Orban OPTIMOD-FM 8700, Руководство по эксплуатации

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OPTIMOD-FM DIGITAL INTRODUCTION
1-5

The 8700i’s two subcarrier inputs are mixed with the output of the 8700i’s stereo
encoder before application to the composite output connectors. One input can
be re-jumpered to provide a 19 kHz pilot reference output. Both inputs have in-
ternal level trims to accommodate subcarrier generators with output levels as
low as 220 mV.

A 192 kHz AES3 digital composite output is compatible and interoperable with
the 192 kHz standard being implemented by several transmitter manufacturers.
These implantations use the left audio channel of the AES3 connection to carry
the baseband, but their 96 kHz Nyquist frequency makes them unable to convey
92 kHz SCAs without aliasing. Orban’s implementation extends the standard by
using the right audio channel of the link to provide bandwidth extension that
accommodates the full 0-99 kHz baseband when used with hardware designed
to use this extra information.

Two digitized SCA inputs can be summed into the digital composite output.
These inputs are not mixed into the analog composite outputs. If you
need to use both analog and digital composite outputs, you must use a Y
connection to split the output of your subcarrier generators so that each
generator output drives one digitized SCA input and one non-digitized
SCA input.

Wordclock/10 MHz Sync Reference Input (called REF IN on the rear panel) can be
used to lock the stereo pilot tone and the digital composite sample rate to a
high precision external reference like a GPS-based frequency standard. This facil-
itates using the 8700i in single-frequency network applications.

Two Dedicated Ethernet connectors for Dante Audio-Over-IP (AES 67 compatible).
Supports Dante Redundancy.

Relay Bypass is provided for the analog, AES3 digital, and composite connections.

The 8700i precisely controls the audio bandwidth of its analog FM processing to
16.5 kHz. This prevents significant overshoots in uncompressed digital links op-
erating at a 44.1 kHz-sample rate or higher and prevents interference to the pi-
lot tone and RDS (or RBDS) subcarrier. The bandwidth of the 8700i’s digital radio
output is adjustable in 1 kHz increments between 15 kHz and 20 kHz.

The 8700i has a defeatable multiplex power limiter that controls the multiplex
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 8700i-processed signal. 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 clip-
ping to achieve a certain sound, the MPX power controller can be configured to
reduce gain after the clippers.