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38 Chapter 1
Making Basic Measurements
Measuring Low Level Signals
3. On the analyzer, perform a factory preset by pressing Preset,
Factory Preset (if present).
4. Set the center frequency of the analyzer to 300 MHz by pressing
FREQUENCY, Center Freq, 300, MHz.
5. Set the span to 5 MHz by pressing SPAN, Span, 5, MHz.
6. Set the resolution bandwidth to spectrum analyzer coupling by
pressing
BW/Avg, Res BW (SA).
7. Set the Y-Axis Units to dBm by pressing AMPLITUDE, More,
Y-Axis Units,
dBm.
8. Set the reference level to −40 dBm by pressing AMPLITUDE, Ref Level,
–40,
dBm.
9. Place the signal at center frequency by pressing Peak Search,
Marker→, Mkr→CF. See Figure 1-30.
Figure 1-30 30 kHz Video Bandwidth
10.Narrow the video bandwidth by pressing BW/Avg, Video BW, and the
step-down key (↓). This clarifies the signal by smoothing the noise,
which allows better measurement of the signal amplitude.
A # mark appears next to the VBW annotation at the bottom of the
screen, indicating that the video bandwidth is not coupled to the
resolution bandwidth. See Figure 1-31. As the video bandwidth is
reduced, the sweep time is increased to maintain calibrated data.
Instrument preset conditions couple the video bandwidth to the
resolution bandwidth. If the bandwidths are uncoupled when video
bandwidth is the active function, pressing
Video BW (so that Auto is
underlined) recouples the bandwidths.