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A07B500S manual
MODULATION MEASUREMENT
7.1
General information
The broadcast reception at frequency modulation is often made difficult because of the networks
exceeding crowding; the interferences due to the adjacent channels makes the listening unpleasant.
This inconvenient may be caused by an ignoring of the protection rules mentioned in the REC. ITU-
R BS.412-7 of which the remarkable graphs reported below:
300KHz far from the program we are listening, it must
The graph shows that if the interfering network is at
have a level higher than the maximum of 7dB, if it' s at 200KHz the field intensity level at the point
of listening, will be 6dB lower in monophonic or 7dB in stereophonic.
These values, expressed in dB as protection ratio, assume that the interfering network is
broadcasting with the maximum allowed spectrum width and this reaches the maximum at the
correspondence of peaks and the maximum modulation power. In a laboratory it' s possible to
simulate the worst example of modulation by modulating the transmitter, instead of dance-music,
Pag. 49
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