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Nothing Proprietary Here

Stereo MPX over AES answers industry need with standard technology

Frank Foti I read with interest Bob Orban’s comments in “A Full Bandwidth Standard” in the Oct. 16 issue of Radio World Engineering Extra (, keyword Orban).

I compliment Bob for joining us in our efforts to move radio technology forward by very quickly following our lead in implementing Single Sideband Suppressed Carrier (SSBSC) as well as utilizing an AES connection to FM exciters in his products. Mr. Orban recognizes these contributions by our company and has embraced them. We’re glad to see this because it serves radio broadcasters and their efforts to serve their listeners.

Our intent all along has been to explore methods that bring benefit to our industry. The Telos 10, Zephyr and Axia AoIP systems are just a few of our innovations.

Based upon the feedback and results so far with both SSBSC and MPX over AES, it seems that these ideas are working, although clearly there is more to learn! As with any tech rollout, there will always be tweaks. We’ve made major headway in both areas in short order.

Our initial implementation of AES composite method employs a basic sampling rate of 192 kHz. This is by design because we intentionally took an “off-the-shelf” approach that is “standards-based,” which allows exciter manufacturers to implement this tech in months, as opposed to years (again — it’s regular AES). But, we realize that full support of the FM baseband is necessary, so Team Omnia is hard at work creating the next version, which supports 99 kHz spectra. When this work is done, our product will fully support the SCA — in full digital form. Currently, our product is the only popular processor with this capability.

Regarding the use of a standard for MPX connectivity: Together, with Nautel, we realized the AES3 standard will support sampled signals up to 192 kHz. There’s nothing secret, ad hoc or proprietary about this. All we did was route the MPX signal into the AES3 path, and then Nautel routed that signal directly to the modulator stage of the exciter.

This is the digital equivalent of the analog method using an RG-58 cable, with BNC connectors on it. Both are standard methods, as accepted by our industry. The beauty of our choice is we are employing known and accepted standards and methods used the world over. There is no need to further bog down an industry by creating a need to open yet another inquiry regarding what would be the best way to standardize a digital MPX connection. We have one —AES3 — and our joint efforts with the Nautel crew have proven that it works!


If I may say so, the issue regarding a digital method for MPX was first proposed by Omnia back in 1998. If memory serves, I seem to remember a number of white papers written to the contrary of this concept. Interesting how the minds of many have changed!

To date, the MPX over AES tech has been adopted by at least three transmitter companies, an STL company and two processing companies besides Omnia. These are the ones of which we know of! My in-box has inquiries from others who have interest to add the tech, and we’ll follow up with them soon.

Again, we are encouraged that Orban, the other popular audio processor manufacturer is engaged with us in driving the industry forward.

Frank Foti is CEO of The Telos Alliance.

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