Orban OPTIMOD-FM 8500S, Руководство по эксплуатации

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OPERATION ORBAN MODEL 8500S
erage power of the sinewave that produced
±
19 kHz carrier deviation. In other
words, whenever you start measuring , you must not exceed the total integrated
power limit over the following 60 seconds.
This makes it impractical to "bank" power over the full 60-second window. For ex-
ample, at first glance one might think that a classical music station could exploit a
period of quiet music to allow a crescendo to get louder than it would using the
8500S's relatively fast integration time. However, what happens if someone starts an
arbitrary 60-second measurement period not at the beginning of the quiet passage
but at the beginning of the crescendo?
Because an automatic MPX power controller does not know what is coming after
the crescendo, it must reduce the level of the crescendo so that it complies with the
MPX requirement over with an integration time that is shorter than 60 seconds.
Otherwise, it might have to dramatically reduce the level of following (as yet un-
known) program material in order to ensure that the MPX power limit is not ex-
ceeded over the 60-second measurement period in question. This kind of gain
pumping would be far worse than the pumping produced by using a relatively short
integration time.
Multiplex Power Control in Stand-Alone Stereo Encoder Mode
When you use the 8500S in stand-alone stereo encoder mode, we recommend set-
ting up your transmission system to produce approximately 3 dB of average MPX
power control. This avoids unnatural loudness variations.
To achieve this goal when an Optimod-FM drives the 8500S stereo encoder, reduce
the drive into the Optimod’s peak limiters by turning down the
M
ULTIBAND
C
LIPPING
control in the on-air preset until the MPX Power gain reduction meter on the 8500S
indicates an average of 3 dB of gain reduction. Save the result as a User Preset.
Do not reduce the drive level to the 8500S by turning down the driving Optimod’s
output level control because this does not decrease distortion in the Optimod’s peak
limiter, unlike turning down the
M
ULTIBAND
C
LIPPING
control .