Orban OPTIMOD-FM 5518, Operating Manual

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5518-FM DIGITAL INSTALLATION
2-19
you are driving the 5518 with a digital OPTIMOD-FM, use its lineup tone oscil-
lator.
C) Navigate to
Setup > I/O C
ALIB
> D
IG
I
N
C
ALIB
> DI R
EF
.
Adjust the
DI R
EF
control
to produce 100% composite modulation (usually
±
75 kHz carrier deviation) as
indicated on a modulation monitor or analyzer connected to your FM trans-
mitter’s output.
24. Activate the L/R Peak Limiter (optional)
A) Press the
Modify
button
.
B) If you do not see the
L/R L
IM soft button, press the
Next
button until it ap-
pears.
C) Set the control to
I
N .
This activates a peak limiter that controls peaks with a combination of
look-ahead limiting and band-limited clipping. There are two limiters,
operating independently on the left and right channels. They are in-
tended only to remove overshoots caused by the STL. If used for more
than 3 dB of peak reduction, they can cause audible side effects. To
minimize audible distortion, it always better to minimize overshoots in
the STL itself instead of relying on the L/R peak limiter to remove them.
25. Activate the Composite Limiter (optional)
To operate successfully in SSB/VSB mode, you must activate the composite lim-
iter.
A) Press the
Modify
button
.
B) If you do not see the
MPX L
IMIT
M
ODE soft button, press the
Next
button until
it appears. Then select either
H
ARD or
H
ALF
C
OS modes.
When operating as a hard clipper, the composite limiter will produce
maximum brightness in the frequency range from 5 to 15 kHz because,
unlike left/right audio-domain clippers, it can produce square waves in
this frequency range. The downside compared to Half-Cosine mode is
that it can noticeably compromise stereo imaging.
When operating in Half-Cosine mode, the composite limiter produces
somewhat less brightness but does not compromise stereo imaging. Be-
cause this mode produces lower subjective distortion, Orban’s factory
programmers prefer the sound of the Half-Cosine mode.
In either mode, the baseband output is overshoot compensated and
bandlimited to 53 kHz, unlike conventional composite clippers.
The
H
ARD mode is only available when the 5518 is operated as a stand-
alone stereo encoder. In the 5518’s audio processor mode, its composite
limiter always operates in Half-Cosine mode.
C) If you do not see the
MPX L
IM
D
R soft button, press the
Next
button until it
appears.
D) Adjust the control as desired.