[opendtv] Re: Seeing Ghosts on a Single Frequency Network

  • From: "John Shutt" <shuttj@xxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Thu, 10 Feb 2011 17:07:17 -0500

----- Original Message ----- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
If you try this with a SFN, as you seem to prefer, you have to play the MediaFLO game. 30 towers, and very spotty coverage between the markets, outside of the US 1/I-95 corridor. It's a lot of towers and a lot of interference zones. Or you can mitigate that by moving to DVB-T2, but still expect problems perpendicular to the straight line between these cities, or you can invent some 12 MHz version as you suggest. 

Or, try this really simple alternative.
Using 50 KW big sticks, install Ch 7 in Washington, perhaps toward the south, Ch 11 in Baltimore, Ch 7 in Elkton MD, Ch 11 in Philadelphia, Ch 7 in NYC.
Why in the world do you continue to insist that the only possible implementation of an SFN involves scores of low power transmitters, but MFNs can use fewer, farther spaced, high power towers? News flash: MediaFLO used 50 KW ERP transmitters. Not exactly the up to 1 MW ERP allocated to some ATSC broadcasters, but it is the same ERP that we (WKAR-TV) are currently allocated on UHF channel 40.
Your coverage plan would be perfect if the intent were solely to deliver programming to homes. In fact, it IS the current implementation when you take independent station affiliations into consideration. Fixed receivers don't need to dynamically choose one MFN channel over another. They can choose one or the other, and be done with it.
However, the point wasn't to serve fixed receivers, it was to serve mobile receivers and have them not lose coverage as they roamed from zone to zone (no matter how large or small those zones were.)
What's your bitrate efficiency when you are forced to use ATSC-MH with your MFN scheme? 

John




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