Chapter 7 Transmission Operation
Selecting RBW, VBW and SWT
122 9102 Handheld Spectrum Analyzer Software version 5.31
Selecting RBW, VBW and SWT
The resolution bandwidth (RBW) is the 3 dB bandwidth of the IF filter
for selecting the signal to be measured. The resolution bandwidth
describes the ability of the spectrum analyzer to discriminate between
adjacent signals of similar amplitude. Only signals spaced at a
frequency of more than the RBW can be discriminated from one
another.
The 9102 can be set to automatically select the resolution bandwidth,
depending on the frequency span.
The video bandwidth (VBW) is the lowpass filter over which several
results for one frequency point are smoothened. The lower the video
bandwidth, the smoother the signal curve and the less variations there
are.
The 9102 can be set to select the video bandwidth automatically as a
function of the resolution bandwidth. A typical value for the video band-
width should be equal or 10 times lower than the radio bandwidth
value.
The sweep time (SWT) determines how long it takes for a complete
sweep over the measured frequency range (span).
The 9102 can be set to automatically select the sweep time, depending
on RBW and VBW. If manually set, the sweep time should be selected
long enough for the filtered signal to reach steady state. The 9102 will
output an “UNCALibrated” warning if the sweep time is too low.
To set the resolution bandwidth, the video bandwidth or the sweep
time, proceed as follows:
1 In the main menu, select the appropriate softkey (
RBW, VBW, or
SWT).
2 Enter the value and complete the entry with the appropriate enter
key for the unit, select a new value with the help of the U
P/DOWN
cursor keys, or switch to
auto to leave the setting to the 9102.
Changing between automatic and manual mode
Push the appropriate softkey (
RBW, VBW, or SWT) until the desired
selection (auto or manual) is highlighted.
Setting up the level parameters
The dynamic range between the measured signal and the noise floor
depend on the proper setting of the level settings. These consist of the
reference level and the attenuation.
The reference level basically determines the level at the top of the
display. The vertical axis is divided into eight horizontal rows. You can
adjust the scale (which defaults to 10 dB per line) to your preferences.
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