A very intriguing Petition for Rulemaking was recently filed by the National Association of Broadcasters. It asks the FCC to let the owners of AM stations apply for FM translators, so that they may rebroadcast their AM signals to provide better service, especially at night, when many AM stations must operate at reduced power or go off the air completely. NAB believes the FCC needs to give a much-needed “boost” to the lot of these beleaguered stations.

The FCC has considered and rejected this very notion twice in the last 25 years, but NAB thinks the third time is the charm because of new sources of interference to the AM band. What new sources? Computers and traffic signals are mentioned, but a footnote otherwise plugging digital radio casually drops the comment that AM broadcasters are “encountering ever more interference problems as a result of an increase in ambient noise.”

This is the closest NAB will ever come to admitting that “HD” digital radio makes a racket of the AM dial. That’s because it takes triple the bandwidth to broadcast a hybrid analog/digital AM signal than it does to broadcast in analog alone. Thus AM stations broadcasting in a hybrid mode have the potential to interfere with three times as many other stations. You can see how this makes a mess as the number of AM stations broadcasting in hybrid mode grows.

The more powerful AM stations in the largest markets also happen to be the earliest adopters of digital, so the danger is fairly imminent. The FCC currently prohibits the broadcast of hybrid AM signals at night because of this very problem. When it eventually lifts this prohibition, the static-hash will go national. (The FCC will not consider any changes to digital radio regulations at its August meeting, after pulling a proposal off the July agenda.)

This is a would be quite a boost, all right, in the theft-sense of the word. Allowing AM stations to implement networks of FM translators is a hedge-bet against digital AM signal interference. Not only that, but FM translators can also go digital, which would provide AM broadcasters with coveted access to the side of the digital radio business where the “real money” is expected to be made – on FM. AM broadcasters can’t whine about being left to languish in an ocean of interference if they’re FM broadcasters, too.

Several major amendments would need to be made to the FCC’s FM translator and AM station rules in order to allow this to happen. But if it did, here’s a sketch of the impact. There are 4,759 AM radio stations on the air nationwide. NAB’s proposal seeks to guarantee each AM station enough FM translator coverage to be heard for at least 25 miles. That’s going to take more than one translator station.

By way of comparison, 13,306 new station applications were filed in the 2003 Great Translator Invasion. While a great many fewer than that will ultimately end up on the air, in the NAB’s case you can be damn sure every AM station will apply for every FM translator it can get. It doesn’t take much of a multiple to see the potential influx.

In contrast, just over 1,000 LPFM stations have earned their call letters since 2000, of which 744 are actually on the air.

You don’t fix a fundamentally faulty AM digital radio system design by overrunning the FM band. You fix the faults directly or pursue another design. It’s too bad the FCC doesn’t have the balls to tell that to iBiquity, the proprietors of “HD Radio.” Will it take the NAB’s petition seriously? Two of its listed authors were relatively high-level FCC staff members working issues like these from the other side of the revolving door not very long ago.