[opendtv] Re: Genachowski pitches his upcoming national broadband plan
- From: Albert Manfredi <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Sat, 27 Feb 2010 19:20:21 -0500
Craig Birkmaier wrote:
> Once again you pounce without a clue...
> I was not talking about receive antennas I was
> talking about transmission antennas. It is
> quite easy to set up masks on transmission
> antenna to control coverage.
a) That is also true for big sticks. b) No matter how you try to rationalize
this idea, you will always end up with interference zones between the adjacent
markets, if you try reusing the same frequencies.
What you seem to be missing is that when people tell you "big sticks must be
separated by at least x hundred miles," if they completed their thought, they
would say "in order to avoid interference zones." If you try to use the same
frequency in adjacent markets, even with SFNs, aiming a transmit antenna AT
BEST will only move that interference zone closer or further away from one of
the two markets. It seems pretty obvious, Craig. The interference zone will not
go away. Think about it.
> The coverage contour is important, but not as
> important as the signal levels within that
> contour. With multiple transmitters it is
> possible to provide more uniform signal levels
> and to deal with terrain and building blockage.
> Big sticks do not provide uniform coverage -
> you may need to attenuate the signal if you
> are close to the tower, and you will need to
> deal with coverage areas that have nasty
> multi-path (multiple signal levels).
Different subject, but yes, SFNs create more uniform coverage WHEN you are
inside the pattern. No, they don't change the interference problem between
markets using the same frequencies.
Example. Replace a 150 KW big stick in Baltimore with three 50 KW towers around
the Beltway. Do you think this makes it any easier to use the same frequency in
Philadelphia? Hardly, Craig. Chances are, you will get poorer reception in
distant cities like Elkton, and you will have created a wide interference band
between Elkton and, say, Wilmington DE. Please do ask anyone you trust who
knows these things.
As to nasty multipath, what do you think the separate towers of the SFN create?
SFNs only work when receivers can handle "nasty multipath." SFNs *are* nasty
multipath!
> No one is being denied. There are MANY smaller
> markets that fill in the gaps.
> There are six large markets in the N.E.
> New York -1
> Philadelphia - 4
> Boston - 7
> Washington D.C. - 9
> Baltimore - 27
> Hartford and New Haven, CT - 30
> And a bunch of smaller markets:
> Harrisburg-Lancaster-Lebanon-York, PA - 39
> Providence, RI-New Bedford, MA - 53
> Wilkes Barre-Scranton, PA - 54
> Albany-Schenectady-Troy, NY - 57
> Syracuse, NY - 83
> Salisbury, MD - 144
> Binghamton, NY - 157
> Utica, NY - 170
> Elmira, NY - 176
> And a bunch of stations that are in sub
> markets that lie near major markets:
Yes, and your point is?
How do you think SFNs would change this? The only reason the smaller markets
can exist is that the FCC adjusts ERP and frequency use to prevent
interference. Ditto with SFNs, assuming you keep coverage as wide in the
existing markets. Which is where the 50 percent (or far less) utilization comes
in. Now, *if* you were to change TV broadcasting to regional vs single markets,
*then* I might buy your idea that SFNs would save on spectrum. All those
smaller upstate NY markets, for instance, would not have to exist. But that
also means throwing the "localism" mantra down the toilet.
> The reality is that a properly designed
> transmission network would provide more channels
> per market using less spectrum than today.
If you are trying to aggravate with vague verbiage and mere professions of
faith, the consider yourself having succeeded. I'm staring to think that the
same folks who use the phrase "the reality is" are maybe those who also say
"it's a well-known fact." <g>
Bert
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