[opendtv] Re: Letter to TV Technology
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 9 Oct 2007 18:26:41 -0400
John Shutt wrote:
> Talk about living in the past. Let it go. Actual field
> measurements, which I have shown you numerous times, proved
> there was no measurable real world difference in the fringe.
You have got to be joking. You're talking about some measurements taken
in 1999, and not even those taken by Sinclair, and you're still hanging
onto them as being the Immutable Gospel Truth. Things change.
There have been any number of measurements taken of many different
receivers, by the FCC, CRC, and other organizations, that have confirmed
and reconfirmed the 15-15.2 figure. And I see it at home. And I pointed
out and quoted from Yiyan Wu's paper from 1999, giving the theoretical
basis for these differences.
> There was, however, very measurable difference in multipath
> performance and in angle of acceptance for the receive antenna.
All of that is obsolete. You can't keep ignoring everything that
happened after 1999, John.
First off, the multipath performance of 4th and 5th gen ATSC receivers
is certainly better than that of 2K COFDM with 1/32 GI, which is +/- 7
usec in an 8 MHz channel. So if that mode works okay in the UK DTT
system, and it seems to (they use it in the 16-QAM channels), it must
mean that echo specs of +/- 50 usec or so are adequate.
Angle of acceptance is purely a matter of echo tolerance. That's it.
There have been any number of reports written about 5th gen LG-based
receivers in laptops, showing that reception can be achieved without
moving the antenna. Even Linx tested this out, for their 4th gen
receiver, in field tests. Even Mark Schubin showed this, in purely
Rayleigh channels, and any remaining issues in his site are apparently
with tuner designs, NOT with demod issues.
And again, since you must have missed the main point here, EVERYONE is
going to ther higher powered equalizers these days, in new designs.
That's the bottom line, isn't it? If they were such a bad idea, as
people seemed to think years ago, why did the Chinese go to them, and
why is DVB heading that way too?
Many years ago, I said that the good thing about sticking with 8-VSB was
that because of NECESSITY, we would have to develop equalizer designs to
where reception became robust. And that then we could benefit from the
lower C/N margin this approach offers. So that was the silver lining.
Remember?
Now that we are there, and that everyone else is heading in that
direction as well, you can't continue to come back with refrains from
1999.
Bert
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts:
