I work with the local DTV station consulting on their datacast system 
and asked about this. There is no plan to abandon 2-6 for TV use by 
the FCC. Is is susceptible to RF impulse noise/lighting etc but they 
are more efficient frequencies for transmitter operation. Folklore is 
that as a tornado gets closer noice will increase on the lower 
channels and lightning is easy to detect on the lower channels also.
Between 6 and 7 is FM radio, Air frequencies, VHF fire and Police, 
Ham radio etc.
Above UHF Ch 60 (700 Mhz) will be given back to the FCC in 2009 and 
they are trying to build a national communications system that is 
shared with Public Service and commercial systems as the Post 9/11 
solution (sic). Google 700 Mhz for the latest news.
When the FCC gave the stations the DTV channel, the station had to 
buy a DTV transmitter for the new channel.  Some got a UHF and some a 
VHF channel and money will decide whether they can afford to buy a 
DTV transmitter for their former channel and if they give the new or 
old channel back.  The digital signal can transmit whatever channel 
the station wants to appear on your receiver regardless of frequency 
plus lots of other interesting information and extra channels. Some 
of our stations display the new channel and others display the old 
one on the screen. The concept is that you will set your tuner on 
scan and the receiver will store the channel but you won't actually 
know what channel frequency it is really on.  We have a channel 3 
that is on DTV 50 but my TV shows 3, the PBS station was 15 and is 
DTV 12 and my receiver displays 12 and neither will likely change to 
their old frequency. This can be good for people who are used to the 
original channel number and bad for those that need to know what type 
of antenna to use.


> When the country goes all digital Chan's 2 through six will no 
longer
> be authorized for television use, they will be converted to other
> radio services.  Also some UHF channels (I think the 60's) will be
> dropped even as they dropped 70-83 some years ago. These too will be
> converted to other radio services.
> 
> So that is why 4 and 5 are going to UHF,
> 
> There are, in fact 3 or 4 TV bands
> 
> VHF-Low Chan's 2,3,4,5 and 6  I think there is a break (Chan's are
> normally every six MHz) 
> 
> VHF-HIGH (Chan's 7-13) and UHF, (The rest of them)
> 
> They are going to drop VHF-Low when they go all digital.
>


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