HP 8901B Operation And Calibration Manual page 73

Modulation Analyzer 1-9
Mo&/&jon
Ana'Yzer
The HP 8901B offers complete modulation analyzer capability to
meet your AM, FM and (PM measurement needs. Even difficult
measurements such as signal-to-noise and incidental AM and
FM
can be made with ease and superb accuracy using the HP 8901B.
Set up your HP 89018, Sensor Module, and signal generator as shown
in Diagram 1-1.
Adjust Your Signal Generator
RF Frequency
....................
100 MHz
Depth
...........................
.50%
Amplitude
.......................
0.0 dBm
Modulation
.................
.....AM
Rate
.............................
1
kHz
Measuring AM
1.
Press the
AM
key, the green
AUTOMATIC OPERATION
key, and the
PEAK+
detector key. The instrument should display an AM index of
approximately 50%. Notice that the instrument
is in
the Auto Tuning
mode (green AUTO TUNING LED on). The HP 8901B automatically
found and tuned to the modulated RF signal. (The Auto Tuning mode is
a good choice for making most modulation and audio measurements.)
key. The instrument is now manually tuned to the frequency of the
input signal (green LED o f f ) . (Manual Tuning is a good choice when
measuring modulation in the presence of multiple RF input signals.)
2.
Key
i n
100
M H z
by pressing the digit keys 1 0 0 and the
MHz
Selecting a Detector
The HP 8901B provides six detector functions for measuring your
modulation and audio signals.
Peak Detector
3.
Press the
PEAK-
key. Switching between the Peak+ and Peak- detector
allows you to check modulation symmetry.
4.
Press both the
PEAK+
and
PEAK-
keys at the same time. Pressing
both detector keys at the same time allows you to display the average
value of the positive and negative peak readings. (PEAK f / 2 ) .
5. Press the
PEAK+
key and then the
PEAK
HOLD
key. The Peak Hold
detector captures and holds the peak modulation level detected by the
Peak+
or
Peak- detector.
6.
Increase the modulation depth of the signal generator to
75%
and then reduce it back to
50%. Notice that the HP 8901B
continues to display the maximum modulation level. The Peak
Hold detector is ideal for detecting short modulation transients.