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Chapter 1 17
Making Basic Measurements
Resolving Signals of Equal Amplitude
5. Decrease the video bandwidth to 10 kHz, by pressing Video BW, 10,
kHz. Two signals are now visible as shown in Figure 1-7. Use the
front-panel knob or step keys to further reduce the resolution
bandwidth and better resolve the signals.
Figure 1-7 Resolving Signals of Equal Amplitude After Reducing the Video
Bandwidth
As the resolution bandwidth is decreased, resolution of the individual
signals is improved and the sweep time is increased. For fastest
measurement times, use the widest possible resolution bandwidth.
Under factory preset conditions, the resolution bandwidth is “coupled”
(or linked) to the center frequency.
Since the resolution bandwidth has been changed from the coupled
value, a # mark appears next to Res BW in the lower-left corner of the
screen, indicating that the resolution bandwidth is uncoupled. (For
more information on coupling, refer to the Auto Couple key description
in the Agilent Technologies EMC Analyzers User’s Guide.)
NOTE To resolve two signals of equal amplitude with a frequency separation of
200 kHz, the resolution bandwidth must be less than the signal
separation, and resolution of 100 kHz must be used. The next larger
filter, 300 kHz, would exceed the 200 kHz separation and would not
resolve the signals.