[opendtv] Re: 7" ATSC TV
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Sun, 22 Apr 2007 19:01:11 -0400
Dale Kelly wrote:
> * The original ATTC (Blue Rack) test receiver incorporated
> a well-designed double conversion tuner that met those
> expectations.
> * During initial testing, the industry was "blind sided"
> by the poor multi-path performance issue, even though it
> was predicted by a number of engineers.
Since one of the original supposed advantages of 8-VSB was that
real-only equalizers were needed, and that this would reduce cost, I
keep wondering why the receiver designs beginning with 2nd generation
should be made to pay any royalties to LG/Zenith. The real-only concept
has been proven to be flawed, so how come that doesn't invalidate one of
the key receiver design attributes of this Blue Rack gold standard?
If I come up with a radically different way to demod 8-VSB, used by no
one else, do I still have to pay royalties to anyone for my receiver
design?
> * The CE industry, having no where to hide and needing to
> protect it's IP investment and stave off a broadcaster
> revolt, committed significant resources to resolving the
> multipath problem. After a number of false starts laced
> with questionable performance claims and five years time,
> they were able to demonstrate satisfactory performance
> using a Zenith 5th gen.
Since I keep reading that dual-conversion tuners "never" have a tracking
filter in the RF amp, and that single-conversion tuners do, but have the
IM distortion problem, I have to believe that what LG did in their STB
prototype was to add a tracking filter to a dual-conversion tuner
design, or alternatively add some IM image rejection magic to a
single-conversion tuner.
Either combination would solve the IM problem and keep the AGC from
clamping down in the presence of powerful transmitters throughout the
spectrum. I mean, what other part of the LG 5th gen receiver could have
been fiddled with to result in this performance enhancement? The demod
was not, we are told.
But incidentally, I don't believe that this prototype LG box, as opposed
to more available 5th gen LG designs, is necessarily the absolute
minimum acceptable performance for ATSC receivers. Just as I don't
believe that rabbit ear antenna placement exclusively *on top of* NTSC
TVs was an absolute minimum performance requirement for analog
reception. After all, I was never able to achieve that satisfactorally
anywhere I've lived. But that didn't stop me from using analog OTA TV.
(I grant you that the digital cliff makes things a little different.)
It was Linx that demonstrated 8-VSB performance in Rayleigh channels,
which was previously said to be impossible. That probably *is* a minimum
requirement, in practice.
> [The CE industry] are, through their manipulations, largely
> responsible for "the perceived value of an ATSC receiver to most
> consumers being pretty close to $0", which was a self fulfilling
> prophesy based upon their actions, or lack thereof.
I wouldn't pin it only on the CE industry, Dale. There is no correlation
at all between US TV consumers bailing out of OTA TV and the advent of
ATSC. The bail-out started long before 1998, when the transition to
digital OTA started. As of today, I'd say everyone in the US TV business
seems to have interests in keeping OTA TV on a tight leash, as we've
discussed ad nauseam.
Bert
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