Tektronix 7L12 User manual

A][ yL,J-/'6-
Serial Number _______-.----LC
Tektronix, lnc. -IT+- P.O. Box 500 Beaverton, Oregon 97005 J&- Phone: [phone] -@- Cables: Tektronix
070-1 298-01
772

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TABLE OF CONTENTS
SECTION 1 Specifications
l ntroduction
Electrical Characteristics
SECTION 2 Operating Instructions
Introduction
Functionofthe FrontPanel Controlsand Connectors
General Operating Information
Preliminary FrontPanel Setup and Calibration
Procedure toMatchthe7L12tothe Oscilloscope
Calibratingthe Sweep
Check and Adjust Log-AmpCalibration
Check LinModeand 10
dB/Div Operation
Adjust Contrast and Check Baseline Clipper Operation
Usingthe Analyzer
Signal Application
Resolution, Sensitivity and FrequencySpan
Gain Desensitization Near 0 Hz
SelectingSweep Rate
Triggering the Display
Howto Sweep the Display Using an External Sweep Source
ExternalTriggered Operation Usinga Vertical Amplifier
Plug-In Unitas the Source
Using the Cal OutSignal Reference for Accurate Frequency
and Applicatior~s
Applications
SECTION
3 Performance Check
Preliminary Preparation
Check 10
dB/DIV and LINModeCalibrations
Check the Frequency ReadoutAccuracy
Check Gain Selector Accuracy and Variable Range
Check Operation ofthe Video Filter
Check Sensitivity
Check ForSpuriousSignals (Residual Response)
Check Resolution Bandwidthsand Shape Factor
Check Incidental FM
Performance Checks RequiringTest Equipment
Equipment Required
Check Calibrator Frequency
Check Calibrator Output
Check RFAttenuator Accuracy
Check Display Flatness
Check Intermodulation Distortion
Check Video Processor Operation
Check TimeIDiv Accuracy and Variable Range
Check Triggering Operation and Sensitivity
Check the Horizontal InputVoltage Requirement
Check FreqSpan Accuracy and Linearity
Page

TABLE OF CONTENTS (cont)
SECTION 4 CalibrationProcedure
EquipmentRequired
Time Base Section
Adjust Sweep Triggering
Check and Adjust Timing
Function IF Alignment
Adjust LINMode BaselineOffset
Adjust Gain Con~pensationand Reference Level
Phase Lock Circuit
Phase Lock Adjustments
2nd LO and Shaper Calibration
Adjust 2nd LO Sweep Shaper Range and Center Frequency
Adjust Sweep Shaper
Voltage MemoryCircuit
Adjust Voltage Memory (Caland Offset)
Calibratethe 2nd Mixer and 2.095 GHz Filter
Freq Span and Marker Calibration
Adjust the 1st LO Power Supply Voltage and the Freq Span
of the Oscillator
CalibrateMAX SPAN Marker
50 MHz Calibrator
Adjust the Calibrator Output
Resolution
Adjust Bandpass of the 105MHz
l FAmplifier and 300 kHz
Filter
Adjust the ResolutionGain Leveling Compensation
PreliminaryAdjustment of the Gain Slope For the
ResolutionAmplifier
Adjust the Post ResolutionAmplifier Gain
Minimize Intermodulation Products
SECTION 5 Circuit Description
Block Diagram Description
DetailedCircuit Description
MicrowaveInput Circuits
105MHz IFAmplifier, 3rd Mixer and Oscillator
10MHz IF Amplifier and Resolution Filter Circuits
Sweep Triggering
Sweep Generatorsand Holdsff
Sweep Span
YIG Coil Driver and Marker Generator
Voltage Memory and Phase Lock Operation
YIG OscillatorPower Supply
Sweep Shaper
Function IFAmplifier
Video Filter, Processor, BaselineClipper and Vertical
Output
50 MHz Calibrator
Page
4-1

TABLE OF CONTENTS (cont)
SECTION 6 Maintenance Information
Preventive Maintenance
Cleaning
Lubrication
Transistor and ICChecks
Performance Checks and RecalibrationTroubleshooting
Troubleshooting Aids
Corrective Maintenance
Obtaining Replacement Parts
SolderingTechnique
Replacing Square Pinfor the Multi-pinConnectors
ReplacingAsse~mbliesand Sub-assemblies Maintenance Tools
Front Panel Potentiometers
Removing and Installing FreqSpan/Resolution Knobs
Replacing or Repairing the Cam Switches
Replacing the Major Circuit Board Assemblies
Replacing the 2nd LOVaractor Assembly
Replacingthe 2.095 GHz Filter Assembly
Replacingthe 1st (YIG)Oscillator Assembly
Replacingthe 2nd Mixer Assembly (IncludesCalibration
Procedure after Replacement)
Replacing the Phase Detector and 2nd NO HybridAssembly
Replacingthe Differential Attenuator Assembly
Page
SECTION
7 Electrical Parts List 7-1
SECTION
8 Diagrams and Circuit Board Illustrations 8- 1
SECTION 9
Mechanical Parts List and Illustrations (Exploded View)
9- 1

Fig. 1-1. 7L12 Spectrum Analyzer

Section 1-7L12
SPECIFICATIONS
Introduction Section 9, Mechanical Parts List, Exploded drawings and
Accessories: Provides information necessary to order re-
This manual contains information required to operate,
test, calibrate, and service the 7L12 Spectrum Analyzer. placeableparts. Part List is cross-referencedto the Electrical
The manual is divided intoten major sections; Parts List. Exploded drawing shows sequence of assembly
and identified assemblies.
Section 1, General lnformation and Specifications. Section 10, Manual Changes and Corrections: Provides
history and updating information for the manual in the
form of inserts. As the manual is updated these inserts are
Section 2, Operation Instructions: lnformation relative incorporated
into the manual text anddiagrams.
to installing and operating the instrument.
Section 3, Performance Check: Provides a complete
procedure to check operational performance for an in-
coming acceptance check, or any additional performance
checks that require test equipment to verify instrument
specifications.
Section
4, Calibration Procedure: Describes test equip-
. .
ment setup and adjustment proceduresrequiredto align the
instruments internal adjustments.
Section
5, Circuit Description: Provides basic and
general circuit analysis that may
be useful when servicingor
operating the instrument.
Section
6, Maintenance Instructions: Describes routine
and corrective maintenance procedures with detailed in-
structions for replacing assemblies, sub-assemblies, and
individual components. An exploded drawing is part of
section
9. "'lrouble-shooting procedures plus general infor-
mation that may aid in servicing the instruments are also
provided.
Section 7, Electrical Parts List: Provides information
necessary to order replaceable parts and assemblies.
Section 8. Diagrams: Provides functional block diagram
and detailed circuit schematics. Pictoral layout drawings,
which show assembly, sub-assembly, and component loca-
tions are located adjacent to the diagram (usually on the
back of the preceding diagram page). Waveforms and
voltage data, for troubleshooting or circuit analysis, are also
provided adjacent to or on the diagram.
Description
'The 7L12 Spectrum Analyzer is a dual-width plug-in
unit, for the 7000-SeriesOscilloscopes. When used with any
of these oscilloscopes, it displays a spectrum of signal
energy within any frequency span to 1.8 GHz. The unit
contains horizontal sweep and timing circuits, for fre-
quency and time domain displays, and also means by which
an external sweep source can be applied to slave the 7L12
to external devices, such as arecorder.
SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
The following characteristics and features of the 7L12
Spectrum Analyzer are applicable after a warmup period of
30 minutes or more.
Center Frequency Operating Range and Accuracy
From 0.1 MHz to 1.8 GHz. Readout accuracy is within
* (10MHz + 1% of the dial readout).
Frequency Span
Calibrated steps, in 1-2-5sequence, from 500 Hz/Div to
100 MHzIDiv. Accuracy
is within 5% of the span selected
and linearity
is within 5%, over the center 8 divisions of a
10 division display.
Two additional positions MAX SPAN and 0 provide
approximately 1.8 GHz (180 MHz/Div) of span, or fixed
frequency operation, for time domain display. Span
is
continuously variable betweensteps.

Display Flatness Resolution
51.5 dB over any selected frequency span, with respect
to the display level at 50 MHz.
Display Modes
LOG 10dB/DIV: Provides a calibrated 70 dB dynamic
range. Accuracy within
I dB110 dB to a maximum of
1.5 dB over the 70 dB dynamic range.
LOG 2 dB/DIV: Provides a calibrated 14 dB dynamic
range. Accuracy within 50.4 dB12 dB to a maximum of
1.0 dB over the 14 dB range.
Five resolution bandwidth selections from 300 Hz to
3 MHz, in decade steps, are provided. Bandwidth accuracy,
at the 6 dB down level, is within 20% of the resolution
selected. Shape factor over the 60 dB to6 dB level is 4.1 or
better (see Fig. 3-4). Signal level change over the five
bandwidths is less than 0.5 dB.
Sensitivity For A CW Signal
Signal + noise = Twice noise in LIN vertical mode (see
Fig. 3-2). The following sensitivity characteristics apply at
50 MHz. Sensitivity may decrease gradually to 2 dB
at
1.7 GHz and to 4 dB at 1.8 GHz.
LIN: Provides a linear display within lo%, over the Signal Level
graticule height. -1 15 dBm
-108 dBm
-100 dBm
Reference Level 90 dBm
Calibrated levels in decade steps, from -100 dBm to -40dBm
+30 dBm, within *2 dB. (Includes attenuator and gain
Resolution Bandwidth
300 Hz
3 kHz
30 kHz
.3 MHz
3MHz '
switching effects when the two are not off-setting each
other.) Reference level deviation between display modes is;
Intermodulation Distortion (See Fig. 3-61
less than 2 dB from 2 dB/DIV to 10 dB/DIV and less than Ihird order is down 70 dB or more from two -30 dBm
0.5 division from 2 dB/DIV to LIN. Note: This deviation is signals within any frequency span. Second order is down
afunction of the oscilloscope vertical linearity. 70 dB or more from two -40 dBm signals.
--
Calibrator Spurious Signals From Internal Sources
50 MHz 50.01% with an absolute amplitude level of (Residual Response)
-30 dBm T0.3 dB, at 25'~. Equal to or less than -100 dBm, referred to the 1st
mixer input.
RF Attenuator
Calibrated 10 dB steps. Accuracy; +0.2 dB or I % of dB
Incidental FM (See Fig. 3-5)
reading, whichever is greater. 200 Hz (P-P) maximum, when phase locked, or 20 kHz
(P-P)maximum in 5 seconds, when out of phase lock mode.
Gain
Four selector positions, bordered by a blue sector,
Stability
provide 30 dB of change, in 10 dB steps, for the 10 dB/DIV Within 50 kHz, over a 1 hour period at a fixed
display mode. "I'hese four, plus four additional positions, temperature, when phase locked. Within 100 kHz when not
provide 70 dB of gain change for the 2 dB/DIV and the LIN phase locked over a 1 hour period, at
a fixed temperature.
mode displays.
Accuracy is within
+I dB110 dB step to a total of
Maximum lnput Power Level
51.5 dB when the VARIABLE control is in its CAL detent. Linear Operation-RF attenuator at 0 dB; -30 dBm.
Safe lnput levels-"RF attenuator at 0 dB; +I3dBm. RF
The VARIABLE control, with approximately 10 dB aetenuator at 60 dB; +30 dBm (1W average, 200 W peak). --
range, provides continuous gain adjustment between each NOTE: These are input levels to the 1st mixer and the
calibrated step. power rating of the attenuator.

Specifications-7L12
Sweep Rate
Calibrated sweeps, from 10 ms/Div (SPECTRUM posi-
tion) to 1ps/Div (within 2%), are provided in 1-2-5
sequence. A VARIABLE control provides continuous vari-
ation between steps. When the TIMEIDIV selector is in the
SPECTRUM position, the range of the VARIABLE control
is increased approximately 100X allowing the TimeIDiv to
be increased to about 1sIDiv.
Triggering
Signal source is AC coupled from either the vertical
amplifier channels or the power line. Frequency range
is
--
approximately 15 Hz to 1 MHz. Sensitivities for the trig-
gered modes are: 1) G0.5 division for the P-PAUTO mode
2) G0.3 division for the NORM mode 3) G1.5 division for
the SINGLE SWEEP mode. Sweep automatically recurs at
the end of sweep holdoff time inthe FREE RUN mode.
Vertical Output Connector
Provides 50 mV +5% video signal per displayed division,
about the CRT vertical center. Source impedance
is
approximately 1 kfi. A maximum of 50 mV offset may be
introduced by error from the mainframe vertical centering
interface.
Horizontal Input Connector
Requires a 10 V *I V signal, with astarting reference of
0 V *I V from a low impedance (300 Cl or less) source, to
normalize the external sweep voltage to the 7L12
frequency span.

Section 2-9L12
OPERATING INSTRUCTIONS
Introduction
This section describes: 1) Installation of the 7L12into a
7000-Series Oscilloscope.
2) Function of the front panel
controls, selectors, indicators and connectors. 3) General
operation information, such as; adjustments required to
mate the 7L12 to a 7000-Series Oscilloscope, signal
application to the RF input, how to use the calibrator for
accurate frequency and power level measurements, etc.
4)'
Some typical applications.
"The first steps of the General Operating information
calibratQ and check the analyzer Frequency SpanIDiv and
the display modes. These steps serve as part of an
acceptance check and describe how to obtain a display on
the oscilloscope CRT. The Performance Check section of
this manual refers to these steps as part of an acceptance
checkout procedure.
<I5 Hz to21MHz. The INTpush-button, selects the input
signal to the 7L12 as the trigger source. The LINE
push-button, selects a sample of the power line voltage as
the trigger source.
A third push-button causes the sweep
circuit to free run.
MODE
P-P AUTO: Triggering occurs at the level and slope
selected by the LEVEL and SCOPE controls. The peak to
peak trigger signal amplitude required for
INT triggering
must equal or exceed 0.5 division. If trigger signal is absent,
or beyond the amplitude and frequency limitsspecified, the
sweep will free run (after hold-off time) at the rate selected
by the TIMEIDIV selector. The LEVEL control range
adapts to changes in the triggering signal amplitude so its
range corresponds to the peak to peak signal amplitude.
Performing this Operational Checkout procedure,
is
NORM: Triggering occurs at the level and slope selected
reconi~mendedto acquaint you with the functions of the by the SLOPE and LEVEL controls. The minimum signal
controls and selectors and the overall operation of the an'plitude for triggering must equal or exceed 0.3 division
7L12. on the display. The LEVEL control selects the signal
amplitude level. Triggering does not occur, when the setting
CAUTION
of the LEVEL control is beyond the sigt~alaml?litude level.
A safety latch, in addition to the front panel release,
SINGLE SWP: After the READY indicator is ligiited,
must be released before the 7L 12 can be pulled from triggering will occur when the signal approaches 1.5
the oscilloscope compartment. The unit will pull out divisions of amplitude. Sweep is initiated as the signal
part way when the front panel release is pulled, then amplitude and slope pass through that selected by the
the spring safety latch must be pushed up before the SLOPE and LEVEL controls. The circuit must be reset by
unit will pull the rest of the way out. This safety
pushing the RESET buiron before another sweep can be
latch is located underneath the right rail near the
triggered.
front corner (see Fig. 2-1).
RESET-R EADY: A pushbutton that resets the triggering
circuit for single sweep operation. RESET-READY button
FUNCTION OF THE FRONT PANEL lights when pushed, to indicate that the circuit is ready to
CONTROLS AND ADJUSTMENTS be triggered.
Triygering LEVEL
SOURCE
A control that selects the amplitude at which triggering
Either the vertical channels or the power line may be Occurs for the various triggering modes.
selected as the trigger source, by the front panel push-
burroqs. It is AC coupled and has a frequency range from
SLOPE
'TEKTRONIX Measurement Concept booklet; "Spectrum Analyzer
Measc~rernentsTheory and Practice". Part No. 062-1334-00 is
A switch that selects the (+) positive or (-) negative
recommended treatise on a~~licationsarld measurementevaluation.
slope of the signal for triggering direction.

LOG LO(
When depressed and the FREQ
SPANIDIV setting is less than
MAX SPAN, the FREQUENCY
readout
is the center or START
of thedisplay.
slgnrrles when lighted, that a fre-
quency marker is displayed. This
marker indicates that portion
of
the 1.8 GHz span which will be
displayed when the FREQ SPAN
is reduced from the MAX SPAN
position
Frequency readout for START or Main tuning control for the fre-
CENTER of thedisplay. quency
.
FINE tuning controls that are
used in the phase locked mode
with FREO SPANlDlV
0.1 MHz -
- Select display modes.
or less. Gain selector. Switches gain in
if
10 dB steps. Blue sector appli-
Absolute level at the top of the 1
cable to 10 dB/DIV mode.
graticule with reference to the VARIABLEGaincontrol.
settings of the RF attenuator and
Gain selector.
In 10 dB/Div
Gain selector must be in blue RF attenuator seletor and read-
sector for readings to be appli- out. Switches in
10 dBsteps.
cable.
-w MAX INPUT readout changes to
1
L-
correspond with attenuator set-
7 <IO-r>
RF lnput connector. lnput im- tings.
pedance 50 ,-
. -- 4MPL
Sets the REFERENCE LEVEL to
the topgraticule line.
4i
30
A
alibrates LOG display accurac
Pull this latch tofree instrument
from the main frame interface.
Safety latch under right rail must
be released by pushing up on the
spring latch before the
7L12 will
pull completely out of the instru-
ment.
-
Fig. 2-1A. Controls, selectors and indicators that relatetothedisplay, frequency, dynamic range, and reference levels.

Selects sweep rate. The SPEC-
T R UM position provides
10 ms1Div (VARIABLE in CALI
and is used primarily for fre-
quency domain displays. AMPLI-
FIER position, is used when an
external sweep source (at the
HORlZ IN jack or Left Vert
Plug-In) is used.
.... r~iggerselectors and co ,...
I
. .
.....
....
...
...
....
Video bandpass isreducedas indi-
.
.........
.......
....
...
...
...
cated when these pushbuttonsare
...
...
...
dmressed to filter high frequency . -7
components such as noise.
Pulsed RF is stretched, when de-
pressed,
so spectra is enhanced. .
Used with wide freq spans and
resolutionbandwidths.
.:AL OUT
GGERING
....
. .
A Calibrated 50 MHz, -30 dBm
. '
source
.
Input jack for applying external
sweepfrom a recordt
VARIABLE TIMEIDIV control.
Range increased to
100 X when
TIMEIDIV selector is in SPEC-
TRUM POSITION. (Push to un-
lock
1.
Adjusts the ratio of brightness
between the clipped baseline and
the remainingdisplay.
Compensates for differences of
oscilloscope deflection sensitiv-
ities.
Controlstheamplitude (above the
baseline) of theclipped (subdued)
portion.
Position control
Used when FREQ SPAN <I00
kHzlDiv to switch phase lock on
or off.
FREOSPANIDIV selector.
VARIABLE FREQ SPAN control
(Pushedtounlock).
Pull out to uncouple RESOLU-
TIONselector from FREQSPAN1
DIV so each can be set
independently.
Safety Latch: Push up on spring
safety latch to release instrument
after
it ispart way out.
RESOLUTION selector and read-
out window.
Video output signal for recorder
Y
Fig. 2-1B. Controls and selectorsthat relatetothedisplay; sweep, frequency span, resolution, video processing andphaselock.

Horizontal Sweep
TIMEIDIV
Selects calibrated sweep rates (VARIABLE control
pushed in) from I0ms/Div. (SPECTRUM position) to
I ps/Div, in a 1-2-5 sequence. An AMPLIFIER position
allows the analyzer to be swept from an external source.
The SPECTRUM position provides a calibrated
10ms/Div sweep rate and increases the range of the
VARIABLE control to IOOX, which allows the TimeIDiv to
be increasedto approximately
1 sIDiv for spectrum analysis.
The AMPLIFIER position is used to sweep the unit from
an external sweep source which can be applied through one
of the Vertical Amplifier units or through the HORlZ IN
connector on the 7L12. External sweep may be used to
slave the spectrum analyzer to a recorder or other external
device.
VARIABLE
Provides continuous adjustment over the -I"IME/DIV
range. The VARIABLE control range is increased from 3X
to 100X inthe SPECTRUM position.
SWEEP CAL
Calibrates the amplitude of the sweep voltage to the
FREO SPANIDIV circuits and compensates for differences
indeflection sensitivities between oscilloscopes.
HORlZ POS
Adjusts the horizontal centering of the display.
HORlZ INJack
Used to apply the horizontal (sweep) drive directly,
from a chart recorder or other device, to the 7L12
horizontal circuits when the TIMEIDIV selector is switched
to the AMPLlF IER position. Requires a sweep voltage of
0 V to 10 V '1 V, from a low impedance source. The
k1.0 V tolerance, at the upper end, is used tocalibrate the
external voltage ramp, making the frequency span of the
7L12accurate.
VERTICAL Coritrol and Output Connector
VERT PUS
Positions the CRT beam vertically.
VERT OUT Connector
Provides +50 mV of video signal per displayed division.
The amplitude and polarity of this signal
is relative to the
graticule vertical centerline. Source impedance
is about
1 kfl. The signal can be used to drive an external recorder.
Display Controls and Selectors
BASELINE CLIPPER
Controls the vertical amplitude of that portion (baseline
plus signal) of the display that
is decreased or subdued in
intensity.
CONTRAST
Adjusts the brightness ratio between the clipped (sub-
dued) baseline and the unclipped display. Display intensity
is set by the oscilloscope Intensity control.
VIDEO FILTERS
Three filters (30kl4z. 300 Hz and 3 Hz) can be switched
in to restrict the video bandwidth and reduce high
frequency components. Two push-buttonsselect 30 kHz or
300 Hz when depressed individually and 3 Hz is selected
when both buttons are pushed in.
VIDEO PROCESSOR
Enhances the visibility of pulsed RF signals within wide
frequency spans and resolution bandwidths by stretching
the fall time of pulsedsignals.
FREQ SPANIDIV
Selects the frequency span (0.5 kHz1Div to 100 MHz/
Div in a 1-2-5sequence) for the display. The VARIABLE
control must be pushed in for a calibrated display. Two
additional positions, MAX SPAN and 0 are also provided.
The MAX SPAN position, increases the frequency span to
-
approximately 1.8 GHz. A frequency marker notch is also
displayed to indicate what portion of the spectrum will be
displayed when the FREQ SPANIDIV
is reduced. The 0
position converts the analyzer to a tuned receiver, for time
domain display. Time analysis of signal characteris~ics,
within the bandwidth capabilities selected by the RESOLU-
TION setting, can then be analysed.
CAUTION
The FREQ SPAN knob provides ease in switching;
however, if excess torque is appliedafter the switch is
in either its full
CW or CCW position, the aluminum
-
bushing inside the knob may slip. This will misalign
the coupling betwccn the RESOLUTION and FREQ

SPAN selectors. If the coupling is misaligned, the
selectors will double detent or switch withagrinding
noise. Refer to Knob Removal and Installation
instructions in the Maintenancesection of the manual
for realignment.
VARIABLE (FREQSPANIDIV)
Push-push type switch and control. When it is out of its
CAL detent, the control provides variable frequency span
between each step of the FREQ SPANIDIV selector. The
control must be in the CAL detent for calibrated
FRf Cl
SPAN displays.
RESOLU'TION
Selects five calibrated resolution bandwidths, from
300 Hz to 3 MHz (within 20%). in decade steps. Shape
factor of rile response, over the
60 dB to 6 dB amplitude
levels,
is 4:l or better.
PULLTO UNLOCK
A concentric sleeve around the VARIABLE control that
unlocks the RESOLUTION from the FREQ SPANIDIV
selector. and allows each selector to be independently
set.
LOG 10 dB/DIV
Selects a display mode with a calibrated dynamic range
of 70 dB (to the 7th graticule line from the top) at
10 dBIDIV. The bottom graticule division is not calibrated.
LOG
2 dB/DIV
When this button is depressed, the dynamic range of the
display
is acalibrated 14 dB at 2 dB/DIV.
LIN
Selects a linear display, that corresponds to the linear
calibration on the left side of the graticule overlay.
REFERENCE LEVEL, RF Attenuation, and MAXimum
Power Level Indicators and Selectors
Concentric controls that are connected in an electro-
mechanical differential arrangement which select input
altenuation and instrument gain.
The Input attenuation (from
0 dB to 60 dB) and Gain
(0 dB to 70 dB) are selected in 10 dB steps. An electro-
mechanical arrangement and readout windows establish and
indicate to the user, MAXirr~umpower input level (indBm),
RF attenuation (in dB), and the REFERENCE LEVEL (in
dBm) of the top graticule line. REFERENCE LEVEL is
also displayed on CRT's of oscilloscopes with readout
feature.
NOTE
A blue tint borders the lOdB/DIV display switch,
and four positions of the Gain selector. This
is to
correlate REFERENCE LEVEL readout to Gain
switch settings that are applicable in the 10dB/DIV
display mode. Readings outside the blue sector are
erroneous because thegain is electrically locked out.
'The CRT readout will display the < symbol to
signify the readings are erroneous. The dynamic
window of the diqlay will not exceed
--. 130dBm
(REFERENCE LEVEL of 6OdBm plus 70dB
dynamic range of the 10dB/DIV display). In the
2 dB/DIV display mode, the full 70dB range of the
Gain selector is usable. Switching the Gain fully CW
with the RF attenuator at 0 dB,produces an accurate
- 100dBm reference level. The dynamic range of the
display is now
- I14dBm (-100 dBm plus 14dB
graticule window, to the 7thgraticule line).
VARIABLE (Gain)Control
Provides at least
10 dB of gain variation. The REFER-
ENCE LEVEL readout on the CR'I' changes to the
<
symbol to indicate an uncalibrated condition when it is out
of its CAL detent. The readout of the REFERENCE
LEVEL window on the
7L12 is only applicable when this
control is in
its CALdetent.
FREQUENCY MHz
Dial reads out the START-CENTER or MARKER
frequency of the display. Frequency and dial readout are
tuned by the COARSEcontrol.
Depressing the START push-button, selects the start of
the display or left (zero)graticule line as the frequency that
is indicated by the dial readout. Depressing the CENTER
push-button selects the center of the display as the
frequency indicated in the readout window. When the
FREQ SPANIDIV is switched to MAX SPAN position, the
MARKER indicator is lighted and a notch on the baseline
of the display indicates the center of that portion of the
span that will be displayed when the FREQ SPAN
is
reduced.
FINE Frequency Controls
Two concentric controls that provide fine tuning adjust-
ment during phase lock operation or at spans which are
0.1 MHzIDiv or less.

LOG and AMP CALAdjustments
The LOG adjustment calibrates the logarithmic display
accuracy and the AMP adjustment
sets the REFERENCE
LEVELtothe top graticule line.
AUTO PHASE LOCK Switch
Used, in the phase locked modes, to disable the phase
lock. The COARSE tuning control will then tune the center
frequency without the 1st LO jumping between lock
points. This provides a wider tuning range than that of the
FINE controls.
CALOUT Connector
Provides an accurate -30 dBm, 50 MHz signal. This
signal provides an absolute reference on the display to
check dBm readings and calibrate the REFERENCE
LEVEL. Harmonics of the 50 MHz fundamental provide
picket fence markers across the frequency span for accurate
frequency and span measurements.
RF lNput Connector
A 50
Cl input connector for applying the input RF signal
to the 7L12. REFERENCE LEVEL indicator refers to the
RF level at the RF INput. Refer to General Operating
Information in regardstosignal applications.
GENERAL OPERATING INFORMATION2
This section describes how to mate the 7L12 to a
7000-SeriesOscilloscope and how to use the main features
of the instrument in making various measurements.
External graticules are designed so they will compen-
sate for parallax of the camera. Graticule markings
will therefore be correct on photographed displays.
Instructions on how to install graticule overlays, will
be found in the mainframe manual under the subtitle
light filters.
1. Preliminary Front Panel Setup and Calibration
Procedure to Match the 7L12 to
the Oscilloscope
Deflection Sensitivity
a. Plugthe 7L12 Spectrum Analyzer intothe center two
compartments, of a four plug-in 7000-SeriesOscilloscope,
or into the right two compartments, of a three plug-in
'A treatise on spectrum analyzer measurements and applications is
contained in
TEKTRONlX Measurements Concept Booklet: "Spac-
trurn Analyzer Measurement Theory and Practice:", Part No.
062-1334-00.
7000-Series Oscilloscope. Ensure that the 7L12 is securely
latched in the compartment so it cannot fall out if the
oscilloscope
is tipped forward.
b. Connect the oscilloscope mainframe to a suitable
power source and switch the POWER on. Allow about 20
to 30 minutes for instrument stabilization.
c. Set the front panel controls as illustrated in Fig. 2-2
and connect the CAL OUT signal through a short coaxial
cable tothe RF INput.
d. Adjust the oscilloscope Intensity, Focus and Astig-
matism controls for optimum display definition with
normal intensity.
e. Depress the 2 dB/DIV display mode button. Position
the baseline of the display tothe bottom graticule line with
the VERT POSition control and center the display with the
HORlZ POSitioncontrol.
f. Depress the 10 dB/DIV (LOG) display button. Dis-
play should now resemblethat shown in Fig. 2-2.
When the oscilloscopehas a
CR T with P7 phosphor, a
viewing hood will help shield ambient light and
enhance the display information.
2. Calibratethe Sweep Span
a. Switch the FREQ SPANIDIV to MAX SPAN posi-
tion, ensure that the VARIABLE (Freq Span) control
is
pushed in.
b. Position the 0 Hz response on the zero (left)graticule
line with the HORlZ POScontrol.
c. Connect the CAL OUT signal to the RF INput,
decrease the FREQSPANIDIV to 50 MHz and tune the 5th
marker (250 MHz) to the center graticule line (see Fig. 2-3).
d. Calibrate the frequency span to 50 MHzIDiv by
adjusting the SWP CAL for
1 markerldivision. It will be
necessary to keep the 250 MHz marker centered with the
COARSE FREQUENCY control as the sweep is calibrated.
-
Final display should resemble that illustrated in Fig. 2-3.

w
Top line is dBm level indi-
cated in REFERENC
LEVELwindow FOCUS: Midrange
i. .U
LI -
TIME/DIV: SPECTRUM
LOG: 10dB1DIV BOTH VIDEO FILTERS:
SwitchesOut
ATTENUATOR:
0 dB ,,,. [L**,z
I M :kxe::~l,m,
VARIABLE: IN CAL PHASE LOCK: ON
Detent
GAIN: FullyCCW RESOLUTION:
3 MHz
VARIABLE: Pushed In
are coupled together.
-30 dBm
FREQ SPANIDIV: 50MHz
CAL OUT: Connected to
RF INConnector
VIDEO PROCESSOR:
Switch Out
F
-
Fig. 2-2. 7L12 Spectrum Analyzer ina 7000-SeriesOscilloscope illustrating initial settings of front panel controls and selectors. Circled (0)
pushbuttons denote button depressed or position of selector.

I
Set 250 MHz (5th) marker at the
graticule center with HORlZ POS
Fig. 2-3. Calibratingthe sweep span.
3. Check and Adjust LOG-AMPCalibration
The LOG CAL adjustment calibrates the display so it is
logarithmic. The AMP CAL adjustment sets the reference
level to the top graticule line. There
is no interaction
betweenthese two adjustments.
a. Set the 7L12selectors and controls as directed instep
2 and tune the fundamental 50 MHz calibratorsignal tothe
center of the graticule.
b. Uncouple the RESOLUTION selector from the
FREO SPANDIV, by pulling out the PULL TO UNLOCK
sleeve, then switch the FREQ SPANIDIV to 5 MHz. The
RESOLUTION should remain
at 3 MHz. As the FREO
SPAN
is decreased, it may be necessary to re-adjust the
tuning control to keep the signal centered on screen.
c. Switch the Display Mode to 2dB1DIV and position
the baseline of the display on the bottom graticule line with
the VERT POS control.
d. Adjust the AMP CAL and the LOG CAL (if neces-
sary) to bring the 50 MHz signal within the graticule win-
dow. Adjust the AMP CAL to establish
a signal reference
amplitude of
8 divisions (Fig. 2-4 shows a full screen dis-
play
1.
e. Switch in 10dB of attenuation with the RF Atten-
uator and note the amplitude change of the signal in
- -- --
After LOG is calibrated adjust
AMP, with -30 dBm signal, so top
of graticule represents -30 dBm.
Baselineof the display must be on
the bottomgraticule line.
Fig. 2-4. Calibrating the LOG and REFERENCE LEVEL of the dis-
play (Double exposure to illustrate the two displays with reference
to each other).
graticule divisions. Amplitude change should equal 5
divisions
at 2 dB1DIV.
f. If the change
is more than 5divisions (e.g., amplitude
decreases from
8 to 2.5 div.), adjust LOG CAL to further
decrease the signal amplitude or increase the amplitude
change. Conversely if the change
is less than 5 divisions
(e.g., amplitudechanges from 8 to 3.5 div.), adjust the LOG
CAL to increase the signal amplitude. NOTE: Correct for
approximately 112 the total indicated error. This adjust-
ment may seem opposite towhat
is expected; however, the
LOG CAL adjustment shifts the reference level makingthe
net result
a correctionto the amplitude change.
g. Switch out the 10 dB of RF Attenuation. Adjust the
AMP CAL to return the signal level to the reference line.
(Ensure that the baseline of the display
is still on the
bottom graticule line.)
h. Repeat these steps until the 2dB1DIV LOG display
is
calibrated (see Fig. 2-4). Returnthe RF Attenuator to 0 dB
(REFERENCE LEVEL -30dBm), then adjust AMP CAL
to position the top of the -30 dBm signal on the reference
line. Ensure that the -30 dBm signal
is 8 divisions in
amplitude.
i. Change the display modes from 2dBlDIV to
10dBIDIV, then to LIN. Signal amplitude reference level
should not change more than 2dB from 2dBlDIV to
10dB/DIV, or 0.5 division from 2dB1DIV to LINmode.

4. Check the 10 dB/DIV and LIN Mode Display
g. Return the RF attenuator to 0 dB, the VARIABLE
Operation
Gain control to CAL. The signal amplitude should return to
full screen and the REFERENCE LEVEL should indicate
a. After completing the LOG CAL and AMP CAL -30 d~~.
adjustments, described in step 3, depress the 10 dB/DIV
button, ensure that the RF attenuator is at 0 dB and the
Gain selector is fully CCW so the REFERENCE LEVEL 5. Adjust Contrast and Check Baseline Clipper
reads -30 dBm. Operation
The contrast ratio that is set between the clipped
b. Switch the FR~~ spANIDIV to MHz and the
portion of the display baseline and the rest of the display
RESOLUTION to .3
MHz. Center the 50 MHz marker to depends on sweep rate, FREQ SPAN, RESOLUI'ION, and
the graticule center. ambient light.
c. Increase the RF attenuator setting in 10 dB steps and
note that the signal amplitude decreases 1 division each
step.
d. Switch the RF attenuator back to 10 dB, and depress
the LIN display mode button.
e. Ensure that the baseline of the display is at the
bottom graticule line, and the 50 MHz signal is centered
then adjust the VARIABLE Gain control for a signal
amplitude of 6.3 divisions.
a. With the BASELINE CLIPPER set midrange, adjust
the CONTRAST for the desired ratio between the clipped
or subdued portion and the rest of the display. (Usually the
contrast is adjusted so the clipped baseline portion is just
visible.)
b. Adjust the BASELINE CLIPPER control so the
baseline
is subdued. If there is excessive noise it may be
desirable to clip this noise level as well.
USING THE ANALYZER
1. Signal Application
f. Switch the RF attenuator to 20 dB to add 10 dB of The RF lNput impedance to the
7L12 is 50 R. At high
attenuation, and note that the signal amplitude decreases to frequencies, impedance mismatches between the RF lNput
approximately 2 divisions for a ratio change of 3.16 (this is and the signal source can cause reflections in the trans-
equivalent to 10dB in LIN mode). mission line which degrades instrument performance. Flat-
NORMAL OPERATING
RANGE
I f"--------
n
\
1 I
I l OOmV I v
I
17
-1OOdBm -90dBm -80dBm -70dBm -60dBm -50dBm -40dBm -30dBm -20dBm -1OdBm OdBm +lOdBm +20dBm
MAXIMUMSIGNAL
WITHOUT DAMAGE,
TO THE UNIT IS +30 dBm
Fig. 2-5. Volts-dBm-Wattsconversion chart for 50 R impedance.

ness, sensitivity, spurious response, etc. are all affected. To
reduce mismatch, use good quality 50
R coaxial cable to
connect the signal source to the RF lNput and keep the
cable as short as possible. Cable losses become excessive
above frequencies of
1 GHz.
Avoid applying high level signals (above -30 dBm) to
the 1st mixer of the 7L12. High level signals overload the
mixer and may produce spurious signals. A conversion chart
is shown in Fig. 2-5 to aid in determining input signal level,
in dBm, p V, and
p W, from avoltage or power source.
CAUTION
D
The maximum power input level to the RF atten-
uator is I wart average or 200 wattspeak. When the
RF input signals are riding on a DCpotential, use the
DC Block (Part No. 075-0221-OO),toprevent theDC
from reaching the 1stmixer. When the signal source is
75 R and you are using the 75 i-2 to 50 R minimum
loss attenuator, a DC block is not required because
one is incorporated in theattenuator.
, The 7L12 can be used with a75 R signal source by using
a 75
R to 50 R minimum loss attenuator. This attenuator is
available as an optional accessory (refer to the optional
accessories list in the catalog or Accessory page in the
manual for ordering information). Sensitivity and power
levels are often rated in dBm (dB with reference to 1 mW
regardless of impedance). Sensitivity and power levels for
75 fi systemsis usually rated in dBmV (dBwith reference to
1 mV across 75 a). Fig. 2-6 is a circuit diagram of a suit-
able matching pad for this purpose. The conversion from
Fig. 2-6. Circuit of a 75 a to 50 a matching pad (AC coupled).
2-10
dBmV to dBm and dBm (75 R) to dBm (50 a) through
matching attenuators
is shown in Fig. 2-7 and described as
follows:
(dBmV, into 75 R) - (dBm, at 50 i-2 end) = 54.46 dB
[I] Therefore dBmV
= 54.5 + dBm; e.g., -30 dBm (at
the
50 R input) requires (-30) + (+54.5) or t24.5 dBmV at
the 75 R input.
[21 dBm (75 R input) = dBm +5.72 (50R output);
e.g., a -30dBm input to the RF lNput of the 7L12
requires, (-30) + (+5.7) or 24.3 dBm at the 75 R input of
the pad.
[31 For some applications you may wish to know the
relationship between dBm and dBpV. For 50
R this is
dBpV = (dBm) + 107 dB.
These three relationships are shown in Fig. 2-7 for easy
graphical conversion.
Spurious response, caused by signal overload into the 1st
mixer, can be minimized if the signal amplitude is kept
within the graticule limits.
A recommendedprocedure is to
adjust the Gain selector for some baseline noise on the
display, then increase the RF Attenuator dB setting until
the strongest signals are within the graticule limits. If this
does not bring these signals within limits, add additional
external attenuators.
Fig. 2-7. Graph illustrating dBm to dBpV relationship.