[opendtv] Re: Continuous performance improvements or not
- From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 25 Feb 2008 16:15:04 -0800
> My second comment is that the noise figure is secondary to all of this,
> no?
Spent last week in the hospital so am getting back to this subject a little
late but then I don't intend belabor the issue in any case. However, I would
say "No" regarding your read of the importance of noise figure (perhaps John
W. can comment on this issue).
Noise figure, as I recall it, is the measure of noise generated within a
receivers circuitry prior to the demodulator and it can/does impact TOV. It
is not difficult to produce a packaged receiver in the 7db NF range but the
typical DTV receiver of a couple of years ago, at least, was in the 12 to
14db range. An engineer from a major receiver design company advised me, at
that time, that we would not be happy with the performance of receivers they
designed to the major TV manufactures spec, which as I recall were generally
A/74 like. Not only was NF high but he also said that selectivity was very
poor.
Dale
> -----Original Message-----
> From: opendtv-bounce@xxxxxxxxxxxxx
> [mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Manfredi, Albert E
> Sent: Sunday, February 17, 2008 3:57 PM
> To: opendtv@xxxxxxxxxxxxx
> Subject: [opendtv] Continuous performance improvements or not
>
>
> Dale Kelly wrote:
>
> > A/74 does not make a recommendation for noise figure and its
> > minimum signal level is much higher than practical. It is not as
> > if these issues were overlooked or misunderstood when developing
> > the A/74 recommendations, this was simply the best that could be
> > achieved by consensus.
>
> Interesting. You're saying that a minimum level of lower than -83 dBm
> could have been receommended. I think we did see levels at least 3 dB
> lower than that in good receiver tests, such as the Samsung Gemini,
> years ago now. So I certainly agree.
>
> One comment is that the lower this sensitivity goes, the worse off
> everyone will be *if* these white space devices ever really come to
> pass.
>
> My second comment is that the noise figure is secondary to all of this,
> no?
>
> If the C/N at TOV is specified to be 15.5 dB, from Table 4.1, and
> sensitivity is specified to -83 dBm, in Para. 4.1, then the only other
> factors involved in computing a noise figure would be thermal noise
> floor and bandwidth of the signal. Since the bandwidth of the signal is
> known (5.38 MHz), then the manufacturer won't have a whole lot of
> latitude. As I see it, the manufacturer can trade off noise figure
> against thermal noise floor, theoretically, and consumers shouldn't care
> that much. To the user, what really matters is sensitivity and C/N
> margin. If manufactuers want to use liquid nitrogen cooling, for
> example, go ahead.
>
> So now the question is, will manufacturers degrade their equipment to
> barely meet A/74? And/or, will the existence of A/74 cause stagnation?
>
> That has been the common wisdom on this list from way back before A/74.
> That manufacturers would put in the worst possible 8-VSB receiver they
> can get away with, just to meet FCC mandates. But this hasn't happened,
> mostly because the chip makers themselves compete. Even the first
> integrated receivers, which came out before A/74, already incorporated
> at least 4th gen receivers, and most of them could easily outperform the
> stand-alone STBs of the day.
>
> A chip maker differentiates himself from the others by offering a better
> performing solution for less money. Moore's law continues to allow this
> to happen. I don't see why this shouldn't continue to happen. I don't
> see why chip makers would NOT compete by touting chip sets that exceed
> A/74, and yet are very cost competitive. Just how much funny business is
> going on in this TV industry, anyway?
>
> The other point is that there are similar organizations to the ATSC,
> such as the IETF and the IEEE, that are run in similar ways. The
> membership of the working groups is service providers, industry, and
> academia. Their standards are also reached by consensus. And yet, the
> vendors always try to differentiate themselves by offering more than the
> minimum. Cisco Systems comes to mind as a perfect example.
>
> 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.
>
>
----------------------------------------------------------------------
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:
