Orban OPTIMOD-FM 8500S Operating Manual page 31

OPTIMOD-FM DIGITAL
lock its 19 kHz pilot tone and output sample frequency to this input. This is par-
ticularly advantageous in single-frequency network applications.
•
A defeatable diversity delay can delay the FM analog processing output up to
16.2 seconds. Delay can be trimmed in intervals of one sample of 64 kHz to
match the analog and digital paths in the HD Radio system, eliminating the
need to use the delay built into the HD Radio exciter and permitting the
8500S's internal stereo encoder and composite limiter to drive the ana-
log FM exciter. Both the 8500S and 8500S/FM offer this feature, making it con-
venient to use the 8500S/FM in dual-processor HD installations where the digital
channel receives independent processing from a processor like Orban's Optimod-
DAB or Optimod-PC. Each output (Analog, Digital 1, Digital 2, Composite) can be
independently configured to emit the delayed or undelayed signal.
•
The analog inputs are transformerless, balanced 10kΩ instrumentation-
amplifier circuits. The analog outputs are transformerless balanced and float-
ing (with 50Ω impedance) to ensure highest transparency and accurate pulse re-
sponse.
•
The 8500S has two independent composite baseband outputs with digitally
programmable output levels. Robust line drivers enable them to drive 100 feet
of RG-59 coaxial cable without audible performance degradation.
•
The 8500S's two subcarrier inputs are mixed with the output of the 8500S's
stereo encoder before application to the composite output connectors. One in-
put can be re-jumpered to provide a 19 kHz pilot reference output. Both inputs
have internal level trims to accommodate subcarrier generators with output lev-
els as low as 220 mV.
•
The 8500S precisely controls the audio bandwidth of its analog FM process-
ing to 16.5 kHz. This prevents significant overshoots in uncompressed digital
links operating at a 44.1 kHz-sample rate or higher and prevents interference to
the pilot tone and RDS (or RBDS) subcarrier. The bandwidth of the 8500S's digi-
tal radio output is adjustable in 1 kHz increments between 15 kHz and 20 kHz.
•
The 8500S has a defeatable multiplex power limiter that controls the multi-
plex power to ITU-R BS412 standards. An adjustable threshold allows a station to
achieve maximum legal multiplex power even if the downstream transmission
system introduces peak overshoots into the 8500S-processed signal. Because this
limiter closes a feedback loop around the audio processing, it allows the user to
adjust the processor's subjective setup controls freely without violating
BS412 limits, regardless of program material. The multiplex power limiter acts on
all outputs (not just the composite output). In its most common configuration, it
reduces clipper drive when it reduces power, simultaneously reducing clipping
distortion. However, to accommodate customers who wish to use heavier
clipping to achieve a certain sound, the MPX power controller can be con-
figured to reduce gain after the clippers.
1-5
INTRODUCTION