Dale Kelly wrote: > > Craig wrote: >> This is not spectrum set aside for TV use. It is spectrum >> set aside to protect high powered broadcasters who are >> using the same frequency in an adjacent market. This >> is the main reason that the current broadcast TV >> system is SO INEFFICIENT with respect to spectral >> re-use. > > Craig, > This is an academic argument that you circulate with > regularity. Surely you aren't seriously suggesting that we > scrap the billions of dollars invested in the current DTV > transmission system. I don't even think that's strong enough of a counter-argument. What Craig continues to re-forget, with every iteration of this topic, is that in order to cover ubiquitously large, adjacent and contiguous markets, where no excuse exists to introduce dead zones, you have to allow for overlap. And furthermore, you would need a dense mesh of towers to create any semblance of cookie-cutter patterns that he seems to favor so much. No DTT system in the world has gone to such a scheme, and certainly not for FOTA TV. The (viewgraph-engineered) concepts advanced by Qualcomm, for Wash DC to NYC coverage, required a dense mesh of 30 or so towers, for a coverage area that was far smaller than the 4 big sticks provide now. And yet to be demonstrated how changing interference patterns, weather-dependent, would affect even that. What I find ironic is how the 700 MHz spectrum is described as being highly coveted, because of the "vast distances" of coverage that it can provide. That is indeed a nice attribute, but especially for broadcast systems. Much less so by systems that depend on a high level of spectrum re-use, for support of many, many two-way links. The exact quote: "They can transmit across vast distances and through buildings, making them highly sought after by wireless companies." Hmm. Maybe true about "through buildings," but "vast distances?" Even in Berlin, where they started out with the idea of deploying an SFN, they use only two towers, or three for a few of the channels, and the towers are tall, medium-powered sticks, with spectral efficiency reduced to 16-QAM, and wide coverage patterns with uneven boundaries. > "In my most recent experimental studies, I found that > Triplets of Undesired DTV signals which are asymmetrical, > such as channels 30, 32 & 37 produce a broad spectrum of > noise from channel 22 to 45 inclusive. (This will be published > in a "TV TECHNOLOGY" February issue). The point here is > that such signals could be either DTV or from unlicensed > devices or a mix. They all look and act the same. This kind > of super-broadband interference may jam multiple DTV > signals.....". > Here Charlie Rhodes reports on yet another possible source > of the seemingly inexplicable failure of ATSC reception in > many locations. Such interference should be reduce with > the NTSC shutdown but will then increase if unlicensed > devices are authorized in these so called White Spaces. Disturbing. I am actually amazed at how well DTT reception does work with adjacent high-powered NTSC stations, and adjacent DTV stations. So I've been hoping that most of the mysterious problems reported are caused by the high-powered NTSC, rather than DTV stations. This kind of introduces some more doubt. (BTW, isn't Ch 37 tabboo?) Bert _________________________________________________________________ Need to know the score, the latest news, or you need your Hotmail®-get your "fix". http://www.msnmobilefix.com/Default.aspx ---------------------------------------------------------------------- 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.