FreeLists / opendtv / [opendtv] Re: French HDTV trial ERP

["Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>]

Bob Miller wrote:

> Why it isn't easy to receive?

Combination of low power and a C/N margin of 16.5 dB (in gaussian
channel).

Let me out it this way. In Paris, each of the SDTV multiplexes is
transmitted from the Eiffel Tower at 20 KW ERP, as opposed to 840 watts,
and there are three additional 220 W, 500 W, 620 W small sticks to
assist. So, do you expect HDTV to be easier or more difficult to receive
than the other DTT stations?

http://www.csa.fr/pdf/ParisTourEiffel.pdf

http://www.csa.fr/pdf/Paris_Est_Chennevieres.pdf

http://www.csa.fr/pdf/Paris_Nord_Sannois.pdf

http://www.csa.fr/pdf/Paris_Sud_Villebon.pdf


> This document says nothing about problematic reception.

But others, such as Olivier, have commented about that in the past. You
have to be close to the Eiffel Tower to receive the HD multiplex, was
the word.

Reception is probably similar to what our local WDCA-DT was doing,
before it became a MNT affiliate. It seemed only detectable if you were
no more than a handful of miles from the tower.

> If their HAAT was 13 miles all of France could easily
> receive HD with 360 W IMO.

Wrong-o. Let's assume that France is a perfect circle (it looks more
like a pentagon, but they call themselves "hexagon," so circle will be
close enough for now).

Let's completely ignore the antenna HAAT, and just assume magically that
a single transmitter has perfect LOS to the whole land area. So, we'll
use only propagation through free space, omni pattern, radius of the
circle as distance, and 360 W ERP.

The land area of France is 213,010 square miles.

A circle with that much area has a radius of 260.4 miles.

Propagation loss through space, to cover 260.4 miles, would be 140.46
dB.

A centrally located transmitter with omni antenna transmits the signal
at 600 MHz.

The C/N margin required for reception is 16.5 dB, so you can say the
total path loss is 157 dB.

If the transmitter ERP is 360 W, the signal strength at the receiver is
only -101.4 dBm. That's well below any Nordig, and certainly well below
A/74, sensitivity recommendation. Even your typical higher gain yagis
won't bridge that gap.

Bert
 
 
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