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INTRODUCTION ORBAN Model 8400
Some consultants presently offer modifications to minimize or eliminate this problem. If
your exciter or STL has this problem, you may contact Orban Customer Service for the
latest information on such services.
Analog Landline (PTT/post office line)
Analog landline quality is extremely variable, ranging from excellent to poor. Whether
landlines should be used or not depends upon the quality of the lines locally available,
and upon the availability of other alternatives. Even the best landlines tend to slightly veil
audio quality, due to line equalizer characteristics and phase shifts. They will certainly be
the weakest link in a FM broadcast chain.
Slight frequency response irregularities and non-constant group delay characteristics will
alter the peak-to-average ratio, and will thus reduce the effectiveness of any peak limiting
performed prior to their inputs.
Using the Orban 8100AST (or 8100A/ST) Studio Chassis with
the 8400
If you have an OPTIMOD-FM 8100A1 (or 8100A or 8100A/1) installation that uses an
Orban 8100AST (or 8100A/ST) Studio Chassis at the studio to protect an STL (with the
main 8100A, 8100A1 or 8100A/1 chassis at the transmitter), you may wish to continue to
use the Studio Chassis to protect the STL when you install the 8400 at the transmitter.
If you are keeping your analog OPTIMOD-FM as a standby processor, you will probably
want to use the Studio Chassis to drive both the 8400 and the 8100A1 (also called
8100A/1) transmitter chassis in parallel. This is usually practical, although complications
will occur if you are not using an Orban 8100AXT2 (also called 8100A/XT2) Six-Band
Limiter Accessory with your 8100A1, because, to correctly drive an 8400, the Studio
Chassis must be strapped as if it were driving an 8100A1 (or 8100A/1) + 8100AXT2 (or
8100A/XT2) system. Therefore, if you have only an 8100A1 (or 8100A/1), you will have
to re-strap the Studio Chassis for operation without the XT2 before you can put the
standby 8100A1 (or 8100A/1) on the air.
STL and Exciter Overshoot
Earlier in this section, we discussed at length what is required to prevent STLs from over-
shooting. There are similar requirements for FM exciters. Nevertheless, in some installa-
tions some overshoot is inevitable. If this is a problem in your installation, the 8400’s
remote control feature offers the means to reduce the peak level of the 8400’s audio out-
put as necessary. This way, you can still use the 8400’s line-up tone to adjust the steady-
state deviation to ±75 kHz. Yet, the reduced peak level of the audio emitted from the
8400 ensures that the carrier deviates no further than ±75 kHz after overshoot. This over-
shoot reduction can be selected on the Input/Output screen, and the remote operation can
be selected in System Setup: Network/Remote.
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