HP Cable Box 8591C manual Making Basic Measurements Using Spectrum Analyzer Mode

Making Basic Measurements Using Spectrum Analyzer Mode

Measuring low-level Signals Using Attenuation, Video Bandwidth, and Video Averaging

Example: If a signal level is very close to the noise floor, video averaging is another way to make the signal more visible.

N O T E

The time required to construct a full trace that is averaged to the desired degree is approximately the same when using either the video-bandwidth or the video-averaging technique. The video bandwidth technique completes the averaging as a slow sweep is taken, whereas the video averaging technique takes many sweeps to complete the average. Characteristics of the signal being measured such as drift and duty cycle determine which technique is appropriate.

Video averaging is a digital process in which each trace point is averaged with the previous trace-point average. Selecting video averaging changes the detection mode from peak to sample. The result is a sudden drop in the displayed noise level. The sample mode displays the instantaneous value of the signal at the end of the time or frequency interval represented by each display point, rather than the value of the peak during the interval. Sample mode is not used to measure signal amplitudes accurately because it may not find the true peak of the signal.

Video averaging clariEes low-level signals in wide bandwidths by averaging the signal and the noise. As the spectrum analyzer takes sweeps, you can watch video averaging smooth the trace.

1.Position a low-level signal on the spectrum analyzer screen.

2.Press (-1, More 1 of 3 , then VID AVG OM OFF . When ON is underlined, the video-averaging routine is initiated. As the averaging routine smooths the trace, low-level signals become more visible. VID AVG 100 appears in the active function block.

The number represents the number of samples (or sweeps) taken to complete the averaging routine.

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