Operating instructions
1-2
INTRODUCTION ORBAN MODEL 9400
Take a little time now to familiarize yourself with OPTIMOD-AM. A small investment
of your time now will yield large dividends in audio quality.
OPTIMOD-AM was designed to deliver a high-quality FM-like sound to the listener's
ear by pre-processing for the limitations of the average car or table radio (while
avoiding audible side effects and compromises in loudness or coverage). Because
such processing can make audible many defects ordinarily lost in the usual sea of
AM mud, it is very important that the source audio be as clean as possible. Orban's
publication Maintaining Audio Quality in the Broadcast Facility (available in .pdf
form from ftp.orban.com
) contains valuable information and specific suggestions for
improving the quality of your audio.
The rest of Section 1 explains how OPTIMOD-AM fits into the AM broadcast facility.
Section 2 explains how to install it and set it up. Section 3 tells how to operate
OPTIMOD-AM. Sections 4 through 6 provide reference information.
For best results, feed OPTIMOD-AM unprocessed audio. No other audio processing is
necessary or desirable.
If you wish to place level protection prior to your studio / transmitter link (STL), use
an Orban studio level control system expressly designed for this purpose. (At the
time of this writing, this is the Orban 8200ST OPTIMOD-Studio Compressor/limiter /
HF Limiter / Clipper.) The 8200ST can be adjusted so that it substitutes for the broad-
band AGC circuitry in OPTIMOD-AM, which is then defeated.
Making the Most of the AM Channel
The 9400 is suitable for long wave, medium wave, and shortwave (HF)
broadcasts.
OPTIMOD-AM rides gain over an adjustable range of up to 25dB, compressing
dynamic range and compensating for operator gain-riding errors and for gain in-
consistencies in automated systems.
OPTIMOD-AM increases the density and loudness of the program mate-
rial by multiband limiting and multiband distortion-canceling clipping, improv-
ing the consistency of the station's sound and increasing loudness and definition
without producing audible side effects.
OPTIMOD-AM precisely controls peak levels to prevent overmodulation.
Asymmetry in the analog processing channel is adjustable from 100% to 150%
positive peak modulation.
OPTIMOD-AM compensates for the high- and low-frequency rolloffs of
typical AM receivers with a fully adjustable program equalizer providing up to
20dB of high-frequency boost (at 5 kHz) without producing the side effects en-
countered in conventional processors. This equalizer can thus produce extreme
pre-emphasis that is appropriate for very narrow-band radios. OPTIMOD-AM's
fully parametric low- and mid-frequency equalizers allow you to tailor your air