HP 8901B Operation And Calibration Manual page 170

Operation Model 8901B
Approximate
FM Modulation Rate
FM Frequency Limits (Hz)
Time Constant
Minimum Maximum
3 1 83 3088
2 1 22 75 2058 2 1 87
2 1 2 750 205.8 2 1 8 . 7
Approximate
FM Modulation Rate
(Hz)
50
300
Audio Frequency and Audio Filters Check
28. Set FM DE-EMPHASIS and PRE-DISPLAY off. Set the FM rate as listed in the following table.
For each setting, perform the following steps:
a. Set the HP FILTER and LP FILTER to ALL OFF.
b. Set the signal generator's FM rate as listed in the table.
c. Press the FM key then press the RATIO key to establish a reference of 0
dB.
d. Set the H P or LP FILTER as listed in the table, and fine adjust the FM rate for a reading
e. Press the S (Shift) key then the AUDIO FREQ key and note the FM rate. The Modulation
of -3.0
d B
REL.
Analyzer should display a rate within the limits listed.
Frequency Limits (Hz)
Minimum Maximum
HP or LP Filter
50
Hz
HP
47.5 52.5
300 Hz
HP
285 3 1 5
3
000
15 000
90 000
3
kHz
LP
2 850 3 150
15 kHz
LP
1
14250
1
15750
>20 kHz LP 80
000
140 750
Audio Distortion and SINAD Check
29. Press the AM key and set the LP FILTER to ALL OFF. Set the signal generator's FM off, and
set the AM depth to 50% (as measured on the Modulation Analyzer's display) at a
1
kHz rate.
Press the
S
(Shift) key then the AUDIO DISTN key (the FM key). The displayed distortion
should be less than 3%. (The display should also indicate 1 kHz. If 400 Hz is displayed, press the
Blue key then the 400 Hz DISTN key (the PEAK- key).)
30. Set the signal generator's AM for a 400
H z
rate. Press the Blue key then the 400 Hz DISTN key
(the PEAK- key). The displayed distortion should be less than 3%.
31. Press the LOG/LIN key to display the distortion in
dB.
Key in 29.0 and press the SPCL key.
The displayed SINAD should be greater than 30 dEL
External Audio RMS Level Check
32. Connect the audio (AM
or
trigger) output of the signal generator to the input of the
oscilloscope. (See Figure 3-10.) Set the signal generator's audio output level for 3 Vpp as read on
the oscilloscope.
33. Connect the audio output of the signal generator to the MODULATION OUTPUT/AUDIO
INPUT of the Modulation Analyzer. (See step 33 of Figure 3-10.) Key in 30.0 and press the
SPCL key. If the display is in
dl3
V, press the LOG/LIN key to display V. The Modulation
Analyzer's displayed level should be between 0.95 and
1.17V.
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