Subcarriers; Remote Control Interface - Orban Optimod-FM 8300 Operating Manual

1-8
INTRODUCTION

Subcarriers

Remote Control Interface

ance and can drive up to 8V peak-to-peak into 7in parallel with up to 0.047F
(100ft / 30m of RG-59 / U cable) before any significant audible performance degra-
dation occurs.
See the footnote on page 1-12 and refer to Figure 2-3 on page 2-9.
Independent level control of each output is via software (see step 6 on page 2-26). A
ground lift switch is available on the rear panel. This is useful to prevent ground
loops between the 8300 and the transmitter.
The stereo encoder has two unbalanced 60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 and their level is not affected by the compos-
ite level control for that output.
The 8300 does not digitize subcarriers; the mixing occurs after D/A conversion and is
analog.
Subcarrier inputs sum into composite baseband outputs before digitally controlled
composite attenuator. The sensitivity of the SCA 1 input is variable from 220 mV p-p
to >10 V p-p to produce 10% injection. Sensitivity is adjustable by an internal PC-
board-mounted trim pot. The sensitivity of the SCA 2 input is fixed at 772 mV p-p to
produce 10% injection.
The correct peak level of the stereo program applied to the stereo encoder some-
times depends on the number of subcarriers in use. Some regulatory authorities re-
quire that total baseband peak modulation be maintained within specified limits.
Thus, the level of the stereo main and subchannel must be reduced when a subcar-
rier is turned on. The 8300's remote control feature allows you to reduce the stereo
main and subchannel level by connecting an on/off signal from your subcarrier gen-
erator (See page 2-8). You define the amount of reduction in percent using the pro-
cedure in step 21 on page 2-23. See page 2-36 for information on programming the
remote control.
A jumper on the circuit board can reconfigure the SCA 2 input to provide the stereo
pilot tone only, which can provide a pilot reference for an RDS subcarrier generator.
The Remote Control Interface is a set of eight optically isolated GPI inputs on a DB-
25 connector, which can be activated by 5-12V DC. They can control various func-
tions of the 8300:

Recall any Factory Preset, User Preset, Test Mode state (Bypass or Tone), or exit
from a Test Mode to the previous processing preset.

Switch the stereo encoder to stereo, mono-from-left, mono-from-right, or
ORBAN MODEL 8300