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11
SUBCARRIER INPUT
Internal combining is provided for an RDS or an SCA auxiliary
subcarrier. The rear-panel
SUBCARRIER INPUT
connector is an
unbalanced input with a load impedance in the neighborhood of
10K-ohms.
An RDS subcarrier normally accounts for 5% or less of the total
composite multiplex output signal, making it 26dB or more below peak
program modulation. SCA subcarriers typically have a higher injection
level, about 10%, or 20dB below program peak deviation. Subcarrier
inputs ranging in level between –20dBu and 0dBu may be fed to the
SUBCARRIER INPUT
connector, and can be regulated to the proper
injection level by the front-panel
SUB INJ.
level control.
COMPOSITE OUTPUT
The unbalanced
COMPOSITE OUTPUT
of the
DAVID-II
has a resistive
source impedance of 75 ohms. This permits runs of moderate length
(about 50 feet, maximum) to the exciter or microwave link input. If the
cable length is more than just a few feet, the cable, itself, should have a
75-ohm characteristic impedance and be terminated in 75 ohms at the
far end.
A Stereo Generator must always be connected to an exciter or link (STL)
input specifically intended for multiplex stereo. This is a “flat” input,
rather than a monaural program input with signal pre-emphasis.
Program signal pre-emphasis is imparted by the
DAVID-II
.
Output Ground
Loops
Because the Stereo Generator output and the exciter input are both
unbalanced, it is best to locate the
DAVID-II
near the exciter and
power both from a common AC mains circuit. This will help avoid
ground loops and mains-related hum in the transmitted signal.
