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FCC Lets Wireless Devices Use Empty TV Channels
Dr X-ray writes, "The FCC has given its blessing to wireless devices that operate in vacant television channels; unfortunately, the devices can't go on sale until 2009, when all television broadcasters are required to switch to digital transmission. Even then, much of the spectrum won't be available. From the article at Ars Technica: 'Here's how the scheme will work: consumer electronics devices will be allowed to operate in the portion of the TV spectrum being vacated by broadcasters as they switch to digital broadcasts in 2009, with some restrictions. Channel 37 is out — it's used by radio astronomers. Channels 52-69 are also out, since they have been allocated for public safety use. Finally, channels 14-20 might be out (the Commission has asked for more information) because 13 US cities currently use parts of that spectrum for public safety communications.'"
You wouldn't. This would allow for more frequency allocation to wireless devices. Meaning more bandwidth for the rest of us and more channels to prevent channel crossover. Terrible problems in some apartment buildings.
American 802.11g has available bandwidth of 72MHz from Channel 1 to Channel 12. Worst case scenario, thats 3 non-overlapping channels at 54mb/sec each so 162megabits per second.
VHF TV is 12 channels that are 6 MHz each in width, so a total of... you guessed it, 72MHz! So, there is the same amount of bandwidth available in the VHF TV Spectrum with two additional benifits: VHF transmitters are MUCH cheaper than 2.4GHz stuff and also usually can crank out more power, and also VHF passes through walls much better.
The only caravat is that VHF TV spectrum isn't continual. From Channel 6 to Channel 7 is a large gap that fits all the aircraft bands (130Mhz) some pagers (150Mhz) Ham Radio 2M (144MHz) and of course FM Radio (88-108MHz)...
It sounds like their also considering opening up UHF channels, which could in theory offer lots of additional bandwidth even with the restrictions mentioned...
The current TV stations pump an ENORMOUS amount of power into their broadcasts to get that range too. And it's only one way. You'd need just as much power and a huge frickin' antenna to get the signal back to the starting point.
If you could pump similar amounts of power into your wireless router, you'd get some pretty amazing sending range too...
The bottom channels in the UHF TV range are right above the UHF two-way radio allocation that runs from 450 to 470 MHz. That 20 MHz band is used by police, fire, other state/local government stuff, plus commercial users and in many areas they ran out of new frequency allocations.
A bunch of years ago -- 25? -- the FCC allowed users in some metro areas where there were no low-channel UHF stations to extend into the 470 - 512 MHz range to ease congestion. It's commonly known as the "UHF-T" band and it never displaced any existing TV stations. I believe that only public safety users can get licenses for that spectrum.
You mean the FCC mandate that all TVs on sale after March 1, 2007 must support ATSC? And all TVs over 25" being sold right now? Is that soon enough?
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