[opendtv] Re: Bolivia TV standard mystery
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 20 Dec 2006 12:22:54 -0500
Craig Birkmaier wrote:
> The problem is not related to the transmission infrastructure.
I'm glad that at least you acknowledge this. Although in that FCC
report, it stated clearly that these nationwide SFNs were an intrinsic
advantage of COFDM. They are not. They are a bear for any system to
implement properly, but in principle (at least) any system can.
> Perhaps this is why you cannot get it through your thick head
> that the infrastructure I am advocating is not only possible,
> but desirable, as it would provide much higher spectral
> efficiency.
Or perhaps it's because when you arm wave, you think you are describing
details. What you claim to describe clearly is internally inconsistent.
> In densely populated areas where markets are closely spaced,
> the infrastructure would rely on a few sticks at relatively low
> HAAT and power, with a larger number of on-channel gap fillers.
And yes, what you describe is what doesn't work.
If you want to cover an entire market area of typical US market size,
without creating large pockets with no reception, these low power and
low HAAT sticks will interfere terribly among each other. Especially so
if they are passive repeaters.
Take a market area of, say, 80 mile diameter, and only small 1 KW towers
to cover it, on one frequency channel. Even with COFDM at 1/4 GI, a
passive system won't work (28 mile spacing max).
So, you say, use fewer and more powerful sticks, all clustered closer
together. Aha, like the Berlin system. And then you lose the sharp
boundary delineation. Get it?
The way to solve that problem is to use a big stick, then use the small
guys as gap fillers. The reason that works is that the repeaters'
signals, if designed correctly, will be swamped by the big stick's
signals when they otherwise would have been interfering with another
small stick. This makes the whole system much easier to build, with no
need for synchronization.
So, why not consult with someone you trust? Someone who understands how
to build these things? I even quoted you from the French TNT technical
report. How is it that none of this phases you?
Bert
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