[opendtv] Broadband DTV interferers

  • From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
  • To: "OPENDTV" <opendtv@xxxxxxxxxxxxx>
  • Date: Thu, 24 Jan 2008 13:29:15 -0800

Craig wrote:
> This is not spectrum set aside for TV use. It is spectrum set aside to
protect high powered broadcasters who are using the same frequency in an
adjacent market. This is the main reason that the current broadcast TV
system is SO INEFFICIENT with respect to spectral re-use.<

This is an academic argument that you circulate with regularity. Surely you
aren't seriously suggesting that we scrap the billions of dollars invested
in the current DTV transmission system. Would the potential recipients of
this freed up spectrum be willing to fund the enormous amount of
construction required to implement such a change? 

Also, you should learn more about the FCC allocation process. Many UHF
channels can not be utilized within a market simply because they are
"Taboos" that can create harmful IM interference to other stations within
that market. One simply can not use "intuitive" arguments regarding channel
assignments; there are physical axioms which must be taken into account.
Consider this:

"In my most recent experimental studies, I found that Triplets of Undesired
DTV signals which are asymmetrical, such as channels 30, 32 & 37 produce a
broad spectrum of noise from channel 22 to 45 inclusive. (This will be
published in a "TV TECHNOLOGY" February issue). The point here is that such
signals could be either DTV or from unlicensed devices or a mix. They all
look and act the same. This kind of super-broadband interference may jam
multiple DTV signals.....". 
Here Charlie Rhodes reports on yet another possible source of the seemingly
inexplicable failure of ATSC reception in many locations. Such interference
should be reduce with the NTSC shutdown but will then increase if unlicensed
devices are authorized in these so called White Spaces.

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