Decreasing Video Bandwidth - HP 8590 E-Series User Manual

A "#I' mark appears next to the
indicating that the resolution bandwidth is uncoupled.
As the resolution bandwidth is reduced, the sweep time is increased to maintain calibrated
data.
Example: The video-filter control is useful for noise measurements and observation of
low-level signals close to the noise floor. The video filter is a post-detection low-pass filter that
smoothes the displayed trace. When signal responses near the noise level of the spectrum
analyzer are visually masked by the noise, the video filter can be narrowed to smooth this noise
and improve the visibility of the signal. (Reducing video bandwidths requires slower sweep
times to keep the spectrum analyzer calibrated.)
Using the video bandwidth function, measure the amplitude of a low-level signal.
1. As in the first example, connect an antenna to the spectrum analyzer input. Set the
spectrum analyzer to view a low-level signal.
the signal amplitude.
A "#" mark appears next to the VBW annotation at the bottom of the screen, indicating that
the video bandwidth is not coupled to the resolution bandwidth.
Instrument preset conditions couple the video bandwidth to the resolution bandwidth
so that the video bandwidth is equal to or narrower than the resolution bandwidth. If
the bandwidths are uncoupled when video bandwidth is the active function, pressing
VID BW AUTO MAN
Note
The video bandwidth must be set wider than the resolution bandwidth when
measuring impulse noise levels.
RES BW
annotation at the lower-left corner of the screen,
(so that AUTO is underlined) recouples the bandwidths. See Figure 3-19.
Figure 3-19. Decreasing Video Bandwidth
Making Basic Measurements 3-17