[opendtv] Re: 20050810 Wolfsson's Wednesday Words (Mark's Monday Memo)
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 11 Aug 2005 15:38:21 -0400
> - On Thursday, a delegation from Samsung came to my
> apartment to test a new prototype 8-VSB demodulator.
> With a high-gain, directional antenna sitting on the
> inner windowsill and pointing straight across the
> street, we were able reliably and stably to receive
> every signal we could see on a spectrum analyzer,
> which, now that more stations have moved to the CBS
> antenna on the Empire State Building, was more than
> ever before.
> The antenna didn't seem critical. A simple loop
> in roughly the same location also worked. A few feet
> inside the room, however, performance was worse. We
> could get a few stations with the antenna at a set-top
> location but by no means all. A surprise to me was
> that WABC-DT was one of the more difficult, as it had
> previously always been the easiest to receive. It
> may have something to do with the front end of the
> prototype, which was a simple, inexpensive,
> single-conversion tuner. WABC-DT is on channel 45,
> and WNYW-DT is on channel 44. I'd rank this unit
> above those non-LG boxes using the LG 5th-generation
> chip, but not as good as the LG box with the LG
> 5th-generation chip (which could get all but one of
> the stations with a set-top antenna, and the one it
> couldn't get was located in New Jersey). Things are
> certainly improving.
I was wondering whether the 12 manufacturers mentioned
in the NAB and MSTV news clips had new stuff they were
proposing to present in response to the RFQ, and this
seems to indicate that at least some of them do. Good
deal.
This also supports my suspicion that these good but not
super good receivers are hampered by their single
conversion tuners. To me, that is also a positive thing,
because it shows that the really hard nut, the equalizer
design, has indeed reached a satisfactory point. Front
end design, by comparison, is a well known and well
documented art, with improvements readily achievable.
So, very gratifying to see that at least three separate
manufacturers (Samsung, LG, Micronas) now have mastered
the science of equalizers with good, presumably
symmetric, echo tolerance. (I say symmetric because at
the Schubin site, with mostly reflected signal
available, pre-echo must be a major reason for previous
receiver failures, in addition to IM distortion.)
Bert
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