[opendtv] Re: COFDM and equalization
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 26 Apr 2004 08:40:31 -0400
At 6:32 AM -0700 4/21/04, Doug McDonald wrote:
>It most certainly is licensed to serve this market,
>Champaign-Decatur-Springfield. Our market is
>long and thin, it's at one end, we are at the
>other. The owners have a station way beyond us,
>even farther at the other end, which would serve
>us better if it were on ... but it is simply
>a mirror of this one, they have absolutely
>identical programming, even the local stuff
>comes from the Springfield end.
>
>In any case, "market" means a different thing out here
>than in the East where you are: out there
>markets are smaller than the Grade B contours
>of stations, here they are much larger ...
>there are substantial areas even in a state
>like Illinois that are essentially unserved by
>analog TV. At full power they will be served
>by ATSC.
Thios is one way to serve these markets, however it is very
inefficient in terms of spectral re-use. The proper way to serve your
market is with several lower powered transmitters distributed
geographically through the long thin market; this provides good RF
thresholds EVERYWHERE in the intended market, with much less
interference into adjacent markets.
The reality is that where you live is "in-between." you are close
enough to other major markets that market-into-market interference is
a real problem. The big stick technique does have merit in
geographically isolated markets like Salt Lake City - but you still
need translators/repeaters to fill in all the gaps.
Even in SLC COFDM still has major advantages...you just have the
luxury of using higher power levels for the main transmitters.
>
>Interference is simply not an issue at all.
>In the absence of tropo, where I live, with
>a reasonable antenna, we get grade A analog signals
>from chs. 3, 12, 15, 17, 23, and 27. There are
>low power ones, none grade B where I live, though
>within 8 miles (!), on 7, 39, 46, and 58. With
>a good antenna you can also get (from the other
>end of the same market) 20 and 55. There are other
>LPs in the market, but they are not visible at all
>except under the most stong of tropo, except for
>occasionally a 29.
>
>There are NO out of market stations visible at
>all analog, period, here, without tropo.
>Not even the slightest hint.
But tropo does exist, and transmitter locations and power levels must
be determined to prevent worst case interference. Hence very poor
spectral efficiency.
>All more power does around here ... and in the west
>in general ... is serve more people.
As stated before, this is an option for ANY transmission system where
market-into-market interference is NOT a problem. If we are going to
continue to protect local markets, then we need to evolve to
transmission networks with better spectral efficiency. Bert will be
quick to point out that this is possible with 8-VSB too.
Regards
Craig
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