Setting The Reference Level; Setting The Channel Bandwidth; Changing The Span - Rohde & Schwarz FSH4 Operating Manual

R&S FSH
2.1.1.2

Setting the Reference Level

The reference level is the power level that the R&S FSH expects at the RF input. When
selecting the reference level, make sure that you do not overload the R&S FSH by
applying a signal whose power exeeds the maximum reference level.
As the power is measured with a small resolution bandwidth compared to the signal
bandwidth, it is still possible to overload the R&S FSH, even if the trace is within the
measurement diagram. To prevent an overload, perform the measurement with the
largest resolution bandwidth possible using the peak detector. If you set these
parameters, it is not possible for the trace to exceed the reference level.
To simplify operation and to prevent incorrect measurements, the R&S FSH has an
automatic routine for setting the reference level.
M Press the SCALE/AMPT key.
M Press the "Level Adjust" softkey.
The R&S FSH performs a
measurement to determine the
optimal reference level.
It uses a resolution bandwidth of 1 MHz, a video bandwidth of 1 MHz and the peak
detector. After finishing the automatic measurement, the R&S FSH sets the optimal
reference level.
2.1.1.3

Setting the Channel Bandwidth

The channel bandwidth specifies the frequency range around the center frequency,
over which the R&S FSH performs the power measurement.
M Press the MEAS key.
M Press the "Chan BW" softkey.
The R&S FSH opens an input field to specify the channel bandwidth.
M Enter the channel bandwidth you need.
The R&S FSH sets the appropriate span for the channel bandwidth that you have
entered (span = 1.2 x channel bandwidth). This ensures that no incorrect channel
power measurements are made.
The minimum channel bandwidth that you can set is 833 Hz at a span of 1 kHz.
2.1.1.4

Changing the Span

Usually, the span the R&S FSH sets yields optimal results. But sometimes you also
need to see the spectrum outside the current span to detect other signal components
that you need to include in the measurement. Therefore, you can adjust the span to up
to ten times the channel bandwidth and hence still be able to see the spectrum outside
the measurement channel.
Operating Manual 1309.6275.12 - 14
Spectrum Analyzer Mode
Performing Spectrum Measurements
44