[opendtv] Re: White paper from CEA
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 2 Nov 2005 11:43:51 -0500
Mark Schubin wrote:
> I, too, eagerly await the commercial introduction of
> the one prototype that worked so well in my apartment
> 15 months ago, but not everyone lives in a
> problematic-multipath environment.
I remember you telling me years ago that people from
several organizations had come to your apartment to take
measurements, but that you could not divulge what they
had found. Would have been instructive to see.
Since your rabbit ear OTA reception is 100 percent from
reflected signal, I have to believe that one big problem
with receivers through 3rd generation was their inability
to cope with pre-echo. If the receiver can't handle
pre-echo, it needs a stronger direct path than anything
reflected. Ergo, no reception.
When you reported on the new Samsung receiver initially,
I had not seen the CRC measurements, so I couldn't put
that report in perspective. Now that we see that the
Samsung measures better than the LG (caveat -- the 2003
measurements of the LG, which might not apply), I have to
conclude that in your specific case, further improvements
in echo tolerance might not help. If antenna placement
away from the window doesn't work for the Samsung, when
it did work for LG prototype, then my guess is that IM
distortion products in the tuner are eating into the C/N
margin. So while the C/N margin is exceeded with a window
placement of the antenna, it's not exceeded when the
signal (including multipath) becomes a little weaker away
from the window.
If my guess is right, what I don't comprehend is why
receiver makers don't use the very best front ends in
their initial attempts. And then attempt cutting corners
only after they have done the obvious as well as possible.
Bert
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