Itu-R Multiplex Power Controller; Multiplex Power Threshold - Orban Optimod-FM 8300 Operating Manual

OPTIMOD-FM DIGITAL
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HD Eq Gain determines the depth of high frequency shelving equalization pro-
duced by the parametric HF shelving equalizer, which is located before the look-
ahead limiter.
This equalizer is sometimes useful for reducing the audible disparity be-
tween the FM and digital-channel outputs. The digital-channel output
receives no high frequency limiting or clipping and may therefore be as
much as 6 dB brighter than the FM output. If you wish to reduce this dif-
ference to smooth out the audible difference between the two channels
during a receiver crossfade, you can apply HF rolloff to the digital-
channel channel by ear. Another reason you might want to do this is if
the digital-channel channel sounds excessively bright after you have op-
timized the 8300's tuning for FM..
Yet another reason to use HF rolloff in the digital-channel channel is to
reduce codec artifacts at the high frequencies—the familiar "watery"
sound.
The parametric HF shelving equalizer can only produce HF rolloff. It can-
not boost.
HD Eq Freq sets the corner frequency of the parametric HF shelving equalizer.
HD Limiter Dr sets the drive level to the digital-channel look-ahead limiter.
The factory default is
Because its loudness must match the FM channel, there is no need to
over-process the digital channel. HD "loudness wars" will not only reduce
quality but will also cause unbalanced, 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 artistic choices implicit in stereo
enhancer, equalization, and multiband compression / limiting settings.
Yet you do not need to use excessive peak limiting, which can only re-
duce quality.

ITU-R Multiplex Power Controller

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
sinewave that modulates the FM carrier to 19 kHz (25.3% modulation re ±75 kHz
deviation). Many European countries are now enforcing this recommendation. (See
ITU-R 412 Compliance on page 3-9 for more information.)

Multiplex Power Threshold

Your Optimod provides a means to limit the integrated multiplex power to the ITU
standard by a closed-loop technique that allows you to use any preset and to create
customized presets freely. The multiplex power controller is adjusted via the ITU412-
9 control (see step 20 on page 2-22). Set it OFF if your country does not enforce the
standard.
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