[opendtv] Re: Doug is Missing the Point
- From: "Ian Mackenzie" <ian@xxxxxxxxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 17 Feb 2006 09:30:29 +1100
=20
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx]
On Behalf Of Doug McDonald
Sent: Friday, 17 February 2006 5:35 AM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Doug is Missing the Point
Ian Mackenzie wrote:
> Doug
>=20
> You have it wrong as usual.
>=20
> The coverage of Sydney uses a SFN on UHF from Multiple transmission=20
> sites which are fed
>>From the digital transmission on VHF off air.
> No microwaves, no fibres, etc.
>=20
Then it's NOT AN SFN. Well, the UHF part micght or might not be
depending on whether the transmitters are phase-synchronized.
Doug
You just don't understand how a SFN works.
IT IS A SFN
The SFN principle is that you can cover an area with
Multiple transmitters from multiple sites with overlap
From multiple sites at a receiving location so that
There can be multiple "echoes" or even "pre-echoes"
Without affecting receivability.
The proviso is that they are within the guard interval.
In any SFN the transmitters are phase synchronised
It wouldn't be a SFN if they weren't.
FOR A SFN YOU DO NOT NEED TO HAVE A MODULATOR, SFN ADAPTER
GPS REFERENCE, MICROWAVE FEED, (or fibre)TO EACH SITE
AS THE FEED CAN BE OFF AIR.=20
This is what is being commonly done with DVB COFDM in=20
Australia and many other countries.
>=20
> As to transmitter costs the cost for a DVB Transmitter is identical to
> an ATSC transmitter It just uses a different modulator.
>=20
What you describe seems not to be a true SFN and if it
is just off-channel repeaters, it's no different from what
ATSC does trivially.
Not exactly trivially but IT IS A TRUE SFN!
> The nationwide SFN is ridiculous, just like=3D20
> the thought of covering the USA in ATSC.
> In Australia anyone, anywhere can get the=3D20
> networks in digital if not FTA VHF or UHF
> Then on satellite.
>=20
Ah so you DON'T have universal COFDM OTA coverage!
Just what I thought.
Doug, What you may not realise is that in Australia
we have many huge areas where no-one lives and there is a
population of 5 Lizards and 1 Feral cat chasing them=20
per 100 square miles or more.
Do you seriously suggest that there should be 5
"Earth Scorchers" to allow the perhaps 5 people in
the single homestead within range to be able to=20
select which programme they watch?
The populated areas are well served with DVB COFDM
without having to run silly powers.
=20
=20
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