[opendtv] Re: DVB-T HDTV demo using 19.7 Mbps in a 6 Mhz channel in costa rica
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 6 Mar 2006 11:07:45 -0500
John Shutt wrote:
> The distance reception demonstrations done by Sinclair
> in Baltimore in 1999 showed NO difference in far field
> reception between the two. The theortical 4 dB did not
> show up in practice.
That's simply not true, John. Not even back when the 8-VSB receivers
were so questionable, what with real-only equalizers and all the rest.
Here is the authoritative source, not an anecdotal derivative. This is
from 30 September 1999:
http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/reports/dtvr
eprt.txt
"Sinclair indicates that the purpose of its 'far field,' i.e., beyond 30
miles, testing was to try to determine if a meaningful difference in
performance could be observed due to the differences between 8-VAB and
COFDM in threshold carrier-to-noise (C/N) ratio needed for acquisition
of service. It states that while there is a 4 dB difference in the
theoretical C/N performance between of the two systems in favor of
8-VSB, the average daily calibration threshold difference between the
8-VSB and COFDM receivers was 3.28 dB and that in the field this
difference shrank to 2 dB. Sinclair suggests that this may be due to the
effect of real world impairments that add to the theoretical 'gaussian'
channel values."
Now, indoor reception is no longer a problem, not even with my Digital
Stream box, and dynamic echo tolerance with the better demods is getting
to be quite good. If only these solutions would become readily available
on store shelves.
OTA consumers want the good stuff, and would really love it if
broadcasters would focus on their DTT tier. We don't need to play
footsoldier for different standards lobbies.
Bert
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