The Future of AM and FM

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HD Radio's AM Troubles: No Real Solution Ahead

Radio World offers a balanced look at the problems with early full-time AM radio deployment of HD Radio, but it's clear that the solution may be ugly: It's been known for some time that iBiquity's technology for digital AM radio was a compromise the outcome of which was unclear. Since the FCC approved 24-hour-a-day digital AM broadcasting--up from daylight hours only--more knowledge has been gained about precisely how much interference is caused to adjacent and distant stations.

Radio World doesn't conclude digital AM is busted, because, they note, "not enough [AM] stations have been transmitting HD Radio at night to provide a realistic evaluation of the consequences."

However, there's no question there's trouble. The consequence of the FCC intervening where interference is present and requiring stations to back off, or of iBiquity being forced to go back to the drawing board, is digital AM/FM as a whole would suffer a huge blow.

Without AM stations being able to deliver a higher-quality digital signal reliably across their coverage area at night, they're unlike to promote HD Radio much, and their listeners are unlikely to upgrade over time. It's serious enough that, Radio World writes, "Owners like Clear Channel and CBS reportedly are having to choose which AM HD stations to leave on at night and which ones they’ll turn off due to interference inflicted on more important co-owned stations."

If iBiquity is forced by broadcasters or the FCC--the latter being unlikely given the commission's full-on approval--to change AM encoding that would likely mean that all HD Radios sold up until that point would be unable to receive future digital AM transmissions. Radio World notes, correctly, that that wouldn't be a problem if updates could be performed via software. It's possible that the chips deployed so far have that ability and could be flexible enough--although only a few radios have an easy way to handle upgrades. (Some can be upgraded by dealers and manufacturers, I've been told).

But this is not good news.

I've been concerned from the beginning of my coverage of digital AM/FM about the paucity of AM stations broadcasting in HD Radio format. I was told that the lack of 24-hour broadcasting ability was the big reason. But I was also told about the compromises that led to the AM specification being adopted.

The more widely spread the knowledge among consumers (and retailers) that digital AM is up in the air, the less likely receivers will be sold.

Posted by Glenn Fleishman on December 3, 2007 10:35 AM | Permalink