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90 Chapter 2
Making Complex Measurements
Demodulating and Listening to an AM Signal
11.Press Det/Demod, Detector, Sample to set the detector mode of the
analyzer to Sample.
12.Press
Det/Demod, Demod, AM. Use the front panel volume knob to
control the speaker volume.
13.You can turn your analyzer into a % AM indicator as follows:
a. Set trigger to free run by pressing Trig, Free Run.
b. Set the sweep time to 5 seconds by pressing
Sweep,
Sweep Time,5,s.
c. Set the video filter to 30 Hz by pressing
BW/Avg, Video BW, 30, Hz.
d. Change the reference level to position the trace at midscreen by
pressing
AMPLITUDE, Ref Level, and adjust the reference level
using the front-panel knob.
e. Reset the video filter to a high value. For example, press
BW/Avg,
Video BW, 30, kHz.
f. Set the sweep time to 5 milliseconds by pressing
Sweep, Sweep
Time
, 5, ms.
The center horizontal line of the graticule now represents 0% AM;
the top and bottom lines, 100% AM. See Figure 2-17.
14.The signal to the speaker will be interrupted during retrace because
the analyzer is performing automatic alignment routines. To
eliminate the interruption and clicks between sweeps, turn the auto
alignment function off by pressing
System, Alignments, Auto Align,
Off.
NOTE Refer to the specifications for information about operating the analyzer
with the alignments turned off.