User`s guide

Demodulating and Listening to an AM or FM Signal
Note
This application should only be performed using an HP 85913, HP 8593E,
HP 85943, HP 85953, or HP 85963 with Option 102 or 103.
The functions listed in the menu under Demod allow you to demodulate and hear signal
information displayed on the spectrum analyzer. Simply place a marker on a signal of interest,
activate AM or FM demodulation, and then listen.
Example:
1. Connect an antenna to the spectrum analyzer input.
2. Select a frequency range on the spectrum analyzer, such as the range for FM radio
broadcasts. For example, the frequency range for FM broadcasts in the United States is
88 MHz to 108 MHz. Press c-1, (m), START FREQ , 88 [MHz_), STOP FREQ ,
108 INIHz).
3. Place a marker on the signal of interest by using PEAK SEARCH) to place a marker on the
highest-amplitude signal, or by pressing [MKR) ,
MARKER NORMAL and moving the marker to a
signal of interest.
4. Press [AUXCTRL_), Demod, DEMOD ON OFF (so that ON is underlined), and DEMOD AM FM
(so that FM is underlined). SPEAKER ON OFF is set to ON by the preset function. Use the
front-panel volume control to control the speaker’s volume.
4
REF 0 dBm
FM”
LOG
10
dE/
MKR
104.90 MHZ
BTTEN
10 dB
-46 61 dEm
START 88 00 MHz
STOP
100.00 MHZ
RES BW
100 kHz
“BW 30 kHr
SWP 75 msec
Figure 4- 11. Demodulation of an FM Signal
5. The signal is demodulated at the marker’s position for the duration of the dwell time. llse
the step keys, knob, or number/units keypad to change the dwell time. For example, press
the step-up key (m) twice to increase the dwell time to 2 seconds.
6. The peak search functions can be used to move the marker to other signals of interest.
PIY?SS [PEAK SEARCH] t.0 XCeSS NEXT PEAK , NEXT PK RIGHT , OI- NEXT PK LEFT .
Making Measurements 4-13