Level Control Before The Stl; Using The Orban 8100Ast (Or 8100A/St) Studio Chassis With The 8200; Stl And Exciter Overshoot - Orban OPTIMOD-FM 8200 Operating Manual

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OPTIMOD-FM 8200
INTRODUCTION

Level Control Before the STL

If the audio link between the studio and the transmitter is noisy, you can minimize the
audibility of this noise by performing the gain-riding function at the studio site. Gain-riding
applied before the link to the transmitter improves the signal-to-noise ratio because average
level on the link will be greater, so its noise will have less effect on the overall noise level
of the broadcast.
You can use the Orban Co-Operator 464A to perform OPTIMOD-FM's AGC function
before the STL. The 464A also contains high-frequency and peak control circuitry to protect
the STL transmitters or digital encoders from over-modulation.
When you use any studio level controller, defeat the gain-riding function in the main 8200
processing. This is covered in the setup information in Section 2 (page 2-46 or 2-56).
If you are using an Orban 4000 Transmission Limiter to protect your STL, do not defeat the
gain-riding function in the main 8200 processing. The Orban 4000 is a transmission system
overload protection device; it is normally operated below threshold. It is not designed to
perform an AGC or gain-riding function, and cannot substitute for the AGC function in the
8200.

Using the Orban 8100AST (or 8100A/ST) Studio Chassis with the 8200

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 8200 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 8200 and the 8100A1 (or 8100A/1)
transmitter chassis in parallel. This is usually practical, although complications will occur if
you are not using an Orban 8100AXT2 (or 8100A/XT2) Six-Band Limiter Accessory with
your 8100A1 (or 8100A/1), because, to correctly drive an 8200, 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
overshooting. There are similar requirements for FM exciters. Nevertheless, in some
installations some overshoot is inevitable. If this is a problem in your installation, the 8200's
remote control feature offers the means to reduce the peak level of the 8200's audio output
as necessary.
This way, you can still use the 8200's line-up tone to adjust the steady-state deviation to
± 75kHz. Yet the reduced peak level of the audio emitted from the 8200 ensures that the
carrier deviates no further than ± 75kHz after overshoot.
This overshoot reduction can be selected on the SYSTEM SETUP I/O CALIB screen.