R&S FSH3 Setting and Using the Measurement Functions
• The RMS detector is recommended. This ensures that the true power is always obtained
irrespective of the shape of the signal 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 so 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 still 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, it is not possible for the trace to
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.
¾ Press the LEVEL ADJUST softkey.
The R&S FSH3 starts the measurement of the optimal
reference level using a resolution bandwidth of 1 MHz,
a video bandwidth of 1 MHz and the peak detector.
During the measurement, the message "Adjusting level
for channel power measurement, please wait... " is
output.
The optimal reference level is then set.
Setting the channel bandwidth:
The channel bandwidth specifies the frequency range about the center frequency, over which the
R&S FSH3 performs the power measurement.
¾ Press the CHAN BW softkey.
The value entry box showing the current channel
bandwidth setting opens.
¾ Using the number keys enter a new channel
bandwidth and terminate the entry with the
appropriate unit, or
¾ Using the rotary knob or the cursor keys, change
the measurement time and confirm with the
ENTER key or the CHANNEL BW softkey.
The R&S FSH3 automatically sets the appropriate
span for the channel bandwidth that has been entered
(span = 1.2 x channel bandwidth) to ensure that no
incorrect channel power measurements are made.
The minimum channel bandwidth that can be set is
8.33 kHz. If you attempt to enter a smaller channel
bandwidth, the R&S FSH3 will automatically set
8.33 kHz and output the message “Out of range”.
1145.5973.12 4.35 E-6
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