Orban OPTIMOD-FM 8600, Руководство по эксплуатации

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OPTIMOD-FM DIGITAL INTRODUCTION
1-11
de-facto industry standard digital connection being implemented by transmitter
manufacturers and others.
Subcarriers
The stereo encoder has two unbalanced 60
0Ω
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 composite
level control for that output.
The 8600 does not digitize subcarriers appearing at these two inputs; the mixing oc-
curs after D/A conversion and is analog.
Subcarrier inputs sum into the composite baseband outputs before the digitally con-
trolled composite attenuators. The sensitivity of the both SCA inputs are variable
from 220 mV p-p to >10 V p-p to produce 10% injection. Internal PC-board-mounted
trim pots determine the sensitivity.
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 the total baseband peak modulation to be maintained within specified limits.
Thus, the level of the stereo main and subchannel must be reduced when a subcarri-
er is turned on. The 8600’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 2-9). You define the amount of reduction (in units of percent mod-
ulation) on the Input/output screen (See page 2-30). See page 2-60 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.
Digitized Subcarrier Inputs
In MPX hardware, two additional subcarrier inputs are provided on the breakout
cable. These are digitized and are summed only into the digital composite output.
Their mix level is set in the Input/Output 5 screen titled Composite 2. At the PC re-
mote, they are located in the
I/O S
ETUP
S
CREEN
with the tab
D
IGITAL
E
NCODER
.
If you need to use both the digital and analog composite outputs, you must split the
outputs of your SCA generators with Y cables so that each generator output drives
one digitized SCA input and one non-digitized SCA input.
Wordclock/10 MHz Sync Reference Input
The sync reference input (labeled
R
EF
I
N
) appears on a female BNC jack at the end of
the breakout cable that connects to the digital composite connector. It is available
only on MPX hardware. It accepts a 1x 5V p-p squarewave wordclock signal at 32,
44.1, 48, 88.2, or 96 kHz, or a 10 MHz sinewave or squarewave signal, 0.5 to 5 V
peak. 10 MHz is a common output frequency produced by GPS and rubidium fre-