Orban Optimod-FM 8300 Operating Manual page 57

OPTIMOD-FM DIGITAL
Designed to be installed adjacent to each exciter, the CIT25 Composite
Isolation Transformer provides ground loop isolation between the 8300
composite output and the exciter's input, and presents the 8300 with a
balanced, floating load.
Even when its composite limiter is being used heavily, the 8300 will al-
ways protect the stereo pilot tone by at least 60 dB (250Hz from 19 kHz)
and will protect the region from 55 kHz to 100 kHz by at least 75 dB (re
100% modulation).
The subcarrier inputs are provided for convenience in summing subcarriers into
the baseband prior to their presentation to the FM exciter.
The subcarrier inputs will accept any subcarrier (or combinations of sub-
carriers) above 23 kHz. Below 5 kHz, sensitivity rolls off at 6 dB/octave to
suppress hum that might otherwise be introduced into the subcarrier in-
puts, which are unbalanced.
The subcarrier inputs are mixed into the 8300's composite output in the
analog domain, after D/A conversion of the 8300 stereo encoder's output
but before the digitally controlled attenuators that set the composite
output levels.
As shipped from the factory, the second SCA connector emits a stereo pilot tone
reference for RDS or RBDS subcarrier generators. If you wish to reconfigure it to ac-
cept an SCA signal, move the link on jumper J400 (on the I/O board) from pins 3 and
4 to pins 1 and 2.
To access J400, remove the 8300's top cover according to the instructions
in step 1 on page 4-2. To find J400, see page 6-46 for the I/O board parts
Figure 2-3: Separation vs. load capacitance
2-9
INSTALLATION