Stand-Alone Stereo Encoder Operation - Orban OPTIMOD-FM 5500 Operation Manual

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INTRODUCTION

Stand-Alone Stereo Encoder Operation


OPTIMOD-FM's software can be upgraded by running Orban-supplied
downloadable upgrade software on a PC. The upgrade can occur remotely
through the 5500's Ethernet port or serial port (connected to an external mo-
dem), or locally (by connecting a Windows® computer to the 5500's serial port
through the supplied null modem cable).

The sample rate is 64 kHz and multiples thereof, up to 512 kHz. The inter-
nal audio bandwidth is high enough to prevent overshoot caused by spectral
truncation of the left/right input signals that are band-limited to 18 kHz or
lower.

15, 16, or 17 kHz linear-phase lowpass filtering can be applied to the input
signal. To minimize input/output delay, this filter can be bypassed, which is ap-
propriate if the input signal is correctly band-limited by the audio processor driv-
ing the 5500.

A left/right domain overshoot limiter is available. This combines look-ahead
and band-limited clipping techniques to control STL-induced overshoots while
minimizing artifacts.

A dual-mode composite limiter is available. It can operate in either "Half-
Cosine Interpolation" mode or conventional hard clipper mode. The "Half-
Cosine" mode provides better separation and preservation of stereo imaging,
while the "Hard" mode provides brighter sound because it creates waveforms
that are closer to square waves. Both modes provide excellent spectral protec-
tion of the pilot tone and subcarrier regions. To ensure accurate peak control,
the limiter operates at 512 kHz sample rate.

A high-accuracy ITU412 multiplex power controller is available, with user
control over the multiplex power threshold. This allows you to compensate for
overshoots in the signal path upstream from the 5500, preventing excessive re-
duction of the multiplex power.

The input signal can be flat or pre-emphasized to 50 µs or 75 µs.

The 5500 can apply J.17 de-emphasis to the input signal.

Silence alarm and digital audio fault tally outputs are available.

Versatile remote control is available via RS232 serial, GPI, and Ethernet.

All normal 5500 inputs and outputs are available, including analog and digi-
tal inputs, two composite outputs with independent level controls, and two
subcarrier inputs (one of which can be repurposed to emit a 19 kHz pilot
reference output for RDS/RBDS generators).
ORBAN MODEL 5500