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Using
the
Analyzer
As
a
Receiver
in
Zero
Frequency
Span
The spectrum analyzer operates as a fixed-tuned receiver in zero span. The
zero span mode can be used to recover modulation on a carrier signal
Center frequency in the swept-tuned mode becomes the tuned frequency
in zero span. The horizontal axis of the screen becomes calibrated in time,
rather than frequency. Markers display amplitude and time values.
The following functions establish a clear display of the video waveform:
l Trigger stabilizes the waveform trace on the display by triggering on the
modulation envelope. If the signal’s modulation is stable, video trigger
synchronizes the sweep with the demodulated waveform.
l Linear mode should be used in amplitude modulation (AM) measurements
to avoid distortion caused by the logarithmic amplifier when demodulating
signals.
l Sweep time adjusts the full sweep time from 20 ms (20 ps in zero span),
to 100 s. The sweep time readout refers to the full lo-division graticule.
Divide this value by 10 to determine sweep time per division.
l Resolution and video bandwidth are selected according to the signal
bandwidth.
Each of the coupled function values remains at its current value when zero
span is activated. Video bandwidth is coupled to resolution bandwidth.
Sweep time is not coupled to any other function.
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