Extend the FM Band

An interesting phenomena has emerged in some of the nations most congested radio markets. Since most United States television stations have gone digital, in a few of the nations most populated and congested regions, New York, Chicago, and Los Angeles, analog stations on channel 6, have gone to a radio format.  Typically broadcasting some video, like old silent movies, all day long, in order to fulfill the Federal Communication Commissions requirement that they broadcast video, they have been using the audio carrier in radio station format, and promoting their stations as FM 87.7, although the carrier is actually at 87.75, the audio carrier frequency for channel 6 television.

This is a less than ideal solution given that 87.75 won’t be tuned in properly by any modern digitally synthesized FM receivers and the modulation index of a television audio carrier is less than FM broadcast resulting in a lower audio signal and lower signal-to-noise ratio. In addition, the stereo system used by television uses a pilot frequency of 15.75 KHz where normal FM radio uses 19 KHz and the result is a normal FM tuner capable of receiving 87.75 KHz will not be able to decode the stereo signal.  None the less, the Chicago station has succeeded in garnering 1.2% of the adult 25-55 audience in spite of these limitations.

These stations have been exempted from having to go digital because of low power status. This may not be continued into 2015.  These stations, which at least in Chicago, have met with significant commercial success, may be forced off-air in 2015.

The entire digital conversion has not gone as our government had hoped.  The hope in congress and the FCC was that in the process of going digital, television stations would vacate their current VHF frequencies and go to UHF channels, freeing up the old VHF spectrum to be auctioned off for billions of dollars.  They didn’t get the bids they expected.  To the best of my knowledge, Google was the only company which bid.

I’m not surprised.  The expected bidders were mobile service providers, the big wireless telephone companies.  The problem, low and high VHF television station frequencies use a long wavelength requiring a long antenna to be efficient at those frequencies. At 100 MHz, which lies in the current FM broadcast band between low and high VHF television stations, a quarter wavelength antenna is 29 inches or 3/4 of a meter.  Even the very high end of the VHF television band is at 216 MHz, still requires 14 inches of antenna.  Not the kind of antenna that is going to fit well into a hand-held smartphone.

Many stations found performance and coverage issues with their new UHF assignments and opted to remain on their existing VHF frequencies, so those frequencies weren’t freed up in all locations although in many they did move.

In Japan, the FM band is 76-90 MHz and the frequency spectrum from 90-108 MHz was used for television channels 1, 2, and 3, 6 MHz wide channels using NTSC (never-the-same-color), same as here.  These were shut down in the conversion to digital in Japan in July of 2011.

Since the demand for more FM station slots exists here in the United States, else people wouldn’t be doing what they’re doing with channel 6 audio, since channels 5-6 are mostly empty and correspond with the Japanese FM band, and since 90-108 MHz is now empty in Japan, and since bids didn’t come for these frequencies indicating that demand other than FM doesn’t really exist for these longer wavelengths, then why not extend the FM band from 76-108 MHz, both in the United States and Japan.  That would allow manufacturers to produce one receiver that would work in both Japan, and the Philippians where 76-90 MHz has been used, and in North America and Europe where 88-108 MHz has been commonly used, while at the same time satisfying demand in congested regions.  There hasn’t been a new frequency allocated in New York since 1985, it’s time.

Some would argue that only new receivers will be able to receive these frequencies, and while true, that was also true when the AM broadcast band was extended up to 1710 KHz from the previous 1600 KHz.
I’m just kicking this idea out there into cyberspace.  I’d love to hear your comments.

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