Orban OPTIMOD 6200, Operating Manual

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OPTIMOD OPERATION
3-13
controlled to accommodate the very limited dynamic range of the medium, and that little
gain riding is therefore required from the 6200.
The Protection Limiter Structure
The Protection Limiter structure is designed for stations wanting the highest possible
fidelity to the source, such as a station broadcasting concert music at night when its au-
dience is likely to listen in a concentrated and critical way. Unlike the other structures,
the Protection Limiter structure is not designed to reduce the dynamic range, to increase
program density, to increase loudness, or to increase the consistency of sound from dif-
ferent sources. Its only function is to protect the transmitter from over-deviation while
preserving the spectral and dynamic quality of the source material.
The Protection Limiter structure is designed for operation below the threshold of limit-
ing most of the time. There are virtually no user controls — the parameters of the struc-
ture have been chosen to make it audibly undetectable.
There are two Factory Presets for the Protection Limiter structure.
PROTECTION 0dB
sets the limiting threshold so that limiting almost never occurs, while
PROTECTION 5dB
sets the limiting threshold so that program material at the maximum normal input level
(as determined by a PPM or VU meter monitoring the input program line) produces an
average limiting of 5dB.
Setting Up the Protection Limiter
To set up the Protection Limiter, recall preset
PROTECTION 0dB
if you want limiting to
occur only when the program level exceeds the maximum normal input level as deter-
mined by a PPM or VU meter monitoring the input program line. Recall preset
PROTECTION 5dB
if you want about 5dB of limiting to occur at the maximum normal
input level.
The
LESS-MORE
control affects only the input drive, and you can use it to set a nominal
limiting level different than 0dB or 5dB.
There are only two
FULL CONTROL
parameters for the Protection Limiter:
PROT
DRIVE (Protection Limiter Drive) level duplicates the effect of the LESS-MORE control,
and
LO PASS
sets the bandwidth of the processor.
As with all of the other LO PASS parameters within presets, the lowest of the
settings of this parameter, the MAX LPF filter parameter (in the Setup page),
and the LPF parameter (as programmed into a remote interface input) pre-
vails. In all cases, setting a 32kHz output sample frequency will also limit
the filter cutoff frequency to 15kHz or lower, regardless of the setting of any
of the other parameters above.