User`s guide

Example: If a signal level is very close to the noise floor, video averaging is another way to
make the signal more visible.
Note
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 clarifies 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 (j%ZEJ More 1 of 3, then VID AVG ON OFF . When ON is underlined, the
video-averaging routine is initiated. As the averaging routine smoothes 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.
3. To set the number of samples, use the number/units keypad. For example, press
VID AVG ON OFF (so that ON is underlined), 25 IHz). Turn video averaging off and on again
by pressing VID AVG ON OFF (OFF), VID AVG ON OFF (ON).
The number of samples equals the number of sweeps in the averaging routine.
During averaging, the current sample appears at the left side of the graticule. Changes in
active functions settings, such as the center frequency or reference level, will restart the
sampling. The sampling will also restart if video averaging is turned off and then on again.
Once the set number of sweeps has been completed, the spectrum analyzer continues to
provide a running average based on this set number.
3-l 8
Making Basic Measurements