[opendtv] Re: Charles Rhodes on SFNs
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 28 Jun 2010 12:20:54 -0400
At 8:07 PM -0400 6/27/10, Albert Manfredi wrote:
Craig Birkmaier wrote:
Richmond to Philadelphia = 202 miles
Washinton to New York City = 211 miles
But none of this is relevant to the current
discussion.
And Baltimore to NYC?
203 miles
Here is a very easy tool to calculate "as the crow flies" distances
using Google Maps:
http://www.daftlogic.com/projects-google-maps-distance-calculator.htm
This is certainly relevant. Because when push comes to shove, what
the FCC does is to assign the SAME channels to every other market,
in congested cases. There are no major markets between Richmond and
DC, Craig, so no matter what, you wouldn't expect them to use the
same VHF channels. And there are no major markets between Wash/Balt
and Phila either. US TV markets are big, and they neeed to be
covered efficiently.
The FCC assigned channels based primarily on distance between markets
initially. Later they had to get more creative and required masks and
power limits to squeeze more channels in.
MOST U.S. markets are considerably smaller than 100-150 mile
diameters, although for some of the major cities in the NE corridor
people do commute up to 100 miles; but they typically live in a
different TV market than the city they commute to.
And in reality, these major markets are actually made up of MANY
sub-markets with the need for more localized services. Where you live
is an interesting example as you are sandwiched between two large
markets with dozens of sub-markets (some with TV stations in-between).
The discussion is bout spectral reuse. With big sticks it is
difficult to reuse a channel inside of 200 miles without terrain
blocking, emission masks, or power limits.
Channel 7 is used in DC, and a low power Channel 7
transmitter also in Phildelphia.
Irrelevant.
Oh, that's truly priceless. The "advantage" of a Ch 7 SFN in the DC
market would be to allow reuse of Ch 7 in at least parts of Phila,
right? Well, that's already done. Just like Ch 13 from Balt and a
low power in Phila. Do you really not get it?
Sure you could keep the current big stick system and re-use channels
for low power in some areas of adjacent markets. As you note, this
already happens, and frankly it is a cheap way to sandwich in another
channel, even if it only serves a small geographic area.
The emphasis here is on CHEAP, which is why broadcasters do not want
to build SFNs. IF people were actually using the OTA service, rather
than cable or DBS, they might feel different, and consider building
an OTA infrastructure that would provide the benefits they now derive
through delivering HIGH POWER signals to the MANY sub-markets served
by cable systems.
The distances between antenna sites for SFNs that
use the same channel for different content can be
significantly closer than 100 miles based on power
levels and emission masks.
Huh? An SFN with different content from each tower, guess what, is
not an SFN anymore.
Come on Bert, this was not a "trick" answer. I am not talking about
different content in the same market. I am talking about re-using the
same channel in an adjacent or somewhat separated market. The content
in the two markets would be different. But one could easily imagine
have a few channels on the same towers used for the SFN in a market
that might ONLY serve sub markets. E.g. in the New York market you
might have a few channels unique to Long Island, others for Staten
Island and Northern N.J. and others for White Plains and Eastern
Conneticut.
The entire point being made in this thread is that with SFNs you can
reuse channels at much closer distance intervals than with BIG
STICKS. Even a high school kid can understand this.
Regards
Craig
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