We spend a lot of time talking about the newer technologies being put to use in a radio station, but the fact of the matter is that the vast majority of our listeners still use analog radios to hear us. For that reason it's worthwhile discussing air-chain audio processing - the last device ahead of the transmitter.

Instead of rehashing all the standard features, I want to emphasize what makes the different devices from various manufacturers unique. At the end of this article I'll discuss comparison techniques that you can use to help decide which processor makes the most sense for your station. You can't base your decision on price and features alone - how the device sounds over the air should also factor into your decision.

For on-air processing, devices will have these features as standard:
■ Analog and AES inputs
■ Wideband automatic gain control (AGC)
■ Multiband AGC
■ Multiband limiting
■ Clipping
■ Analog and AES outputs
■ Processing presets developed by the equipment designers
■ Full remote access to front panel controls (and often more) via Ethernet

These are the standard features we've come to expect from this sort of device. On-air processors for FM will of course include a stereo generator and composite outputs.

Omnia.11

Omnia.11

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Omnia is one of the most well known audio processing manufacturers, and the Omnia.11 is the current flagship product in a long line of OTA audio processors. In addition to the standard features, it adds the following features (among others):
■ Livewire ins and outs in addition to AES, analog and composite outputs
■ Built-in composite low-pass filter to protect RDS/RBDS and SCA signals
■ Single rear-panel SCA input
■ Parallel processing path for HD, DAB or other lossy-codec streams; has its own final mixer and look-ahead limiting
■ Front panel 10.5" full-color touchscreen GUI
■ Embedded Web-browser for remote access
■ Up to 20 seconds of built-in diversity delay
■ 4RU

Of course probably the most interesting feature of the Omnia.11 is its single sideband suppressed-carrier stereo generator capability (SSBSC). When using this feature, only the lower sidebands (of the suppressed 38kHz carrier) are in composite output. The level of those sidebands in the composite output is increased by 6dB (versus the level of the same sidebands, were the double sideband-suppressed carrier used) so that the overall modulation level stays the same. Your station will need to send an informal letter to the Commission requesting experimental authorization regarding use of SSBSC.

If you don't want to pay for extra features, there is a non-HD version of the Omnia.11 available as well.

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