R&S FSH3 Setting and Using the Measurement Functions
Selecting a standard:
The R&S FSH3 offers a default for measuring the occupied bandwidth for different standards. It is also
possible to define and save user-specific configurations.
¾ Press the STANDARD softkey.
A table with the available standards opens.
¾ Using the rotary knob or the cursor keys, select the
appropriate standard.
¾ Confirm your selection with the ENTER key or the
STANDARD softkey.
The selected standard is set. The optimal span,
resolution bandwidth, video bandwidth, sweep time
and detector for the standard are selected
automatically.
If USER is selected, the R&S FSH3 restores the last setting used in the USER mode for measuring the
occupied bandwidth. The R&S FSH3 automatically makes changes to the setting so that it is again
available when USER is called again.
The following should be noted when changes to the settings are made:
• The span is always coupled to the channel bandwidth (CHANNEL BW). When changes are made,
the R&S FSH3 automatically sets the appropriate span (= 5 x channel bandwidth).
• The resolution bandwidth should be between 1 % and 4 % of the channel bandwidth. This ensures
that the occupied bandwidth is measured with high accuracy.
• The video bandwidth must be at least three times the resolution bandwidth. This prevents incorrect
results due to the compression of signal peaks by the video filter.
• The RMS detector is recommended. This ensures that the power measurement is always correct
irrespective of the waveform being investigated.
• The sweep time must be set so that the result is stable. If the sweep time is increased, the
R&S FSH3 also increases the integration time for the RMS detector and thus ensures more stable
measured values.
Setting the reference level:
When selecting the reference level, ensure that the R&S FSH3 is not overdriven. As the power is
measured with a resolution bandwidth that is small in comparison with the signal bandwidth, the
R&S FSH3 may still be overdriven even though the trace is within the measurement diagram. To
prevent the R&S FSH3 from being overdriven, the signal can be measured at the largest resolution
bandwidth possible using the peak detector. If this setting is selected, the trace may not exceed the
reference level.
To simplify operation and to prevent incorrect measurements, the R&S FSH3 has an automatic routine
for setting the reference level.
1145.5973.12 4.41 E-6
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