
Model 8640B
TM 9-4935-601-14-7&P
ADJUSTMENTS
5-42. RF OSCILLATOR END STOP ADJUSTMENT (Cont'd)
16. Recheck both stop frequencies.
17. If either the V
T
or FM Gain Compensation pots were altered, perform either the V
T
Pot (A3R1) Adjustment (5-35),
or Preliminary FM Adjustment (5-38).
5-43. RF OSCILLATOR OUTPUT POWER ADJUSTMENT
REFERENCE
Service Sheet 5.
DESCRIPTION
The RF Oscillator output will require adjusting if the power level varies beyond the 0.5 to +4.5 dBm at the
Divider/Filter Buffer Amplifier, or -12 to -2 dBm at the Frequency Counter Buffer Amplifier. The power level is adjusted
by changing the input loop penetration, of the appropriate buffer amplifier, in the oscillator cavity.
Figure 5-12. RF Oscillator Output Power Adjustment Test Setup
EQUIPMENT:
Power Meter.......................................................................................................
HP 435A
Power Sensor.....................................................................................................
HP 8481
Spectrum Analyzer . ..................................................................
HP 141T/8552B/8554B
PROCEDURE:
1 Remove A3 RF Oscillator from chassis.
2. Remove cover from the appropriate buffer amplifier assembly.
3. Re-insert A3A4 Connector Board Assembly into place while keeping oscillator section free of chassis. (It may be
necessary to unsnap the clip on the rear of the oscillator housing to free the wiring harness.
4. Connect power meter sensor to oscillator output connector A3AlJl (Divider/Filter Buffer Amplifier) or A3A1J2
(Counter Buffer Amplifier).
5. Turn LINE to ON. Tune FREQUENCY TUNE across entire band and note point of minimum power as read on
power meter. Tune to frequency of minimum power.
5-38
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