artisan 8640B - AM Sensitivity Adjustment; AM Sensitivity Adjustment Test Setup

Model 8640B TM 9-4935-601-14-7&P
ADJUSTMENTS
5-31. OUTPUT LEVEL VERNIER AND METER ADJUSTMENT (Cont'd)
11. Set generator's OUTPUT LEVEL switch to --97 dBm. Set analyzer's reference level control to -60 dBm. Adjust
OUTPUT LEVEL vernier to set signal on analyzer's display to the fifth horizontal graticule line (to the same place
it was set in step 6). Adjust the 1 V adjustment, A1A1R6, for a -97 dBm indication on generator's panel meter
(+3 dB reading on meter).
12. Perform AM Sensitivity Adjustment, paragraph 5-32, if repairs have been made to the A26 AM/AGC and RF
Amplifier Assembly.
5-32. AM SENSITIVITY ADJUSTMENT
REFERENCE:
Service Sheet 14.
DESCRIPTION:
AM sensitivity is adjusted while comparing the actual amount of amplitude modulation to the level of the input modulating
signal. A spectrum analyzer is used to measure the actual modulation. The analyzer is used with zero frequency span at
the carrier frequency. A DVM is used to measure the ac and dc voltages at the analyzer's vertical output, and the dc
value of the carrier is set to 282.8 mVdc; the rms value of the modulation is then a very accurate measure of AM percent
(% AM is 1/2 the ac voltage in mVrms).
EQUIPMENT:
Spectrum Analyzer...........................................................HP 141T/8552B/8554B
Digital Voltmeter .......................................................................HP 3480B/3484A
Test Oscillator........................................................................................HP 652A
Calibrated Step Attenuator.....................................................HP 355D OPT H36
Figure 5-2. AM Sensitivity Adjustment Test Setup
5-17
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