Bob Miller wrote: > Most countries don't have mandated receivers for instance. > The US does. All that means is that some TV customers will be surprised when their TVs suddenly quit working. There is no nagic going on here. If analog TV goes off, either you plan ahead by creating transition mechanisms, or you have to deal with more last-minute problems. > In the article Hoffman rights ... > > "Time marches on, technology advances, and today's ATSC > receivers deal with such conditions quite capably. So > capably, in fact, that we are contemplating the possibility > of implementing single frequency network (SFN) television > broadcasting in the United States." > > He seems to be saying that the latest 8-VSB receiver > capability makes possible the contemplation of using SFN's > with 8-VSB. You haven't been paying attention, then, because this has been covered on many occasions. It's true that better receivers help in making SFNs work, but MOSTLY this is true for passively synchronized SFNs. That's why, for example, the CRC demoed their gap fillers working in Ottawa, with the LG 5th gen receivers. These gap fillers depended on receivers with good pre-echo tolerance, and the 4th and 5th gen receivers were the first ones to provide this capability. The innovation that made true SFNs possible with 8-VSB, i.e. more than just gap fillers, is the one we have talked about here for a long time, Bob. It is cheap, effective, transmitter synchronization. It is A/110. Obviously, better receivers will also help, because propagation paths are often quirky. However there never was anything IMPOSSIBLE about SFNs with 8-VSB. In short, that is what the TV Technology article should have emphasized. > DVB-T which was chosen by Hong Kong earlier was replaced > by DTMB after they tested the two BTW. And DTMB uses training sequences and powerful equalizers, and actually dials back the inherent echo tolerance of COFDM. It not only replaces the GI with a training sequence, but it also goes "backwards" from 8K to 4K mode, or even a single carrier mode, further impacting negatively on COFDM's inherent echo tolerance. So it simply brings together all the bags of tricks that have evolved since the early 1990s, to provide a system that is at the same time robust and spectrally efficient. With transmitter synchronization for SFNs, and better equalizers as well as schemes such as A-VSB for the low bitrate streams, 8T-VSB can have its life extended. Which is the only way to go when deploying new systems like this. You don't stop and start from scratch every time someone has a good idea. 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.