Orban OPTIMOD-FM 5518, Operating Manual

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2-22
INSTALLATION ORBAN MODEL 5518
29. Activate the 5518’s ITU-R BS412-9 multiplex power controller (optional).
[Skip this step if ITU-R BS412 is not enforced in your country. At the time of this
writing, it is only enforced in certain European countries.
If your country does
not enforce ITU-R BS412, set the ITU412-9 control to OFF.]
[Be sure that the multiplex power controller is turned off until you have finished
setting up the other stereo encoder parameters. Otherwise, it will interfere with
setting output levels.]
If you are driving the 5518 with an OPTIMOD-FM that includes a MPX power con-
troller and you need to obey BS412-9, turn on the MPX Power Controller in the
OPTIMOD-FM driving the 5518 and do not turn on the 5518’s MPX power con-
troller. This will minimize peak limiting artifacts in the OPTIMOD-FM. If your
BS412 modulation monitor indicates too much or too little MPX power, adjust
the
ITU412
control on the driving OPTIMOD-FM until the monitor indicates that
the power is being controlled correctly. Only if the MPX power changes as a
function of program material (which might occur if the path between the driving
OPTIMOD-FM and the 5518 introduces severe overshoots) should you activate
the 5518’s MPX power controller to correct this problem. In this case, adjust the
ITU412
control of the driving Optimod so that all program material produces at
least the maximum permitted MPX power. The MPX power controller in the 5518
will then only eliminate power overshoots caused by the STL instead of control-
ling all MPX power itself.
To activate the 5518 MPX power controller:
A) Navigate to
Setup > S
TEREO
E
NCODER
> Next > ITU412.
B) Set the multiplex power threshold by holding the
ITU412
button down and
turning the knob so that the display indicates 0.0 dB
.
If your transmission system introduces overshoot in the signal path after
the 5518 (including the transmitter), instead set the multiplex power
threshold so that it equals the amount of peak overshoot (in dB) in the
transmission system. If you do not do this, the 5518’s ITU-R BS412 control-
ler will set the average multiplex power too low.
The easiest way to measure system overshoot is to turn the multiplex
power controller off temporarily. Then set the 5518’s output level (using
its built-in 100Hz reference tone) so that the transmitter produces

75
kHz deviation. Finally, play program material with lots of high frequency
energy and bass transients (like bright rock music with heavy kick drum)
and observe the peak deviation produced by the program material. The
overshoot is the amount (in dB) by which the deviation with program
material exceeds

75 kHz deviation.
See ITU-R Multiplex Power Controller on page 3-4.
The following material provides detailed instructions on how to set up the 5518. If
QUICK SETUP does not fully address your setup needs or if you wish to customize
your system beyond those provided with QUICK SETUP, then you may need the addi-
tional information in the sections below. However, for most users, this material is