Tektronix 1L20, Instruction Manual

Page: 39 / 117

Performance Check— Type 1L20
g. Adjust the G A IN control of the Analyzer for 6 centi­
meters of signal deflection.
h. Add 26 dB of IF ATTEN. (Set the 20 dB; 4 dB, and 2 dB
switches to On.)
i. Check that the signal is just discernible.
j. Set the VERTICAL DISPLAY switch to SQ LAW and
return all IF ATTEN switches to OFF.
k. Adjust the G A IN control o f the Analyzer fo r 6 centi­
meters o f display.
l
. Add 13 dB of IF ATTEN. (Set the 8dB, 4dB , and 1 dB
switches to On.)
m. Check that the signal is just discernible.
14. TO RECORDER Output Check
a. Preset the controls of the Spectrum Analyzer as follows:
POS
DISPERSION RANGE
DISPERSION-
COUPLED RESOLUTION
VIDEO FILTER
VERTICAL DISPLAY
INT 1 MHz REF FREQ
b. Connect the 1 MHz C
INPUT connector.
Position the trace to the
bottom line of the
graticule.
M H z/C M
1
O ff (Down)
LIN
Up
MARKERS OUT to the RF
c. Adjust the G AIN control for a 6 centimeter display.
(Readjust the POS control if necessary to position the trace
to the bottom line of the graticule.)
d. Measure the TO RECORDER signal with the test oscillo­
scope. Check for 12 millivolts to 20 millivolts.
e. Disconect the test oscilloscope.
G A IN Full clockwise
VERTICAL DISPLAY VIDEO
c. Apply a 50 kHz signal from an audio generator to the
VIDEO INPUT connector o f the Analyzer. Adjust the Output
control of the generator to obtain 4 centimeters o f deflection.
d. Monitor the signal amplitude with a DC coupled test
oscilloscope for constant amplitude, and decrease the output
frequency of the generator.
e. Check the frequency a t which the Analyzer display
falls to 2.8 centimeters. This frequency should be < 1 6 Hz.
f. A pply a 50 kHz signal from the Constant Amplitude
RF Generator to the VIDEO INPUT connector of the Analyzer.
Adjust the signal amplitude for 4 centimeters of deflection.
g. Increase the signal frequency until the amplitude of the
Analyzer display falls to 2.8 centimeters. At this point the
output frequency should be > 1 0 MHz.
17. Incidental Frequency Modulation Check
a. Insert the Analyzer directly into the oscilloscope plug-in
compartment. (Do not use the extension.)
b. Preset the Spectrum Analyzer controls as follows:
DISPERSION RANGE kHz/CM
DISPERSION 500
IF ATTEN All OFF
c. Apply a 200 MHz signal from the Time-Mark Generator
to the BAND 1 RF INPUT connector and center the IF feed
through signal on the CRT.
d. Change the DISPERSION— COUPLED RESOLUTION
switch to 1, adjusting the IF CENTER FREQ controls to keep
the signal centered on the screen.
e. Adjust the G A IN control for six centimeters o f deflec­
tion.
f. Adjust the POS control fo r a display similar to Fig. 5-6.
15. VIDEO FILTER Check
a. Set up the Analyzer as directed in Step 5-14a, b, c
above.
b. Switch on the VIDEO FILTER and check for an atten­
uated display resembling a sawtooth.
c. Change the sweep rate to 1 sec/cm. The display should
be the same in either position of the VIDEO FILTER switch.
16. VIDEO INPUT Frequency Response Check
a. Insert the Analyzer directly into the oscilloscope plug-in
compartment. (Do not use the extension.)
b. Preset the controls of the Spectrum Analyzer as follows:
POS Position the trace to the
center line of the
graticule.
Fig. 5-6 . Typical display for Incidential Frequency-Modulation Check
(Step 1 7 ).
5 -7