[opendtv] Re: 20060912 Twang's Tuesday Tribune (Mark's Monday Memo)
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 15 Sep 2006 18:12:50 -0400
John Shutt wrote:
> I guess we have to disagree on whether 2 dB is a practical
> difference in the field. Obviously in a static path such as
> a direct wire connection, or alternately a microwave path,
> it is.
>
> In free air UHF broadcasting, 2 dB is nothing, and not
> noticeable.
What Sinclair said was that the THEORETICAL difference is 4 dB. Do you
still think that's insignificant?
Furthermore, that the actual measured difference between the receivers
was 3.28 dB, with instrument testing. Is that insignificant?
And finally that when these 1st gen receivers were tested in the real
world, there was only a 2 dB difference.
Even if I agreed that 2 dB isn't huge, it would be nice to see whether
we're closer to 3 or 4 dB now, with the best of both 8-VSB and COFDM.
I'm not stuck in believing that 1999 field results are the best we'll
ever see. I have every reason to believe that we should be getting
closer to the theoretical difference. Which is not negligible, although
I agree it is still qualified by the extent of multipath. (But much less
so than back then.)
Also as an aside, from my own observations with the Accurian and Digital
Stream STBs, the 15 dB C/N threshold is quite repeatable and
predictable. If there's any slop there it's within less than 1 dB range.
I have observed this many times, when stations become marginal.
Different stations, different azimuths, different antennas, same
results.
Bert
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