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66 Chapter 1
Making Basic Measurements
Demodulating FM Signals
4. Set the span to 1 MHz by pressing SPAN, Span, 1, MHz.
5. Set the Y-Axis Units to dBm by pressing AMPLITUDE, More,
Y-Axis Units,
dBm.
6. Set the reference level to –20 dBm by pressing AMPLITUDE, Ref Level,
–20, dBm.
7. Set the resolution bandwidth to 100 kHz by pressing BW/Avg,
Res BW, 100, kHz. The skirt is reasonably linear starting
approximately 5 dB below the peak.
8. Select a marker by pressing Marker, then move the marker
approximately 1/2 division down the right of the peak (high
frequency) using the front-panel knob.
9. Place a delta marker 150 kHz from the first marker by pressing
Delta, 150, kHz. The skirt looks reasonably linear between markers.
10.Determine the offset from the signal peak to the desired point on the
filter skirt by moving the delta marker to the midpoint. Press 75, kHz
to move the delta marker to the midpoint. See Figure 1-56.
Figure 1-56 Establishing the Offset Point
11. Press Delta to make the active marker the reference marker.
12.Press Peak Search to move the delta marker to the peak. The delta
value is the desired offset, for example 151 kHz. See Figure 1-57.