Eory Frank wrote: > If you want to constructively add multiple signals, then the > less directional antenna is superior. It may be that the > "principal ray," if there is one, does not have enough SNR to > meet threshold, so a narrow beamwidth antenna that selects > only this ray does not result in reception. But an omni or > much less directional antenna like a loop can collect energy > from a multitude of different signals, that when > constructively added, exceed the threshold SNR with margin to > spare. These less directional antennas have the added > advantage that they don't need to be re-aimed, or at least > require much less re-aiming, to receive all available broadcasts. Good points. So, what you achieve this way is a much more reliable reception of signals in which (S + I)/N is something like 14.9 dB. And where S/(N + I), the number people usually quote, might start to appear like its approaching or even violating the Shannon limit. This by itself would be wonderful. Reliable reception just about any time (S + I)/N is better than 15 dB, rather than only occasionally. The Shannon limit, which applies to (S + I)/N, 19.39 Mb/s, and a 5.38 MHz channel, is 10.48 dB. So the question now is whether it makes sense to further develop receivers along the lines of my last post, which would come closer to the Shannon limit but will never quite reach 10.48 dB, or whether to go the way of E-VSB. (Of course, "both" is also possible.) E-VSB changes the Shannon limit by reducing the bit rate, and also reduces the practical S/N margin required downwards. If we are aiming to get beyond a practical 11 or 12 dB of (S + I)/N, E-VSB is the only way to go. Mark Schubin makes a good point about creating a more robust audio signal. The way E-VSB has been defined now, this can be done for a very low price. It would more effectively mimic NTSC in a feature that, maybe unintentionally, was very effective. > This sounds like the familiar COFDM "trick" of using > multipath to your advantage. Lynx demonstrated that it was > also possible to do this with 8-VSB. Now perhaps LG is > demonstrating this principle yet again. They are > well-deserving of congratulations, not only for demonstrating > that excellent 8-VSB reception is possible, but for actually > building a real chip that can be used in actual consumer products. Hear hear. 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.