Chapter 2 89
Making Complex Measurements
Demodulating and Listening to an AM Signal
7. The signal is demodulated at the marker position on ly for t h e
duration of the demod time. Use the step keys, knob, or numeric
keypad to change the dwell time. For example, press the step up key
(↑) to increase the dwell time to 2 seconds.
8. The marker search functions can be used to move the marker to
other signals of interest. Press Peak Search to access Next Peak,
Next Pk Right, or Next Pk Left.
Demodulating and Listening to an AM Signal Example 2:
1. Connect an antenna to the analyzer input.
2. Perform a factory preset by pressing Preset, Factory Preset (if
present).
3. Select a frequency range on the analyzer, such as the range for AM
radio broadcasts. For example, the frequency range for AM
broadcasts in the United States is 55 0 kH z t o 165 0 kHz. Press
FREQUENCY, Start Freq, 550, kHz, Stop Freq, 1650, kHz.
4. Place a marker on the signal of interest. Press Peak Search to place a
marker on the highest amplitude signal, or press Marker, Normal and
move the marker to a signal of interest.
5. Set the resolution bandwidth to spectrum analyzer by pressing
BW/Avg and Res BW (SA).
6. Set the frequency of the signal to center frequency by pressing
FREQUENCY then Signal Track (On) if the signal of interest is the
highest amplitude on screen signal. If it is not the highest amplitude
signal on screen, move the signal to center screen by pressing
Peak Search, Marker→, and Mkr→CF.
7. If the signal track function is on, press SPAN, 1, MHz to reduce the
span to 1 MHz. If signal track is not used, use the step down key (↓)
to reduce the span and use Mkr→CF to keep the signal of interest at
center screen.
8. Set the span to ze ro by pressing SP AN, Zero Span. Zero Span turns off
the signal track function.
9. Change the resolution bandwidth to 100 kHz by pressing BW/Avg,
Res BW, then enter 100, kHz.
10.Set the signal in the top two divisions of the screen by changing the
reference level. Press AMPLITUDE, and then the step down key (↓)
until the signal is in the top two divisions. Set the amplitude scale to
linear by pressing Scale Type (Lin). Keep the signal center displayed
by pressing AMPLITUDE, Ref Level and using the (↑) (↓) step keys.