[opendtv] Re: FCC comments on DTT reception

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Wed, 14 Dec 2005 18:52:01 -0500

Mark Aitken wrote:

> Among other interesting facets of the OET discussion, the
> graph on page 34 details a large discrepancy in performance
> for a large variety of receivers/tuners/converters based on
> multipath performance. While the focus of discussion in
> this report is whether (or not) coverage assumptions made
> by the FCC are relevant (they argue yes), the body of data
> gathered can paint a picture similar to the focus of many
> previous discussions.
> While it is possible to develop/market/sell DTV
> receivers/tuners/converters that work well (at least some
> prototypes show promise!), there is NO MANDATE that they do
> so, any many fall short!

I think the salient point made, in multipath tolerance as
well as all the other parameters they measured, is that
performance is NOT a function of price. It is instead a
function of "generation." This is something that some of
the vocal list members found ever so hard to accept.

The result of this is that there would be little incentive
for a manufacturer to sell an inferior product, referring to
reception capability. The feature set is what costs money,
not the basics of good RF reception.

So while I generally agree that min performance requirements
are called for, this study might actually suggest they are
not absolutely essential.

I also noted with interest that as selectivity and multipath
tolerance improved, sensitivity and C/N margin required in
gaussian channels became worse -- in the past. Apparently,
the newer receivers do not suffer from this tradeoff. As
was more or less apparent in some informal test results we
saw on this august list. I was worried about this, but no
need to worry, it seems.

I personally disagree with placing too much emphasis on high
gain *directional* antennas as a means of "proving" that
coverage exists, but I understand why certain parties would
want to take that position. I'd like to see some down to
earth, practical comments on this subject by the FCC,
comments which might make sense to people who actually use

Aside from the variability in multipath scenarios, it was
rather heartening to see how very well the bulk of these
receivers measured in the noise, sensitivity, and C/N
margins needed. These are superb numbers, for the most part,
with very a few standouts that were bad.

And, let's not forget, all at 3.3 b/s/Hz! Not having the
crutch of lower spectral efficiency options ain't all bad.
Necessity is the mother of invention.

> The experience of the Broadcast community is that, while
> possible, there is no reasonable expectation that the few
> products put into the hands of Americans today /_will_/
> work in the majority of locations, most of the time, with
> simple antennas.
> If the expectation of Congress is that DTV
> receivers/tuners/converters WILL work for most Americans
> (a requirement to complete an ill-guided transition), it
> is my opinionated suggestion that performance requirements
> be placed on ALL such products, not simply the "digital to
> analog converters" being looked at for subsidy. The future
> ability to reach into American homes with "Over-The-Air"
> television under any circumstances is surely at risk
> otherwise.

I think the basic problem here is the old stuff still being
peddled. You need to belong to a list like this one to know
whether the box you buy is likely to work or likely to fail.

BTW, my brother-in-law in Albuquerque has the new DirecTV
5th gen LG STB and, with an *indoor* antenna, has no trouble
receiving all OTA stations. And he reports a very well
integrated operation, which seamlessly lists OTA and DBS
channels. And he is hard to please.

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