Orban Optimod-FM 8300 Operating Manual page 153

OPTIMOD-FM DIGITAL
The receiver will "see" this as stereo material, and will demodulate it as if
it were part of the stereo subchannel. Accordingly, harmonics of L+R ma-
terial will be frequency-shifted upon demodulation, and will no longer
bear a harmonic relationship to the material that produced them.
Mathematically, these harmonics will be located at the same frequencies
as harmonics caused by clipping in a simple digital-domain clipper (with
no anti-aliasing) operating at 38 kHz sample rate.
If you want to use the composite limiter more heavily, one option is to
trade off composite limiting against left/right domain overshoot com-
pensation. To do this, reduce the O
and increase the COMP DRV control setting proportionately. (The
O
VERSHOOT
Remote software.)
MPX POWER OFFSET operates only when the ITU-412 multiplex power controller is
active (and is thus irrelevant to users in countries that do not enforce this standard).
The control introduces a fixed loss before the FM analog peak limiting chain. If the
M P
ULTIPLEX OWER
0, the MPX P
OWER
control's setting. Resetting the M
change the loss. (For example, setting the M
will cause the loss to decrease by 3 dB.)
The M
P
ULTIPLEX OWER
Regardless of the setting of the
MPX P
ger than 0 dB.
The MPX P O
OWER
that the multiplex power controller might produce. These can occur because the ITU
specification does not call for psychoacoustic weighting. The Optimod does not
force the multiplex power controller to dynamically produce all of the required gain
reduction (which could vary widely, depending on the program material). Instead,
the MPX P
O
OWER
duction produced by the control is, of course, unchanging and cannot introduce au-
dible artifacts.
The ideal dynamic gain reduction for the multiplex power controller is 2 to 3 dB
with typical program material. However, the actual gain reduction will vary widely
depending on whether the underlying processing preset is "loud" or "quiet." There-
fore, the appropriate setting of the MPX P
what preset is in use. Accordingly, each preset has its own setting of the MPX P
, which is a processing parameter like any other in a given preset. Hence, ad-
O
FFSET
justments that affect the multiplex power controller appear in two independent
places in the Optimod: The M
control, while the MPX P
Depending on the preset, the MPX P
dB (no effect) to as much as –9 dB. If you customize a preset in any way (including
using L ), you may wish to trim the MPX P
-M
ESS ORE
that the multiplex power controller produces 2-3 dB of indicated gain reduction
with typical program material. This will achieve the maximum on-air loudness that
C D
OMPENSATOR RIVE
control (in the I
T
HRESHOLD
control produces the same amount of loss (in dB) as this
O
FFSET
ULTIPLEX
control can only introduce loss, never gain.
T
HRESHOLD
O
controls, the resulting gain offset can never be lar-
OWER FFSET
control's purpose is to reduce unnatural loudness variations
FFSET
control produces most of the gain reduction. The gain re-
FFSET
ULTIPLEX
is part of the on-air preset.
O
OWER FFSET
OWER
C
VERSHOOT OMPENSATOR
control is accessible only from the 8300 PC
/ U
/O
NPUT UTPUT
control away from 0 will
P T
OWER HRESHOLD
P T
ULTIPLEX OWER
M P
ULTIPLEX OWER
control depends strongly on
O
OWER FFSET
control is a system setup
P T
OWER HRESHOLD
control's setting can vary from 0
O
FFSET
O
OWER FFSET
OPERATION
D control
RIVE
screen) is set to
TILITIES
control to +3
HRESHOLD
T
and
HRESHOLD
OWER
for that preset so
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