TB 9-4931-538-40
m. Slowly adjust SRD BIAS on horizontal assembly A1 (fig. 11) for maximum signal
amplitude. The waveform will compress and slightly increase in amplitude. SRD BIAS
(fig. 11) must be adjusted slowly to see the slight amplitude increase.
n. Repeat l and m above until maximum signal amplitude is 0% and +100%.
o. Press Delta V key and set V MARKERS Off.
20. Frequency Adjustment
a. Set the display menu and mainframe settings to meet the following conditions:
(1) Press Display key. Display Mode to Average is highlighted. NUMBER OF
AVERAGES to # Averages = 4. Screen to Single is highlighted. Graticule to Grid is
highlighted. Bandwidth to 12.4 GHz is highlighted.
(2) Press Channels key. Channel 1 to display On is highlighted. Channel 2
through 4 display Off is highlighted. VOLTS/DIV to Sensitivity = 20 mV/div for
Channel 1 through 4. OFFSET to Offset = 0.000V. PROBE ATTEN to Chl Atten
Factor = 1.000.
(3) Press Timebase key. TIME/DIV to Sweep Speed 500 ps/div. DELAY to
Delay = 16.0000 ns. Delay Ref at Left is highlighted. Freerun/Trg'd Sweep to Trg'd
is highlighted.
(4) Press Trigger key. TRIGGER LEVEL to Trigger Level = 0.000 V. Slope
Pos to Pos is highlighted. PROBE ATTEN to Ext Atten Factor = 1.000. HF Sens to
Off is highlighted. HF Reject to Off is highlighted.
b. Connect equipment as shown in figure 5.
NOTE
If the course adjustment needs to be performed, a non-metallic
tool with a blade 0.010 inches thick and 0.040 inches wide must
be used.
d. Press Channels and OFFSET keys. Adjust TI offset to center the signal vertically.
e. Press Trigger and TRIGGER LEVEL keys. Adjust TI Trigger Level until the
positive or negative slope of the trace begins near the center horizontal graticule on the left
side of display and remains triggered.
f. Press Measure and Frequency keys. If frequency does indicate between 249.750
and 250.250 MHz, perform g and h below. If within tolerance, perform i below.
g. Remove tape from the FREQ ADJ TRIM CAP ON U9 on horizontal assembly A1 (fig. 11).
h. Re-measure the frequency while making small incremental adjustments to FREQ
ADJ TRIM CAP ON U9 (fig. 11) until frequency is 250 MHz 250 kHz (between 249.750
and 250.250 MHz) (R).