α registered trademark of
Tektronix, In

TA
BLE
O F CO
N TEN
TS
SE CTIO N
1

Sp ecifications

P age
Introduction
E lectrical C ha r acteristics

1-1
S
E CTIO N 2

O
p erating
I n st ru ctio n s
Introduction

2-1
Fun ction
of t he Fr on t P anel Controls and Connectors

2-1
Ge
n
eral O p erati ng I n fo r mation

2-6
P reliminary
F ro nt Pan el Setu p an d Cali b ration

2-6
P
roce
du r e
to M atc h t he71_12 to t he Oscillosco p e
Cali b rati ng t
he Swee
p
2-6
C h
ec
k and
Ad ju st L og-Am
p
Cali b ratio n 2-8
C h ec k L in M odeand
10 d B /Div O p eration

2-9
A dj ust Contrast an d C
h
ec
k B aseline Cli
pp er
O pe r atio n 2-9
U si ng t heAnalyzer
Signal Ap p lication

2-9
R esolution, Se n sitivity an d Fr e q uency S p a n
2-11
Gain Desensitizatio n N ea r 0 Hz

2-11
Selecti ng
Sweep R ate

2-11
Trigge r ing t he Dis p lay

2-12
How to Swee p t he Disp lay U sing
an E
xternal
Swee p Sou r ce

2-13
E xternal Trigge r e d Op e r ation U sing α V e r tical Am p lifie r
Plug-in U nit as t h e Source

2-14
U sing t he Cal Out Sig n al R eference fo r Accurate F r e qu ency
an d Ap p licatio n s

2-15
Applications

2-15
S E CTIO N 3

P erfo r mance C h
ec
k
Pr eliminary P re p aration

3-1
C hec k 10 dB /DI V
a nd L I
N M
od e Cali b ratio n s

3-1
C hec k t he F re q
ue n cy R ea d ou t Accuracy

3-1
C hec k Gain
Selecto
r
Accuracy an d V a r ia b le R a n ge

3-2
C h ec k O p eration of the V i deo F
ilte r 3-2
C h ec k Sen sitivity

3-2
C h ec kF or S p ur io us Sig n als ( R esi d
ual
R
esponse)

3-4
C h ec k R esol u tion Bandwi
d
t hs
and S hape F actor

3-5
C h ec k I n
ci
d ental FM

3-6
P e r fo r ma n
ce
C heck
s R equ i r i ng Test Equ i p me n t
E q u i p ment R e q
uire d 3-7
C h ec k Cali b rato r F re q
uency

3-8
C h ec k Cali brator O u t pu t

3-8
C h ec k RF Atte n uato ι Accuracy

3-9
C h ec k Dis p lay F lat n ess

3-9
Ch
ec
k Intermodu
latio n Disto r tio n 3-10
Ch ec k V ideo P rocesso r Ope r atio n
3-10
Ch ec k Time/Div Acc ur acy a nd V a r ia b le R ange

3-11
C h ec k Trigge r i ng Ope r ation and Sen sitivity

3-12
C h eck t h e H orizo n tal I npu t V oltage R equ irement

3-13
C h ec k Fre qSp an Accuracy an d L inea r ity

3-13

TABLE OF CONTENTS
(cont)
SECTION4

Calibration
Procedure

Page
Equipment Required

4-1
Time
Base
Section
Adjust Sweep Triggering

4-2
Check and Adjust Timing

4-4
Function IF Alignment
Adjust LIN Mode Baseline Offset

4-5
Adjust Gain Compensation
and
Reference
Level

4-5
Phase Lock Circuit
Phase Lock Adjustments

4-6
2nd LO and Shaper Calibration
Adjust 2nd LO Sweep Shaper Range and Center Frequency

4-8
Adjust Sweep Shaper

4-9
Voltage Memory Circuit
Adjust Voltage Memory (Cal and Offset)

4-9
Calibrate the 2nd Mixer and 2 .095 GHz Filter

4-10
Freq Span and Marker Calibration
Adjust the 1st LO Power Supply Voltage and the Freq Span
of the Oscillator

4-11
Calibrate MAX SPAN Marker

4-12
50 MHz Calibrator
Adjust the
Calibrator Output

4-13
Resolution
Adjust Bandpass of the 105
MHz
1 F Amplifier
and 300kHz
Filter

4-13
Adjust the Resolution Gain Leveling
Compensation

4-16
Preliminary Adjustment of the Gain Slope For the
Resolution Amplifier

4-17
Adjust the Post Resolution Amplifier Gain

4-17
Minimize Intermodulation Products

4-18
SECTION5

Circuit Description
Block Diagram Description

5-1
Detailed Circuit Description
Microwave
Input Circuits

5-3
105
MHz IF Amplifier, 3rd Mixer and Oscillator

5-3
10
MHz IF Amplifier and Resolution Filter Circuits

5-4
Sweep
Triggering

5-5
Sweep Generators
and Holdoff

5-5
Sweep
Span

5-5
YIG Coil Driver
and
Marker
Generator

5-5
Voltage Memory and Phase Lock Operation

5-6
YIG Oscillator Power Supply

5-6
Sweep Shaper

5-6
Function IF
Amplifier

5-7
Video Filter, Processor, Baseline
Clipper and Vertical
Output

5-8
50 MHz Calibrator

5-9

TABLE
OF CONTENTS
(cont)
SECTION6

Maintenance Information

Page
Preventive Maintenance
Cleaning

6-1
Lubrication

6-1
Transistor and IC Checks

6-1
Performance Checksand Recalibration
Troubleshooting

6-1
Troubleshooting Aids

6-2
Corrective Maintenance
Obtaining Replacement Parts

6-7
Soldering
Technique

6-7
Replacing
Square Pin for the Multi-pin Connectors

6-7
Replacing
Assemblies and Sub-assemblies Maintenance
Tools

6-7
Front Panel
Potentiometers

6-8
Removing and
Installing Freq Span/Resolution Knobs

6-8
Replacing
or Repairing the Cam Switches

6-8
Replacing the
Major Circuit Board Assemblies

6-9
Replacing the 2nd
LO Varactor Assembly

6-10
Replacing the 2 .095
GHz Filter Assembly

6-11
Replacing the 1st (YIG)
Oscillator Assembly

6-11
Replacing the 2nd Mixer
Assembly (Includes Calibration
Procedure after Replacement)

6-12
Replacing the
Phase Detector and 2nd NO Hybrid
Assembly

6-14
Replacing the Differential
Attenuator Assembly

6-14
SECTION 7

Electrical
Parts List

7-1
SECTION
8

Diagrams and
Circuit Board Illustrations

8-1
SECTION9

Mechanical Parts List and Illustrations
(Exploded View)

9-1

Fig . 1-1 . 71-12 Spectrum Analyzer

SPE CI F ICATIO N
S
Section 1-7 L
12
Introduction

Sectio
n 9, Mec h anical P arts L ist, Exp
lode d d rawi n gs an d
Th is manual contai n s
information re q uired to operate,
Accessories : Pr ovi d es informatio n
necessary to or d er re-
test, cali b rate, a n d service t h e 71_12
Spectrum Analyzer .

p
lacea b le p arts . P art L ist is cross-reference
d to t h e Electrical
T
h e manual is d ivi d e d into ten ma j or sections
;

P
arts L ist .
E
xp lo ded drawi n g s h ows
se quence of assemb ly
an d
i
d entifie d assemb lies .
Section
1, General Information an d Specifications
.
Section 2, O p eration I n structions : Information relative
to installing
and o p erating t h e i n stru m en t .
Sectio n
10, Manual C h anges an d Correctio n s
:
P
rovi d es
h istory
and
upd
ating i n formatio n for t h e
ma
n
ual in t he
form of inserts
. As t
he
ma n ual is u pd ate d
t
h
ese inse r ts are
incor p orate d
into t
he
man u al text and d iagrams .
Section 3, P erformance
C
h ec
k : P rovi d es α com p lete
p roce du re to ch ec k
operatio n al performance for an in-

Description
co m ing acce p tance c h ec k ,
o
r
any ad d itional performance
c h ec k s t h at re q uire test e q ui p
ment to verify instrument

The 7 L 12 Spectr u m Analyzer is
α d ual-wi d t h p l u g-i n
specificatio n s .

u nit,
for t h e 7000-Series Oscilloscopes
. Wh e n use dwith any
of t h
ese oscilloscopes, it d is p lays
α s pectrum of signal
e n ergy
wit
h
in any freque ncy s p an to
1 .8 GH z . T h e unit
con tai n s h orizo
n tal sweep a nd timing
circuits, fo r fre-
Section 4, Calibration P roce
d ure : Descri b es test eq ui p -

quency an d time
d omain displays, a n d also
means b y w h ic h
ment set u p anda d j ustment p
roce d ures re q uired to align t h e

an exter n
al
sweep
source can be a pp lie d to slave
t
he
71_12
instru m ents inter n al a d ju stmen ts .

to exter n al d evices,
suc
h
as α r ecor d er .
Section
5, Circuit Description : P rovi d es b asic
and
general circuit
analysis th at may b e useful w hen servicing or
o p erating
t
he
instr
u
me n t .
Section 6, Mainte n ance I n
structions : Descri b es routine
andco r rective maintenance p roce d ures
wit h d etaile d in-
structions for replacing assemblies, su b
-assem b lies, and
in d ivi d ual com p onents . An exp lo ded
d
rawing
is
p
art of
section 9 . Trou b le-s h ooting procedu res plus
general infor-
mation t h at may ai d in servici n g t h e instr u ments
are also
p
rovide d .
Section 7, E
lectrical
P
arts L ist : P rovi d es
information

F re q uency
Sp an
necessary
to or d
er
replacea b le p arts and assemblies .
S PE CI F
ICATIO N S
ELE CT R ICA L C H A R
ACT ER ISTICS
T h e
following ch aracteristics a n d
features of t he 71_12
Spectrum A
n alyzer are applica b le after
α warm
up
pe r io d of
30
minutes
or more .
Center F
requency Operating R angean
d Acc u racy
From
0 .1
MH z
to 1 .8 GH z . R ea dout accuracy
is with in
± (10 MH z + 1°/
ο
of t
he
dial rea d o u t) .
Cali
b rate d steps, i n 1-2-5 sequence, from
500
Ητ
/Div to
100 MH z/Div .
Accuracy is wit h in 5% of t h es
pan selecte d
an d li n
earity is wit h in 5%, over t h e center 8d
ivisions of α
Section 8 . Diagrams : P rovi d es functional
b loc k d iag r am

10 division d
is p lay .
and d etaile d circuit sc h ematics . P ictoral
layout d rawings,
w h ic h
s
h
ow assembly, su b -assem b ly, an d com p
onent loca
tio n s are
locate d ad j ace n t to t h e d iagram (us u ally
on t he

Two a d ditio n al p
ositio
n
s MAX SP A N an d0 provi
d
e
bac k
of t
h
e p rece d ing diagram

p age)
. W
aveforms and
ap p roximately 1 .8 GH z
(180
MH
z/Div) of span, or fixed
voltage
d ata, for trou b les h ooti ng or circuit analysis,
ar e also

fre
q uency operation, for time
domain d is p lay . Sp an is
provi
d e d a dj acent to or on t he d iagram .

con ti n uo u sly varia b le between steps .

Specifications-71_12
Dis p lay F latness

R
esolution
±1 .5 dB over any selecte d frequency
s pan , with r es p ect

F
ive resolutio n b and wi d
t
h
selections from
300 Hz to
to t he d is p lay level at 50 MH z .

3 MH z,
in d eca d e steps, are p
rovide d . B an dwid t h accuracy,
at
t
h
e 6 d Bd ow n level, is
wit h in 20% of t h e resolution
selecte
d . S hap e factor over t he
60 d
B
to 6 d B level is 4
:1 or
Dis p lay M o d es

b etter
(see
F
ig . 3-4) . Signal level
ch a n ge over t he five
L OG 10 d B /DI V : P rovi d es α cali b
rate d 70 dB d ynamic

band wi d
t
h
s is less t h an 0 .5 dB .
range .

Accuracy

wit h i n 1 dB /10 dB
to α maxim u m of
1 .5 d
B
over t h e 70 dB d ynamic range .

Sensitivity F
or Α C W Signal
Signal
+
n oise =
Twice noise in L I N
vertical mo d e (see
L OG 2 d B /DI V : P rovides
α cali b rate d 14 dB d ynamic

F
ig . 3-2)
.
T h e
followi ng sensitivity
characteristics apply at
range . Accuracy wit h i n ±0 .4 d B /2
d
B
to α maximum of

50 MH z . Sensitivity
may d ecrease
grad u ally to 2 d B at
1 .0 dB over t he 14 d B range .

1 .7 GH z
an d to
4
d B at 1 .8 GH z .
L I N : P rovi
d
es
α linear d isplay wit h in 10%, over t h e

Sig
n al L evel

R esolution B a n dwi d
t h
graticule h eig h
t .
-115 d B m

300 Hz
-108 dB m

3 kH z
R eference L evel

-100 dB m

30 kH z
-90 d B m

.3 MH z
Calibrate d levels in d eca de ste p
s, from -100 dB
m
to

-80
d B m

3 MH z
+30 d B m,

wit h i n ±2 dB .

(I n clu d es
attenuator and gain
switc h ing effects w hen t he two are
not off-setting eac h
ot h er .) R efere n ce level d eviation b etween d isplay
modes is
;

IntermO d ulat ί on Distortion (See Fig .
3-6)
less t
ha
n 2 dB from 2 dB /DI V to 10 dB /DI V and less t han

T h ird order is d
ow
n70
d B or more from two
-30 d B m
0 .5 d ivision from 2 d B /DI V to L I N . N ote : T h is d eviation is

signals wit h in any fre quency
s p a n . Seco nd or d er
is d own
α
function
of t h e oscilloscope vertical linearity .

70 dB or more from two-40
d
B
m signals .
Calibrator

Sp urious Signals F rom
Internal Sources
50 MHz ±0 .01% wit han absol u te
amplitu d e level of
-30
dB
m
±0 .3 dB, at 25 ° C .
RF
Attenuator
( R
esi d u al R esponse)
Eq ual to or less t h
an -100 d Bm, referre d
to t
he
1st
mixer in p ut .
Cali b rated 10 d B ste p s . Accuracy ;
±0 .2 d
B
or 1% of d B
Inci d
ental FM (See F ig . 3-5)
rea
d
ing, w
h ic h ever is greater .

200 H z
(P-P) maximum, w hen ph
ase loc k e d , or 20 kH z
(P-P) maximum
in 5 secon d s, w h en
ou t of ph ase loc k mo d e .
Gain
F ou r selector positio
n s, b or d ered by
α blue sector,
Stability
p rovide
30 dB of
ch
ange, in 10 dB steps, for t he
10 dB /DI V

W it h in

50 kH z,

over

α

1

h ou r p erio d
at α fixe d
d is p lay
mode
. T
h ese four, p lus fo u r a d ditio n
al
p
ositions,

tempe r at u re, w h en p h
ase loc k e d . W it h in 100 kH z
w
hen not
p rovi d e 70 d B
of
gain
ch ange for t h e 2d B /DI V
and t he L I N

p
h ase loc k e d over
α
1 h
ou r perio d , at α fixe d tem p
erat u re .
mo de d isplays .
Accuracy

is with in ±1 d B
/10 dB step to α total of

Maximum
In p ut P ower Level
±1 .5 dB w h en t he V A R IA BLE
control is in its CA L d etent
.

L inear
O pe r ation- RF attenuator at
0 dB
;
-30 dB m .
Safe In pu t levels- RF atten u ator
at 0 d B ;
+13
d B m . RF
Th e

V
A R
IA BLE

control, wit ha
p p roximately 10d13

atte n
uator at 60 dB ;
+30
dB m (1 W
average, 200 W p ea k ) .
ra n ge,
provides continuo u s gain a dj ustment
b etwee n eac h

NOTE : Th
ese are i nput levels to t he
1st mixer and t h e
calibrate d step .

power rating
of t he atte n uator .

Sweep Rate

t he SINGLE
S WEEP mode . Sweep
automatically recurs at
Calibrate d sweeps, from 10 ms/Div
(SPECTRUM posi-

the end
of sweep holdoff time in the FREE
RUN mo de .
tion)
to 1 μ s/Div (within 2°/ ο ), are
provided in 1-2-5
se q uence . Α
V
ARIABLE
control p rovides
continuous vari-

Vertical O ut p ut
Connector
ation between steps
. When the ΤΙΜΕ /DIV selector
is in the

P
rovides 50 mV
±5°/ ο vi deo signal per d
isplayed d ivision,
SPECTRUM position,
the r ange of the V ARIABLE control

about

the

CRT

vertical

center .

Source im p
e d ance

is
is increase d a p proximately
100 Χ allowing the Time/Div
to

app
roximately
1 k
Ω
. Α maximum of 50 mV
offset may b e
be increased to about 1 s/Div .

intro duced by
error f rom the mainframe
vertical centering
interface .
Triggering
Specifications-7L12
Signal
source is AC coup le d from either
the vertical
H orizontal Input
Connector
amplifier channels
or the p ower line . Frequency
range is

R eq uires α 10 V
±1 V
signal,
with α starting reference
of
approximately
15 Hz to 1 MHz . Sensitivities
for t he trig-

0 V ±1 V from
α low
impe
d ance (300 Ω or
less)
source,
to
gered modes are :
1) <0 .5 division for the Ρ - Ρ AUTO
mo de

normalize

the

external

sweep

voltage

to

the

7L12
2) <0 .3 division for the N ORM
mo d e 3) <1 .5 division
for

frequency span .