[opendtv] Re: Charles Rhodes on SFNs
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 25 Jun 2010 14:41:27 -0500
Tom Barry wrote:
> How do they typically do it, lay out the areas for frequency use?
> Is a simple black & white checkerboard pattern sufficient? Like:
>
> B W B W B W ...
> W B W B W B ...
> B W B W B W ...
> W B W B W B ...
>
> It seems that would allow half the frequencies but maybe have too
> much overlap at the corners of the checkerboard squares. Or do
> they need something more like the Red/Green/Blue pixel pattern of
> old color tv's.
As you point out, the corners would create problems. But in fact, that does
approximate how it's done.
If the East Coast were nothing but a single line of transmitters, it would be
easy, and 50 percent would be usable. But there are towns like Roanoke VA, SW
of DC, that tend to mess things up.
So you look up Roanoke, and you notice that in fact they use many channels that
are also in use in DC and in Richmond (Channels 20, 22, 26, 30, 39, some low
power, are common to DC and Roanoke, 26, 39, and 42 are used in Richmond and
DC/Annapolis). Probably acceptable because of the Blue Ridge mountains.
Unless we switch to the European model of regional and nationwide broadcasters,
I think we need to stop casually mentioning "SFN" as the silver bullet that
will save gobs of spectrum.
Bert
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