
Model 8640B
TM 9-4935-601-14-7&P
PERFORMANCE TESTS
4-33. AM DISTORTION TEST (Cont'd)
MODULATION FREQUENCY ................................................................. 1000 Hz
FM ................................................................................................................OFF
RANGE ......................................................................................... 256 - 512 MHz
FREQUENCY TUNE .............................................................................. 512 MHz
OUTPUT LEVEL ........................................................... -17 dBm (Vernier full cw)
RF ON/OFF ....................................................................................................ON
2. Set spectrum analyzer's resolution bandwidth to 300 kHz, input attenuation to 20 dB, frequency span per division
(scan width) to 10 MHz, scale to linear, and adjust center frequency and scale reference level controls to center
the 512 MHz signal on the display. Set frequency span per division to 0 Hz and display smoothing (video filter)
to 10 kHz. Peak trace on display with center frequency controls; set trace to the center of display with reference
level controls.
3. Set generator's AM switch to INT and adjust MODULATION control for 50% modulation as read on generator's
panel meter.
4. Calibrate the distortion analyzer for 1 kHz. Measure and record distortion; it should be less than 1% with trace
peaked on analyzer display.
________________1%
5. Use generator's MODULATION control to set AM percent to 70% and 90%; calibrate the distortion analyzer and
measure distortion at each modulation depth. Distortion should be less than 3% with trace peaked on analyzer
display.
70% AM:___________3%
90% AM:___________3%
6. Increase generator's RF OUTPUT LEVEL one step cw and reduce the vernier to give -17 dBm. Repeat steps 3
to 5.
4-34. AM SENSITIVITY AND ACCURACY TEST
SPECIFICATION:
External AM Sensitivity: (400 Hz and 1 kHz rates)
(0.1 ± 0.005)% AM per mV peak into 600
Ω
with AM vernier at full CW position.
Indicated AM Accuracy: (400 Hz and 1 kHz rates using internal meter)
±8% of reading on 0 - 10 scale
±9% of reading on 0 - 3 scale (for greater than 10% of full scale).
4-50
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