[opendtv] Re: Another vote against ATSC
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 7 Jan 2009 12:03:25 -0500
Cliff, I did grasp the significance of those quotation marks.
Craig Birkmaier wrote:
> Sensible power levels should be about 10 to 100 KW from a
> network of transmitters serving each market.
I know that Craig gets stuck on his points of view, no matter what evidence is
presented over any number of years. But let's go back to the recent Doug Lung
column on the 2008 IEEE Broadcast Symposium, which I posted last month:
http://www.tvtechnology.com/article/70966
To assist those who didn't read it, I'll get right to the part that addreses
this:
"The 'Statistical Analysis of Digital Television Planning for the ISDTV System'
by Késia C. Santos, Erik F. Silva and Marcelo S. Alencar compares a single
stick transmission facility with three variations of a single frequency network
using multiple lower power transmitters. The study used a 3D ray tracing method
to calculate field strength and power data in a 2.4 km by 3.4 km urban area.
Three antennas at 60 meters with a power of 5 kW each resulted in an outage
probability of 5.5 percent (94.5 percent coverage). Five antennas at 45m, with
a power of 3 kW each, provided an outage probability of 5.8 percent. Using a
single tower at 100 meters with 5 kW provided only 81.2 percent coverage. It
was necessary to increase the transmitter power to 30 kW to reduce the outage
probability to 5.3 percent (94.7 percent coverage)."
So, let's lay this out.
No. of sticks Power each Coverage
------------- ---------- --------
1 at 100 m 30 KW 94.7 %
3 at 60 m 5 KW 94.5 %
5 at 45 m 3 KW 94.2 %
Moral of the story: increasing the number of smaller sticks in the SFN is a
difficult way of providing equivalent, ubiquitous coverage. The best
compromise, IMO, is the big stick assisted by gap fillers, for large area
coverage.
Bert
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