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3
Section I
INTRODUCTION
MODEL 708 PRODUCT DESCRIPTION
General
Inovonics introduced its first FM-Stereo Generator in 1992. The
original Model 705 was the hallmark of simplicity, and was intended to
answer the more basic of FM radio broadcasting needs.
The Model 708 includes several additional features, and boasts
performance superior to that of its predecessor. Through efficient
manufacturing techniques and automated calibration procedures, the
708 maintains the tradition of a value leader among FM Stereo
Generators.
Features
Features of the Inovonics 708 include:
•
Accurate front-panel metering of the input program,
externally-applied subcarriers, and output signal
levels.
•
Built-in, metered combining for two external (RDS or
SCA) subcarrier sources.
•
Extended-response low-pass filtering with proprietary
overshoot compensation.
•
Digital synthesis of pilot and subcarrier for unexcelled
performance and freedom from drift and routine
adjustment.
•
Built-in, adjustable Composite Processor.
AUDIO PRE-PROCESSING REQUIREMENTS
The Inovonics 708 Stereo Generator incorporates two separate circuits
to safeguard against carrier overmodulation (over-deviation).
Nonetheless, it is anticipate that the 708 will be preceded by some form
of “audio processing” system which places a ceiling on program peaks
with specific allowances for protection of the pre-emphasis
characteristic. It is essential that this need for
split-spectrum
audio
processing be understood and met.
Pre-emphasized
Transmission
FM broadcasting practice imparts a high-frequency
pre-emphasis
(high-end boost) to the input program signal prior to transmission. At
the receiver a complementary
de-emphasis
(high-end rolloff) network
restores overall flat frequency response. The purpose of this exercise is
to reduce the high frequency noise which is invariably added in
transmission. This noise is generally worse for listeners who are some