HP 8901B Operation And Calibration Manual page 169

Model 8901B Operation
HP 8901B
MODULATION ANALYZER
0
0
RF OUTPUT
SIGNAL GENERATOR
oaooo
ooooo 0 0 ~ 0 ~ 0 SENSOR
SENSOR MODULE
0 0
DODO
@
0
0 0
oooaoo a
DODO
*
5 0 OHM
Figure 3-9. AM Check Setup
FM
and Phase Modulation
(OM) Checks
23. Set the signal generator's AM off and set FM to 50 kHz peak deviation (as measured on its FM
meter) at a 1 kHz rate. Press the FM key. The Modulation Analyzer should display between 45.0
and 55.0 kHz.
24. Adjust the signal generator's FM peak deviation for 50 kHz as displayed by the Modulation
25. Press the OM key. The instrument should display between 45.0 and 55.0 rad.
Analyzer.
FM
De-emphasis Check
26. Press the FM key. Press the RATIO key. If the display is in
dB,
press the LOG/LIN key to display
5%.
The instrument should display between 99.8 and 100.2% REL. The oscilloscope should show
a sinusoidal waveform with a peak-to-peak amplitude between 0.9 and 1.1V and a period of 1 ms.
27. Press the LOG/LIN key. Press the RATIO key. Press the PRE-DISPLAY key. Set the FM rate
as listed in the following table. For each setting, perform the following steps:
a. Set the FM DE-EMPHASIS off if it is on. (Leave PRE-DISPLAY on.)
b. Set the signal generator's FM modulation rate to a value approximate to that listed in
c. Press the RATIO key to establish a reference of 0 dl3.
d. Press the FM DE-EMPHASIS time constant key listed in the table.
e. Adjust the modulation rate (but not the level) until the displayed modulation is -3.0
dB.
f. Press the
S
(Shift) key then press the AUDIO FREQ key (the AM key). The Modulation
Analyzer should display a rate within the limits listed. Also, the oscilloscope waveform should
change proportionately with the display. (Allow for a times 10 amplitude a t the output of
MODULATION OUTPUT/AUDIO INPUT when FM DE-EMPHASIS
is
set to 750
ps.)
the table.
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