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4.2 Operation and features SPM-32A ... SPM-36A
5 Hz bandwidth
The analog radio signals used to indicate the zone and to signal
broadcast announcements in the ARI system (used on highways
in Germany and other countries) lie very close to the 57 kHz
auxiliary carrier.
These signals can be measured precisely with the 5 Hz
bandwidth. This is also useful for measurement of spectral lines
in the new digital radio data system (RDS).
Fig. 4-13 Typical receiver selectivity at a bandwidth of 5 Hz
25 Hz bandwidth
This narrow bandwidth filter is suitable for measuring
–
pilot levels or carrier leaks
,
– unkeyed signals in VFT channels,
– the modulation frequency (= half transmission frequency)
as a spectral line,
– interference signals inside and outside the VFT channel.
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