Radio AM to FM

Radio AM to FM: September 20, 2002

AM Stereo fans want, well, AM Stereo

While Ibiquity is performing tests to determine exactly what kind of interference their digital broadcasting system would cause to the AM band at night as well as what might be done about it, a small group of AM enthusiasts wants to scrap the whole plan for an idea that has already been declared a failure by most observers.

Numerous posts on the Yahoo Groups AM Stereo Forum have been quick to point out flaws in the AM version of Ibiquity's HD Radio, formerly known as IBOC for In-Band, On-Channel digital, a broadcasting system that places a digital signal inside the analog signal. Regular radios pick up the signal as usual, while HD radios would decode the digital portion and give listeners a near-CD quality listening experience.

At least that's the theory. So far the system has been endorsed only for daytime broadcasts and some on the AM Stereo Forum have expressed doubts that even daytime digital broadcasts would work. Interference is the key, it seems. The digital portion of the signal appears to cause problems with adjacent channels, making stations near on the dial to an HD AM station difficult to receive.

Personally, I'm not too concerned. I think that the HD AM system can be refined enough to make it work, both day and night. But it is interesting to reflect upon the ideas in the forum.

AM broadcasting only sounds bad because of the quality of receivers manufactured since the early 1970s ... very few of them have an AM tuner even close to what was available in the 1950s and 1960s. Most of the few good ones of recent years have been discontinued. Yet until broadcasters voluntarily restricted their bandwidth to an upper frequency of 10 KHz to help reduce interference in the band, AM was actually capable of higher fidelity than FM: While the FM standard calls for a high frequency cutoff of 15 KHz, the old AM standard allowed for 20 KHz. The only problem was interference, both man-made and from nature: FM is almost immune to most types of static, but AM seems to thrive on it. In response, AM broadcasters voluntarily restricted their high frequencies to 10 KHz starting in the late 1980s.

In the past, receiver manufacturers such as Fisher (when it was a US company) spent much time developing AM tuners that sounded fabulous: full and smooth. Nowadays, in order to reduce interference at the lowest possible cost, manufacturers generally design an AM tuner for minimum fidelity, often reaching only telephone quality ... if they even reach that.

What the members of the AM Stereo Forum want is a return to quality receiver design combined with a new push for AM stereo, the broadcast standard that wilted on the vine due to an FCC that thought more of the marketplace than of standards: instead of selecting one out of five submitted stereo broadcast systems, the FCC allowed the marketplace to decide. The marketplace decided it couldn't decide, and by the time the FCC changed its mind and selected a system from Motorola as the standard, it was too late. Eventually music left AM almost entirely and the push for AM Stereo was gone.

With good receiver design and a renewed push for stereo, AM could compete quite well with FM, goes the argument ... better than HD AM.

As I said, I'm not convinced, at least not totally. I've heard recordings of digital AM and they sound great, but I have not heard the interference side effects. One thing is for sure: AM needs help, one way or another. Decent programming would be a start ...

Dave Does News

Dave Williams, formerly of the KABC (790 AM) Dave and Amy morning show, has been hired full time as a staff anchor at KFWB (980 AM). He replaces Ron Kilgore, who left to join the Wall Street Journal Radio Network.

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