Itu-R Multiplex Power Controller - Orban OPTIMOD-FM 8500S Operating Manual

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OPERATION

ITU-R Multiplex Power Controller

control will usually need to be set substantially below 0 dB unless
L D
IMITER R
the preset is quiet (like one of the
• When setting up an HD Radio facility, set the
adjust the
HD L
IMITER
channel to the loudness of the FM channel at the receiver.
In an HD Radio receiver, the HD channel has 5 dB higher gain than the ana-
log FM channel. Because the digital channel's loudness must match the FM
channel during receiver crossfades, there is no need to over-process the HD
channel; you can take advantage of the 5 dB of "bonus loudness" in this
channel to do 5 dB less peak limiting compared to the FM channel. Do not
match the loudness by turning down the Out Level control of the 8500S out-
put driving the HD exciter. This will force you to use unnecessarily large
amounts of limiter gain reduction, which will waste the "bonus loudness."
HD "loudness wars" will not only reduce quality but will also cause unbal-
anced, obtrusive crossfades between the analog and digital channels in the
radio. To brand your station's sound, you can choose the precise coloration
you want on the digital channel. You can still take advantage of all of the ar-
tistic choices implicit in stereo enhancer, equalization, and multiband com-
pression / limiting settings. Yet you do not need to use excessive peak limiting,
which can only reduce quality.
HD De-Ess allows you to mix an adjustable amount of the high frequency limiter
gain control signal into Band 5 of the HD processing only. This control allows you to
reduce the high frequency response of the HD processing channel in a program-
adaptive manner and is intended to reduce strong sibilance ("ess" sounds) that
might otherwise sound obtrusive. Higher (less negative) numbers give more de-
essing action but will also be more likely to reduce "sparkle" with music. If you no-
tice excessive sibilance, we recommend that you start by setting the control at –18.0
and fine-tune it to taste from there. Once you have set the HD D
your liking, save the resulting preset as a User Preset.
The default setting is –18, which provides a good compromise between
brightest sound (which would be accomplished by setting the control to
OFF) and control of high frequency artifacts that low bitrate codecs in-
troduce.
Starting with V2.0 software, Band 5 in the HD processing chain has its
own gain control sidechain that is independent of the FM processing
chain. Therefore, you can activate the HD Band 5 compressor to either
complement or replace the control that the HD DE-ESS control provides.
The ITU-R recommends that the power in the composite baseband signal (including
the pilot tone), integrated over any 60-second interval, not exceed the power in a
C
LASSICAL
in the on-air preset to match the loudness of the HD
D
RIVE
ORBAN MODEL 8500S
presets).
control to 0 dBFS. Then
O L
UT EVEL
-E
E SS
control to