Junger Audio d07 - Digital Transmission Processor - Manual (Page 62)

For alignment of the d07 it is important to consider the level diagram of the overall
transmission chain (see below):
The ceiling level 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 and the adaptive pre-emphasis.
An MPX level of 0dBr lies 10.9 dB below the ceiling level 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 40 kHz.
The headroom of 4.4 dB 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 +4.4dB because otherwise the peak frequency deviation
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 and ceiling of the d07
must be set so that the peak deviation is limited to 75kHz.
The dynamically performance of the MPX limiter can be changed with the parameter
PROCESSING (soft, mid, hard). The best MPX limiting can be achieved by varying
this parameter, depending on the programme characteristic,
Level
diagramm
Operation
Level
Peak Level
MPX-Limiter
Setup hint
0dB
r 19,0
40,0
Reference deviation
6,7
Pilot tone level
75,0
FM - max. peak deviation
Peak limiter reference
-4,6dBFS 66,3
max. deviation without pilot / RDS
kHz
Operating level
+4,4 dB
ITU BS 416-6 / CCIR 412-5 defines MPX power as rrelative 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
-6,5dB
alignment
reference level
+6dBu / -9dBFS
Ceiling level
-15,5dBFS
MPX level
10.9dB below
Ceiling level
Frequency deviation - FM transmitter Audio level - output of D07
dBFS
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Ceiling reference
>= 0dB