HP 8901B Operation And Calibration Manual page 123

Modulation and Audio
5-7
S/NAD
The HP 8901B allows you to make SINAD measurements (at 1 kHz or
400
Hz)
on the internally demodulated audio signal or on an external audio
signal applied to the MODULATION OUTPUT/AUDIO INPUT port.
Demodulated Audio
1. Connect your modulated signal source to the HP 8901B's INPUT port.
2.
Select the appropriate modulation mode (AM,
FM
or @M).
3.
Key in 29.0
SPCL,
the Blue Shift key, and then the
1 kHr
DlSTN (PEAK+)
or 400
Hs
DISTN
(PEAK-) key. An annunciator
in the display indicates which frequency is being measured.
4.
Use the
LOG/LIN
key if you wish to toggle between
%
and dB units.
5.
Press the appropriate Audio Filter keys to set the desired
measurement bandwidth for the internally demodulated audio signal.
External Audio
INPUT port on the
HP
8901B.
6.
Connect your audio source to the MODULATION OUTPUT/AUDIO
7.
Press the
AUDIO INPUT
key (key should remain lit).
8.
Perform steps 3 and
4
above to measure the SINAD of the external
audio signal.
Signal-fo-Noise
The HP 8901B's Ratio Mode makes it easy to make relative measurements
such as signal-to-noise on
AM
transmitters or hum and noise on
FM transmitters.
the modulation
o f f .
or
FM)
and the
R M S
detector.
reference measurement.
1 . Connect your signal source to the INPUT port on the
HP
8901B and
turn
2.
Select the appropriate modulation measurement on the HP 8901B, (AM,
3.
Press the
RATIO
key to establish the unmodulated input signal as the
4.
Press the
LOG/LIN
key if you wish to toggle between
%
and dB units.
5.
Turn on the modulation at the modulation source. The HP 8901B will
compute and display the signal-to-noise ratio.