Orban OPTIMOD-FM 8600Si, Operating Manual

Page: 248 / 356

3-82
OPERATION ORBAN MODEL 8600Si
The control is located in the Setup
> S
TEREO
E
NCODER screen because the regulation
applies to all operation of the processor in a given installation.
If your country enforces the standard, you should set the control to complement the
amount of peak overshoot in the transmission system following your Optimod. Set-
ting the control at “0” will correctly control the multiplex power when there is no
overshoot after the 8600Si. This will typically be true when you are using your Opti-
mod’s built-in stereo encoder to drive the transmitter directly.
Section 1 of this manual has an extensive discussion of overshoot in transmission
paths. See
Transmission from Studio to Transmitter on page 1-16 and following pag-
es.
Many paths have overshoot, and this forces you to reduce the average modulation
to avoid overmodulating the transmitter. This would reduce the multiplex power by
the same amount, forcing the multiplex power below the ITU requirement.
To compensate for this, match the
ITU412-9
control to the peak overshoot of the
transmission system following the 8600Si. For example, if RF peak deviation exceeds
the peak deviation produced by the 8600Si’s sinewave oscillator (set for 100%
Figure 3-4: Multiplex power over 15 minute observation interval
with Multiplex power controller active, measured at the Optimod’s composite output