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:

•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.

•Linear mode should be used in amplitude modulation (AM) measurements to avoid distortion caused by the logarithmic amplifier when demodulating signals.

•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.

•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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