junger d07 Operation Manual page 77

FM-TRANSMISSION – d07
There are two important parameters for FM-Transmission
The frequency deviation, determined by the peak level of the signal
The MPX-Power, determined by the energy of the signal
International standards regulate the maximum values that have to be kept tight so
that neighbouring transmitters will not be disturbed.
Frequency deviation
MPX-Power
The job of the d07 processor is standard compliance controlling of FM signal
energy within permissible peak deviation.
The compression of the program signal causes an increase of the signal energy
and, therefore, more loudness, but also more modulation power (MPX power). Too
much compression will cause the permissible value of the multiplex power to be
exceeded and the MPX limiter must reduce the total signal. As a consequence, the
peak levels as well as the average levels are reduced, leading to a reduced
loudness, as outlined below :
Input
Compressor
peak
level
compression
MPX
level
Input signal
It is necessary to break up this "vicious circle" by optimal setting of GAIN and
compression. The optimisation of parameters should be done in a way that neither
the peak limiter nor the MPX-limiter permanently show GAIN-REDUCTION. The
program signal limitation should only occur briefly in order not to deprive it of all
dynamic properties. The average modulation power can only be optimized by
tweaking linear GAIN and the COMPRESSOR as well.
+75kHz
0 dBr
Peak limiter
peak
reduction
compressor out peak limiter out
Oputput
MPX limiter
MPX power
reduction
MPX limiter out
B 7 FM-Transmission d07
7
B
7.1.
General
7.2.
MPX-
Limiter