[opendtv] Re: Digital TV: Brazil to Adopt Anything But the American System
- From: "Albert Manfredi" <bert22306@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sat, 11 Feb 2006 19:56:53 -0500
Ian Mackenzie wrote:
>Doug
>
>Your'e the one who is deluded. You have been blowing this trumpet
>for years and the tune is a little old now. Why don't you admit that
>ATSC is the one out of step with the rest of the world.
Just like NTSC was, and is. Come guys, let's not fight.
Doug is right to argue that ATSC does not mandate use of outdoor antennas,
any more than DVB-T does. John Shutt keeps referring to the antenna mounted
on a 30' mast as if that were a requirement for ATSC. It might have been
used as a planning factor, but once again, "compared to what"? We should
always ask compared to what?
John and other might be surprised to know that the French TNT (televison
numerique terrestre) also uses a 30' mast planning factor (actually 10
meters, but who's quibbling).
Here's a little gem I found:
--------------------------------------------
http://www.csa.fr/pdf/Rapport-GT2-Aspects_Radiofrequence_de_la_TNT.pdf
En France, le CSA a effectué la planification des fréquences en prenant
comme hypothèse l?utilisation des paramètres suivants :
Modulation : 64 QAM
Rendement de code : 2/3
Mode de réception : fixe (canal de transmission de type Rice)
Mode : 8k (6817 porteuses)
Intervalle de garde : 28 μs (Tu/32)
Rapport du groupe CTE-TNT/GT2 « Radiofréquence » doc. GT2-78
Avec ces paramètres, le niveau de champ médian minimal à planifier1 à une
hauteur de 10 m par rapport au sol est de 53 dBμV/m en bande IV et de
57 dBμV/m en bande V.
-----------------------------------------------
So, the planning factors assume 64 QAM, 1/32 guard interval (which means
very short distance between the towers of an urban SFN), Ricean fading
(which is relatively benign), and the power density measured 32.8' above
ground level.
No one should conclude from this that indoor reception is impossible. But
everyone should conclude that if coverage area is calculated on this basis,
then indoor reception will certainly not be guaranteed for everyone in the
market area.
Just like here in the US.
Bert
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