junger d07 Operation Manual page 78

Level
diagramm
Peak Level
Operation
Level
MPX-Limiter
Setup hint
For alignment of the d07 it is important to consider the level diagram of the overall
transmission chain (see below):
Frequency deviation - FM transmitter
kHz
FM - peak deviation
75,0
Peak deviation without pilot tone
68,3
Reference deviation
40,0
30,0
19,0
12,0
Pilot tone level
6,7
ITU BS 416-6 / CCIR 412-5 defines MPX power as relative average of modulation power
mesured over a period of 60 sec. It shall be equivalent to the power of a stationary signal
that causes a frequency deviation of 19kHz
The threshold of the peak limiter (limiter threshold) determines the maximum output
level of the d07. This value is the most important setting parameter. It serves at the
same time as the reference point for the MPX limiter, the adaptive pre-emphasis and
the compressor.
An MPX level of 0dBr lies 11.1 dB below the limitation point of the limiter of the d07
and is fixed to it. This value is given by the relation of multiplex power level of 0dBr
(19kHz frequency deviation) to peak level (75kHz frequency deviation). For special
applications the MPX level can be changed by + 4dB respectively.
The operating level in standard studio environment is not the peak level but the
nominal level of +6dBu e.g. (analog) or –9dBFS (digital). This level will also be used to
line up the FM transmitter and shall cause a nominal modulation deviation of +40kHz.
The headroom of 4.6dB left to the peak level (peak deviation respectively) can be
exploited for temporary signal peaks or for the pre-emphasis of higher signal
frequencies.
With a given nominal level the threshold of the peak limiter may not exceed this
nominal level by more than +4.6dB because otherwise the peak frequency deviation
level will be exceeded. Therefore the transmission path must be aligned in a way that
the nominal output level of the d07 will generate a signal at the output of a MPX-
encoder that causes a deviation of +40kHz. Afterwards the peak limiter of the d07
must be set so that the peak deviation is limited to +75kHz.
alignment
reference level
+4dB
r
0dB
r
-4dB
r
Audio level - output of d0 7
Peak limiter reference point
+4,6 dB
-6,5dB
dBFS
-4,4dBFS
Peak level
+6dBu / -9dBFS
Operating level
-11,1dBFS
MPX level
below peak
level