[opendtv] Re: Broadband DTV interferers

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Fri, 25 Jan 2008 16:57:27 -0500

Craig Birkmaier wrote:

> Do you think Bert would be willing to pay to help build
> the infrastructure for a service that could deliver 40 or more
> different programs to him in the free and clear?

Yes, I would, because it would be a one-time expense. I object to being
suckered into every Tom, Dick, and Harry's scheme of creating yet
another "infinite revenue stream" for themselves. Certain things one
should only have to pay for at the time of purchase.

(I may not have a rigorous way of defining what these things are, but
radio and TV are in that list.)

But your reponse to Dale is exactly why I wrote my response to Dale.
It's not at all the one-time cost of changing the infrastructure that's
the issue here. It is that your recurring ideas are deeply flawed. If
the infrastructure has to be changed, it had better be for a better one,
not for one that results in recurring problems and high operating and
maintenance costs.

SFNs are tricky, as soon as you place towers further apart than the echo
tolerance allows. It's such a simple stipulation that I don't understand
how you keep forgetting that.

Want a real-world example?

You can use all the fancy models you want, like Longley-Rice, to help
locate your towers. But signals from towers that are way too far apart
*will* in fact interfere, at least some of the time.

Proof? Easy. According to Antennaweb, which uses Longley-Rice, I should
barely be able to receive our local DTT stations, let along Baltimore.
Yet, I receive some Baltimore stations with greater margin than some
local ones.

Try that with large-area SFNs creating supposed cookie-cutter patters,
where frequency is reused between markets. Recurring interference
problems are practically inevitable.

Remember: cell phone networks ARE NOT SFNs.

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