HP 8901B Operation And Calibration Manual page 74

1-1 0 Modulation Analyzer
150 kHz to 9.999$99 MHz
10 MHz
to
1300 MHz
Average Detector
7.
Now press the
AVG
key to select the average-responding detector.
You
have selected an average responding detector that is calibrated to
read the r m s value of a sinewave. The HP 8901B should be displaying
approximately 35%
AM
with the signal generator set at 50% AM.
20 Hz to 10 kHz
99%
20 Hz to 100 kHz
RMS Detector
8.
Press the
Blue
Shift
key and then the
RMS (AVG)
key (the red
LED
below the
RMS
key will come on). You have now selected a true-RMS
detector. The Average detector and the RMS detector are good choices
when measuring noise or residual modulation where the nns value is
generally more desirable than the peak value. The true-RMS detector
can be used to measure modulation rates up to 40 kHz and provides
one more digit of resolution than the Average Detector. The true-RMS
detector is also a good choice for measuring non-sinusoidal signals.
AM Measurement
Ranges
Simply select AM and any of the above detector functions to make AM
measurements within the following ranges:
I
Max- Depth
1
RF
Carrier Frequency
I
Modulation Rate
Measuring FM
1.
Turn off AM on the signal generator and
turn on
25
kHz of
FM
deviation at a
1
kHz rate.
2.
Press the
FM
key, the green
AUTOMATIC OPERATION
key, and the
PEAK+
detector key. The HP 89018 should display a reading of about
25 kHz. Notice that in the upper right comer of the instrument the
yellow FM MODULATION OUTPUT LED is lit. This indicates that the
demodulated FM signal is available at the front-panel MODULATION
OUTPUT/AUDIO INPUT port. (Connecting another audio analyzer
to this port will enable you to make audio measurements on the
demodulated signal while monitoring modulation with the HP 89018.)