
Model 8640B
TM 9-4935-601-14-7&P
ADJUSTMENTS
5-36. VT VOLTAGE ADJUSTMENT (Cont'd)
2. Set FREQUENCY TUNE to 356 MHz approached from low frequency band end (256 MHz); adjust VT
adjustment, A3A4R2 until the relays in the A10 assembly just actuate. When the relays actuate, they make an
audible clicking.
3. Tune FREQUENCY TUNE one turn ccw and then cw until relays actuate. The frequency at actuation should be
355 - 357 MHz.
4. Tune FREQUENCY TUNE from 256 to 512 MHz. The generator's panel meter should read 0 dBm through the
entire frequency range.
5-37. RF FILTER ADJUSTMENT
RE VERENCE:
Service Sheet 10.
DESCRIPTION:
A spectrum analyzer and a tracking generator are used to measure the insertion loss and frequency response of each of
the RF filters. Those filters that are adjustable are adjusted if necessary. A frequency counter, connected to the tracking
generator's auxiliary output, is used to accurately set the analyzer's frequency. This procedure should be performed
whenever the RF filters have been repaired or are suspect. The filters must meet specified pass band and stop band
characteristics. Figure 5-4 illustrates the terms used in the procedure.
Figure 5-4. Filter Terminology
5-23
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