Thursday, June 25, 2009

The vanishing empire

I remember in my youth TV sets that had a UHF dial that went up to 83.

14-83 were UHF, adjacent 6 MHz channels, starting at 470 MHz. So ((83-14)+1)*6+470 = 890 MHz. And right above that was (and is) the 902-928 Mhz Amateur/ISM band.

So what happened?

Well, the first thing that happened was the creation of the cellular 800 MHz band. That brought the band down to channel 69 - moving the top end of the band down to 800 MHz.

Of course, just under two weeks ago, the band has been reduced down to channel 51 - and now the top end is at 700 MHz. That's 190 MHz that's been reallocated away - almost half of the UHF band.

But even that doesn't tell the whole story. Between channels 14 and 20 are a series of band sharing arrangements that make some of those channels unavailable in certain geographical areas around the country. Here in the San Francisco Bay Area, channels 15-18 are off-limits because 16 and 17 are used in San Francisco for land-mobile.

Low VHF may wind up being the next casualty. It is widely conceded that ATSC doesn't work terribly well on channels 2-6 because of the background noise levels. Can we really justify a nationwide set-aside of 54-72 MHz for the sake of 15 full power TV stations?

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