ADInstruments AD8000 Series Instruction Manual page 68

AD8000 Series Spectrum Analyzer Instruction
Manual
(2) VBW
Video bandwidth (VBW) is very useful to detect the signal in the noise. It is
the lower pass filter after the IF filter which is used to average (smooth) the
noise. This process could make the s/n increases about 10dB. To improve
the filter's effect, users should manually set the VBW as 1/10 or smaller of
the RBW. When VBW is set to 'Auto', the VBW will change and equals to
RBW. The decreasing of VBW would increase the sweep time. Two figures
below show the influence of different VBW towards the wave.
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Fig. 3-26 Large VBW
Fig. 3-27 Small VBW