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INTRODUCTION ORBAN Model 8400
Stereo Analog Baseband Composite Output
The stereo encoder has two unbalanced analog baseband outputs on two BNC connectors
on the rear panel. Each output can be strapped for 0 or 75Ω source impedance, and can
drive up to 8V peak-to-peak into 75Ω in parallel with up to 0.047μF (100ft/30m of RG-
59/U cable) before any significant audible performance degradation occurs (see footnote
on page 1-12 and refer to Fig. 2-3 on page 2-10). Independent level control of each out-
put is via software in the
Input/Output: Composite screen. A ground lift switch is avail-
able on the rear panel. This is useful to prevent ground loops between the 8400 and the
transmitter.
The second composite output can be reconfigured in software to provide the stereo pilot
tone only, which can provide a pilot reference for an RDS subcarrier generator.
Subcarriers
The stereo encoder has two unbalanced 600Ω subcarrier (SCA) inputs with rear-panel
BNC connectors to accept any subcarrier at or above 23 kHz. The subcarriers are mixed
into each composite output. Their level will not be affected by the composite level con-
trol for that output.
The mixing occurs after D/A conversion and is analog. Subcarriers are not
digitized by the 8400.
The gain from the subcarrier input to the composite output is fixed at –20 dB. Therefore,
the gain is scaled so that 1.5V peak at the subcarrier input produces 10% subcarrier injec-
tion with reference to 3.0Vp-p=100% modulation of the FM carrier. This –20 dB gain
minimizes the effect of any noise picked up on the subcarrier input cable while still ac-
commodating most subcarrier generators.
The correct peak level of the stereo program applied to the stereo encoder sometimes de-
pends on the number of subcarriers in use. Some regulatory authorities require that total
baseband peak modulation be maintained within specified limits. Thus, the level of the
stereo main and subchannel must be reduced when a subcarrier is turned on. The 8400’s
remote control feature allows you to reduce the stereo main and sub-channel level by
connecting an on/off signal from your subcarrier generator (See page 2-9). You define
the
amount of reduction in % on the Input/Output screen (See page 2-32). See page 2-51
for information on programming the remote control.
Remote Control Interface
The Remote Control Interface is a set of eight optically isolated inputs on a dB-25 con-
nector that can be activated by 5-12V DC. They can control various functions of the
8400:
• Recall any Factory Preset, User Preset, Test Mode state (Bypass or Tone), or exit
from a Test Mode to the previous processing preset.
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