Orban OPTIMOD-AM 9300, Руководство по эксплуатации

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OPERATION ORBAN MODEL 9300
OPTIMOD-AM Processing
OPTIMOD-AM processing occurs in the following main stages.

A gentle AGC that is ordinarily used to slowly ride gain, keeping long-term aver-
age drive levels into the following multiband compressor stage constant.

A program equalizer. This starts with a three stage parametric equalizer that al-
lows you to adjust bass, midrange, and high-frequency equalization. There are
three fully parametric sections, each with non-interacting control over the
amount of EQ (in dB), the bandwidth, and the center frequency. They are used
to color the audio to achieve a “signature sound” for the station.
The program equalizer also contains a high frequency shelving section we call
the “receiver equalizer.” While the parametric equalizers are designed to pro-
duce program coloration as desired, the HF shelving section of the program
equalizer is ordinarily used to pre-emphasize the signal to help overcome the
high-frequency rolloff of typical AM radios. The shelving section can be oper-
ated as a fixed, first-order shelf to provide NRSC standard preemphasis or as a
third-order semi-parametric shelf with adjustable gain and curve shape. In gen-
eral, if you use a great deal of HF boost, you will have to turn down the
L
ESS
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M
ORE control to avoid audible distortion.

A five-band compressor with Orban's exclusive multiband distortion-cancelling
clipper. This system embeds the clipper within the multiband crossover to permit
the crossover to filter out clipping distortion products that would otherwise be
audible. A feedforward sidechain provides further, highly selective cancellation
of difference-frequency intermodulation distortion. The five-band compressor
also incorporates a single-ended dynamic noise reduction system, which can be
activated or defeated as desired.

A safety clipper and overshoot compensator. These elements precisely control
peak modulation without adding out-of-band frequencies, as a simple clipper
would.

A transmitter equalizer with four presets. The TX EQ allows you to pre-distort
OPTIMOD-AM's output waveform to compensate for low-frequency tilt,
high-frequency ringing, and high-frequency group delay distortion in the trans-
mitter and antenna system. The active transmission preset also determines the
positive peak threshold and the highpass filter and lowpass filter cutoff fre-
quencies,
AM Processing: The Art of Compromise
Noise, interference, and narrow bandwidth inherently restrict AM audio quality. Be-
cause of this, purist goals (“the output should sound just like the input”) are irrele-
vant because receiver design makes them impossible to achieve. Instead, the goal of
processing should be to deliver the highest subjective quality through this limited
transmission channel to the listener's ear. This always requires substantial compres-