Model 8901B Operation
@M
FUNCTIONS
OM, Special finction
2
(Audio Range)
DESCRIPTION
The @M key enables the Modulation Analyzer
to
measure the phase deviation of the tuned input signal.
The demodulated OM is present at MODULATION OUTPUT/AUDIO INPUT.
The OM measurement is specified only for
RF
carriers
from
10
to
1300
MHz; however,
OM
measurements can be performed on carriers from
150
kHz
to
10
MHz.
The @M measurement is only specified for modulation rates from 200 Hz
to
20
kHz;
however, the low
frequency
3
dB
limit
is
typically
7
Hz.
The following figure shows the display resolution for different combinations of peak phase deviation
and modulation
rate.
RESOLUTION
0.001
RADIAN
RESOLUTION
200
Hz
500
Hz
1
kHz
2
kHz
5
kHz
10
kHz
20
kHz
MODULATION RATE
PROCEDURE
To make a
OM
measurement, first tune the instrument
to
the input signal by selecting AUTOMATIC
OPERATION. Select OM.
Select an audio detector: PEAK+, PEAK-, PEAK
*
/2,
AVG, or RMS. (The RMS detector, selected
by pressing the Blue Key and the
RMS
key, is less accurate in measuring OM and
is
typically only
used
for
audio distortion measurements.)
OM
3-169
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