Common Measurement Settings
R&S
®
FSVA3000/ R&S
®
FSV3000
378
User Manual 1178.8520.02 ─ 01
The level of a sine wave signal is not influenced by the video bandwidth. A sine wave
signal can therefore be freed from noise by using a video bandwidth that is small com-
pared with the resolution bandwidth, and thus be measured more accurately.
RMS/Average detector and VBW
If an RMS or average detector is used, the video bandwidth in the hardware is
bypassed. Thus, duplicate trace averaging with small VBWs and RMS or average
detector no longer occurs. However, the VBW is still considered when calculating the
"Sweep Time" . This leads to a longer "Sweep Time" for small VBW values. Thus, you
can reduce the VBW value to achieve more stable trace curves even when using an
RMS or average detector. Normally, if the RMS or average detector is used the "Sweep
Time" should be increased to get more stable traces.
8.5.1.3
Coupling VBW and RBW
The video bandwidth can be coupled to the resolution bandwidth automatically. In this
case, if the resolution bandwidth is changed, the video bandwidth is automatically
adjusted.
Coupling is recommended if a minimum "Sweep Time" is required for a selected reso-
lution bandwidth. Narrow video bandwidths require longer "Sweep Time" s due to the
longer settling time. Wide bandwidths reduce the signal/noise ratio.
Table 8-1: Overview of RBW/VBW ratios and recommendations for use
Ratio RBW/VBW
Recommendation for use
1/1
Recommended for sinusoidal signals
This is the default setting for automatic coupling.
0.1
Recommended when the amplitudes of pulsed signals are to be measured
correctly. The IF filter is exclusively responsible for the pulse shape. No
additional evaluation is performed by the video filter.
10
Recommended to suppress noise and pulsed signals in the video domain.
Manually set (0.001 to 1000) Recommended for other measurement requirements
8.5.1.4
Coupling Span and RBW
The resolution bandwidth can be coupled to the span setting, either by a manually
defined factor or automatically. If the span is changed, the resolution bandwidth is
automatically adjusted. The automatic coupling adapts the resolution bandwidth to the
currently set frequency span/100.
The 6 dB bandwidths 200 Hz, 9 kHz and 120 kHz and the available channel filters are
not changed by the coupling.
With a span/RBW ratio of 100 and a screen resolution of 1000 pixels, each frequency
in the spectrum is displayed by 10 pixels. A span/RBW ratio of 1000 provides the high-
est resolution.
Bandwidth, Filter and Sweep Configuration
