R&S FSH
Spectrum Analyzer Mode
Configuring Spectrum Measurements
Operating Manual 1173.6275.12 - 30
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3.2.2.5 Setting the RF Attenuation
RF attenuation adjusts the input range inside the analyzer. It is coupled directly to the
reference level. If you have set a high reference level, RF attenuation is turned on in
10 dB steps according to the table below so that the input mixer always remains in the
linear range.
The R&S FSH provides three attenuation modes.
● Auto Low Distortion
If this mode is active, the R&S FSH sets the RF attenuation 10 dB higher
according to the table below, making the stress of the input mixer 10 dB less at the
specified reference level. If the spectrum is densely occupied with signals, e.g. in a
television cable network, the input mixer reduces the R&S FSH inherent spurious
products. However, the inherent noise display of the R&S FSH increases due to
the increased attenuation in front of the input mixer.
● Auto Low Noise
If this mode is active, the R&S FSH sets the RF attenuation 10 dB lower. This
increases the sensitivity of the R&S FSH, which means that the inherent noise
display decreases due to the lower attenuation in front of the input mixer.
● Manual
Manual selection of the attenuation.
You can check the status of the RF attenuation and the preamplifier in the
measurement setup dialog and the hardware settings area of the display.
Reference Level
Preamplifier OFF
Preamplifier ON
RF Attenuation
RF Attenuation
Low Noise
Low Distortion
Low Noise
Low Distortion
≤-30 dBm
0 dB
0 dB
0 dB
0 dB
-29 to -25 dBm
0 dB
0 dB
0 dB
5 dB
-24 to -20 dBm
0 dB
0 dB
0 dB
10 dB
-19 to -15 dBm
0 dB
5 dB
5 dB
15 dB
-14 to -10 dBm
0 dB
10 dB
10 dB
20 dB
-9 to -5 dBm
5 dB
15 dB
15 dB
25 dB
-4 to 0 dBm
10 dB
20 dB
20 dB
30 dB
1 to 5 dBm
15 dB
25 dB
25 dB
35 dB
6 to 10 dBm
20 dB
30 dB
30 dB
40 dB
11 to 15 dBm
25 dB
35 dB
35 dB
40 dB
16 to 20 dBm
30 dB
40 dB
40 dB
40 dB
21 to 25 dBm
35 dB
40 dB
40 dB
40 dB
26 to 30 dBm
40 dB
40 dB
40 dB
40 dB
