HP 8901B Operation And Calibration Manual page 413

Adjustments Model
8901B
6. On the Modulation Analyzer, press OM. Adjust A3R27
(OM
SENS)
for a display of the same
numerical value as the display in
kHz
of step 5 f0.2 rad.
NOTE
If
a test oscillator
is
used in place of the audio synthesizer, the modulation
rate must be measured with a counter (or simply key in S (Shift) AUDIO
FREQ).
The
adjustment
is
then made to give a display e q d to the ratio
(frequency deviation)/(modulation rate).
5-22 Adjustment 13