Smoothing Effect of VBW-to-RBW Different Ratios

The effect is most noticeable in measuring noise, particularly when a wide
resolution bandwidth is used. As we reduce the video bandwidth, the peak-
to-peak variations of the noise are reduced. As Figure 2-29 shows, the degree
of reduction (degree of averaging or smoothing) is a function of the ratio of
the video to resolution bandwidths. At ratios of 0.01 or less, the smoothing
is very good. At higher ratios, the smoothing is not so good. The video filter
does not affect any part of the trace that is already smooth (for example,
a sinusoid displayed well out of the noise) .

Figure 2-29. Smoothing effect of VBW-to-RBW ratios of 3: 1, 1: 10, and 1: 100