Omnia-6ex Use and Operation Manual – V: 1.20
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Chapter-4: Processor Interfacing
This chapter presents installation and operation information specific to the Omnia-6EX. A Parameters Worksheet,
on Page 121, may be photocopied to record the parameter settings used for specific processing presets.
Processor Location
Believe or not, this is an important consideration! Where you choose to locate the processor—at the studio or at the
transmitter—can have a profound impact on the overall performance and your stations' loudness on the dial. We
present a few considerations that will aid in making this decision.
In most applications, installing the processor at the transmitter site provides a solid coupling between the processor
and the FM exciter. Since there is no other transmission link between the processor and the exciter to degrade the
tightly controlled peak output levels, modulation performance and therefore competitive loudness, will be
maximized. The drawback to this setup is that the processor is located in what is usually a remote, acoustically
noisy, and electrically unfriendly environment. Omnia-6EX remote control can be used to make processing changes
from elsewhere.
While numerous options for processor location are provided in the next section, we recommend that Omnia-6EX be
located at the transmitter site for any HD Radio/DAB installation. The key issue that must be considered is that
Omnia-6EX creates two distinctly different processed outputs for the transmitter(s). Unless your STL link is capable
of transporting these signals in a 100% transparent manner, then your best performance will occur when the
processor is located at the transmitting facility.
If you plan to set up the processor at the studio, consideration must be given to these STL factors:
Analog STL Use
• Is the STL path a clean shot? If the path is noisy, or is plagued by fades, multipath, or other types of
interference (especially if a composite STL is used), unwanted noise will be added to your signal, robbing
you of loudness.
• Is the STL a Discrete or Composite system? If a discrete system is used, there must be a provision for a stereo
generator/encoder at the transmitter. In that instance, it is imperative that this stereo generator/encoder not
introduce any distortion or overshoot into the system. Most stand-alone stereo generator/encoders employ
some form of low pass filter and safety clipper. These sections can add significant distortion and modulation
overshoot if not set up properly. If a composite STL is used, the multiplexed output of the Omnia-6EX can be
connected directly to the STL. At the transmitter location, the composite receiver can be directly connected to
the exciter.
• Overshoots: Some analog STL systems, especially those manufactured before 1990, can generate significant
overshoots due to several possible design deficiencies. Subsonic “bounce” can be caused by an AC coupled
modulator/demodulator in the STL system, and this alone can cause 1 - 2 dB of lost loudness. One method of
verifying that a composite STL system is free of overshoots is to connect an oscilloscope to the STL receiver
and monitor the composite waveform, paying special attention to the integrity of the low frequency square
waves. Of particular interest is the “square-ness” of the low frequency waveforms, and whether there is any
noticeable “grass” or “peaky” looking waveforms exceeding the peak level of the low frequency signals. The
top of the low frequency waveforms should look very “flat.” If the top appears to “tilt” in any manner, then
there is a low frequency deficiency in the STL system. (We’d offer further information here on the “how and
why” this occurs, but that could consume a whole chapter by itself!) Simply stated, the problem could be due
