Radio AM to FM: September 19, 2003
Ready or Not, Here it Comes
Ibiquity has released the latest version of the software system driving the HD Radio system -- formerly known as in-band, on-channel digital. Most who have heard samples state that the system is much improved over the old version, which sounded worse than analog signals on both AM and FM.
Of course your ears are analog, and digital doesn't necessarily mean better, unless you're in digital marketing. The problems associated with converting analog AM and FM to digital are huge, and include trying to squeeze large amounts of bandwidth into a relatively small, finite channel currently occupied by your favorite station.
The solution has been to compress the signal, using technology similar to that used in creating MP3s and internet audio streaming. Indeed, the complaint many had of the first release for HD radio is that it sounded just like internet audio. Using a slow modem. With a bad connection. The AM system, in particular, uses such a low bit rate that promised audio quality in the digital system turned out to be a broken promise.
Add to that the fact that, even compressed, digital takes up more bandwidth and, especially on AM, interferes so much with adjacent channels that hundreds of stations may be forced off the air, and the digital future doesn't look so rosy.
Yet Ibiquity pushes on, and the newly released software (codecs) are so much improved that the group evaluating the system -- the National Radio Systems Committee -- has started the standards setting process again after suspending it in May due to concerns over poor audio quality.
New York heritage station WOR has samples of the new codecs available at http://www.wor710.com/Engineering/iboc/audio_samples.htm. WOR is one of America's first HD Radio stations, and has been actively working with Ibiquity to test the AM system on the air and try to make it work.
Not to be outdone, a group of engineers and AM fans who believe that HD won't work have put together samples of their own(www.1240keva.com/airchecks and www.geocities.com/kevtronics), using the same song samples as found on the WOR site, and broadcast using the C-Quam analog AM stereo system currently in use across the United States and a handful of other countries. Locally, KNX (1070 AM) and KDIS (1110 AM) can be heard in stereo if you have a compatible radio.
I've heard both samples, and I own a few good AM radios, one of which does receive stereo. I have to agree with the AM stereo group: Analog AM stereo, when done right, does sound better, at least in the samples so far. A lot better. Digital has a sound that is hard to describe, but it has a certain unclearness to the midrange and high end that sounds awful.
Of course, most current analog AM radios sound awful as well, with high ends that cut off at 3 or 5 KHz rather than the 10 KHz that stations broadcast. And there's the rub: analog AM can sound wonderful, but manufacturers would need to stop taking the cheap way out and actually produce a decent AM section. While digital sounds ok, its still not good enough for prime time, and I'm not sure that people will want to pay money to buy radios that still don't sound great.
What's the solution? I wish I knew. More testing on all improvement systems, both on the transmission end and the receiver end must continue. I feel, though, that 2004 will be a make or break year for HD Radio. If Ibiquity doesn't solve the problems soon, HD Radio may end up being an expensive lesson in engineering.
Copyright © 2003 Richard Wagoner and The Copley Press.
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