Beyond IBiquity's HD Radio

By Jack Hannold, Guest Contributor

(Note: I am always grateful for the thoughtful comments and emails I get on my various posts. This one I thought was extremely noteworthy so I am presenting it to you today -- Jerry).

“Utilizing HD Radio for additional revenue opportunities other than audio programming is more promising than traditional broadcasting applications.”

That’s how Jerry began his July 20 post under the headline, “Finally, A Good Use for HD Radio.” And he’s right. With competition from MP-3 players and cell phones – and with the kinds of programming the big corporate broadcasters are giving us – the future of radio, digital or analog, looks pretty bleak.

But whether broadcasters are more interested in duplicating their main channel programming in digital or in adding ancillary services unrelated to their main channel content, there’s a more promising technology available than Ibiquity’s, at least for FM stations, and you may never have heard of it.

It’s called FMeXtra, and it’s from a small Silicon Valley firm called Digital Radio Express, Inc.

FMeXtra has five important advantages over HD FM: (1) greater signal coverage area; (2) fewer interference problems; (3) lower initial installation cost; (4) no on-going patent royalty payment for use of the system; and (5) better audio quality. And those first three advantages are clearly the result of the way FMeXtra works.

Instead of HD FM’s two independently generated digital signals, each of which occupies the nearer half of a “first-adjacent” channel (e.g., for 92.3, the first adjacent would be 92.1 and 92.5), FMeXtra uses the part of the bandwidth within the station’s own channel that would normally be used for an analog SCA signal to transmit its digital signal.

(For those who don’t know, SCA on FM works exactly like the second audio program, or SAP, on stereo TV, except that it’s not meant for the general public. It’s usually used for subscription services – or, in the case of public radio, for things like reading services for the blind. That’s why SCA is not a feature on ordinary FM receivers.)

Partly because the HD FM signals are outside a station’s assigned channel, the power of each is limited to one-two hundredth of the power of the host analog FM signal. Because they’re so weak, and thus subject to interference from distant first-adjacent stations even within their host analog signal’s protected coverage area (while the host analog signal is not), HD FM signals are often unusable at distances where analog stereo reception is good.

FMeXtra’s digital signals, by contrast, are usable whenever the combination of signal strength and adjacent and co-channel interference levels make analog stereo FM reception usable. [Note 1.]

The one-time installation cost is lower because the FMeXtra encoder costs around $10,000, and can be installed in almost any modern FM transmitter in less than an hour. No other equipment changes are necessary (and stations with analog SCA’s can switch to one or two mono digital SCA’s, in addition to having two full-fidelity digital channels to duplicate their analog programming in digital sound).

With HD, which feeds three unrelated signals to the transmitting antenna, it’s usually necessary either to replace the high-efficiency “Class C” output stages, if not the entire transmitter, or to use a second, lower-powered transmitter for the digital signals with a combining network to feed all three signals to the antenna – or to use a second antenna for the digital signals. The cost can easily exceed $100,000. There’s no need to do that with FMeXtra, since the digital signal, in engineering terms, is a true subcarrier. It’s an integral part of the FM signal, and requires no special transmitter.

As for on-going patent royalty payments from stations, Ibiquity requires them, based on station revenues (much like ASCAP and BMI copyright royalties on music), but DRE doesn’t. The only patent royalties on FMEXtra are those paid by the equipment manufacturers.

And FMeXtra uses the advanced MPEG-4 accPlus version 2 codec, providing better audio quality than Ibiquity’s proprietary codec. [Note 1.] What’s more, Ibiquity has changed its codec without filing engineering data with the FCC. For that reason, Jonathan Hardis, who represents the National Institute of Technology and Standards on the National Radio Standards Committee, has petitioned the FCC to stop the HD rollout. [Note 2.]

The only thing HD has going for it that FMeXtra doesn’t is a digital AM system. But that system is so bad that it’s arguably more of a minus than a plus. Even some of the most ardent anonymous defenders of HD FM on the radio blogs – most of whom are probably employees of the big corporate broadcasters that, collectively, own a controlling interest in Ibiquity – shy away from defending HD AM.

On AM, the HD system doesn’t just occupy one-half of each first-adjacent channel; it occupies all of both first- and second adjacent channels! And the signals have one-sixteenth the power of the host analog signal, not just one-two hundredth. Major 50-kilowatt stations make background noise on first- and second-adjacent channel stations over 100 miles away during the day. And with nighttime authorization of AM HD, the band will soon be unlistenable after dark.

I recommend Barry McLarnon’s 2006 essay on the utter insanity of HD AM. [Note 3.] If you’re not technically savvy, read it anyway. Just skim over the engineering terms you don’t understand, and read his trenchant analysis of the political machinations that have got the FCC aiding and abetting the NAB’s attempt to foist Ibiquity’s hare-brained technology on us. It’ll tell you every thing you need to know. (And keep in mind that Barry McLernon, as a Canadian, doesn’t have to worry about offending the powers that be in U. S. radio!)


[1] “Road Testing the FMeXtra,” by Tom H. Jones. Radio World, Nov 8, 2006.

[2] “Should IBOC Rollout Be Stopped?” by Leslie Stimson. Radio World, July 25, 2007.

[3] “AM IBOC Power Levels = Mystery: It's Time to Call a Halt to the AM IBOC 'Experiment' and Start Talking Alternatives,” by Barry McLarnon. Radio World, July 19, 2006.

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