R&S FSH
Measuring the Carrier-to-Noise Ratio
1145.5973.12 4.55
E-11
Operating sequence:
If the reference measurement is active, press the
CHANNEL BW softkey.
An entry box showing the current channel bandwidth
setting opens.
Enter the reference channel bandwidth using the
numeric keys and terminate your entry with the
appropriate unit key, or
Set the channel bandwidth with the rotary knob or
the cursor keys.
The R&S FHS automatically adapts the span to the set
channel bandwidth.
The minimum settable channel bandwidth is 8.33 kHz with the R&S FSH3 models 1145.5850.03 and
1145.5850.13.
If you attempt to enter a smaller channel bandwidth, the R&S FSH will automatically set 8.33 kHz and
output the message "Limit exceeded".
With the R&S FSH3 model 1145.5850.23 and the R&S FSH6, the minimum channel bandwidth is
833 Hz.
Setting the analyzer reference level for the reference channel measurement
When selecting the reference level, make sure that the R&S FSH is not overdriven. Since the power is
measured with a resolution bandwidth that is small in comparison with the signal bandwidth, the
R&S FSH may be overdriven although the trace is within the measurement diagram. To prevent the
R&S FSH from being overdriven, the signal can be measured at the largest possible resolution
bandwidth using the peak detector. If this setting is selected, the trace must not exceed the reference
level.
To simplify operation and to prevent incorrect measurements, the R&S FSH offers an automatic routine
for setting the analyzer reference level.
If the reference channel measurement is active (the
REF MEASURE softkey is highlighted in green),
press the LEVEL softkey.
Confirm the LEVEL ADJUST selection with the
ENTER key.
The R&S FSH starts the routine for determining the
optimum reference level using a resolution bandwidth
of 1 MHz, a video bandwidth of 1 MHz and the peak
detector. During the measurement routine, a
corresponding message is displayed.
The optimum reference level is then set.
Inserting the C/N reference
If the reference measurement has been activated, the R&S FSH inserts the reference power or the
reference level at the bottom of the measurement diagram. Usually this does not obscure the trace.
However, if the trace is in this area of the screen, the reference display can be blanked out.
