Measuring the Carrier-to-Noise Ratio R&S FSH
1145.5973.12 4.58 E-11
Setting the noise channel bandwidth
Enter the noise channel bandwidth with the CHANNEL BW softkey. Make the entry after the noise
channel measurement has been activated. This is the case when the NOISE MEASURE softkey is
highlighted in green.
Note: During the reference channel measurement, the REF MEASURE softkey is highlighted in green.
The R&S FSH indicates the channel limits by means of two vertical display lines.
If the noise channel measurement is active, press
the CHANNEL BW softkey.
The R&S FSH opens the entry box for the channel
bandwidth (CHAN BW) with the noise channel
bandwidth just selected.
Using the numeric keys, enter the noise channel
bandwidth and terminate your entry with the
appropriate unit key, or
Set the noise 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, the R&S FSH6 and the R&S FSH3-TV, the minimum channel
bandwidth is 833 Hz.
Setting the R&S FSH reference level during noise channel measurement
When selecting the reference level, make sure that the R&S FSH is optimally set with regard to the
input signal. It must be set to be as sensitive as possible (corresponds to a low reference level) without
being overdriven to ensure optimum C/N measurement results. This is the case when the measured
noise power is at its lowest or the C/N ratio at its highest.
To simplify operation and to prevent incorrect measurements, the R&S FSH has an automatic routine
for setting the reference level.
If the noise channel measurement is active (the
NOISE 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. During the measurement
routine, a corresponding message is displayed.
The optimum reference level is then set.
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