[opendtv] Re: FCC seventh further notice of proposed rule making

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Sun, 29 Oct 2006 19:00:24 -0500

Bob Miller wrote:

>> The ERP of their UHF channels is 20 KW per DTT multiplex,
>> not 3 KW. I know you said "average" without specifying
>> which transmitters, but maybe that was just to give the
>> wrong impression.
>
> As usual you have to suggest I am giving out
> misinformation. Yes I could do the Goggle searches and I
> have done them. It is not misinformation to say that the
> average power level of UK digital transmitters is 3 kW
> because it is true.

There's no magic going on here. The London transmitters for DTT are in
fact 20 KW ERP, and their range, at ~1.8 b/s/Hz, is 50 Km. Just about
what one would expect in the real world at that power. Broadcasters in
the US typically expect much better than 30 mile radius with their
transmitters, and are attempting to do this at 3.3 b/s/Hz.

> They have ONLY 80 transmit sites with some six 8 MHz
> channels per site or some 480 transmitters.

Just do the math.

If a 20 KW ERP transmitter can cover a 50 Km (30 mi) radius, then all
else equal, a 3 KW ERP transmitter can only cover a 19 Km radius. Both
of these ranges are well within line of site, so the relationship should
hold very well.

The land area of the UK is 241,590 sq Km. One 3 KW ERP transmitter tower
covers close to 19 Km in radius, or 1134 sq Km. So ignoring the required
overlap and geographical obstacles and all the real-world
considerations, it would take 213 towers to cover the land mass, not 80.

Bottom line: DTT coverage is not 100 percent yet.

In the US, the land area is 9,158,960 sq Km. So it would take 8076 such
towers to cover the land mass, at that would be at 1.8 b/s/Hz rather
than 3.3 b/s/Hz.

> And I don't suggest anyone us their antiquated 2K DVB-T
> system.

The 2K business does nothing to range. It limits the amount of echo
tolerance only. It does not reduce the max range.

> The magic is that in both these countries digital OTA is a
> success. It is a failure here.

That's what is aggravating about this refrain of yours. This has nothing
to do with modulation. It has much more to do with CULTURE.

Even with PAL, the UK, France, and Italy were far more successful with
OTA TV than the US. Are you going to tell me that the difference was PAL
vs NTSC?

Bert
 
 
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