tag:blogger.com,1999:blog-25652978.post643714473496635392..comments2023-07-28T08:32:23.662-04:00Comments on SpectrumTalk: MJMhttp://www.blogger.com/profile/07026719682642838870noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-25652978.post-64579799371317273312008-05-05T18:54:00.000-04:002008-05-05T18:54:00.000-04:00As in previous postings, I not only can offer no r...As in previous postings, I not only can offer no rebuttal to your filing, but find myself agreeing with it on whole. However, as in the past, I would like to address a couple of technical points you make.<BR/><BR/>From your FCC filing:<BR/>"The usual wireless microphone in the US uses frequency modulation (FM) technology and frequency division multiple access (FDMA), similar to the first generation of cellular radiotelephones in the early 1980s, except without the cellular architecture and high<BR/>frequency reuse used in the early cellular systems."<BR/><BR/>And<BR/><BR/>"The cellular industry has great experience in frequency reuse and temporary high density venues."<BR/><BR/>A couple of comments here. First, Part 74 BAS users already practice a form of frequency reuse: In different areas of a convention center; in different studios [on different floors] in a TV broadcast complex; among theaters on Broadway; in different areas of a city by ENG crews. This is very much the same type of frequency reuse compared to cellular infrastructure where channels in different sectors of the cell site are reused. In other words, utilizing geographic and antenna rejection isolation. Looking at a TDMA cellular structure where frequencies maybe reused in the same geographic sector means unacceptable latencies in the delivery of real-time audio (or video). Time division by its very nature can't be real time.<BR/><BR/>"For low capacity wireless microphone users (less than 10 microphones),<BR/>SpectraPulseâ„¢ ultra wideband (UWB) wireless microphone Part 15 technology technology is already available from Audio-Technica. (See http://www.audiotechnica.<BR/>com/cms/resource_library/literature/9398c060aadd718a/spectrapulse_brochure.p<BR/>df) While the present model has limited audio frequency range, there is no fundamental limit to extending it."<BR/><BR/>Actually there is, at least in the present. Besides cost to design and build a custom chipset, the increased bandwidth needed to extend the audio range means an increase in latency. Further, 6GHz propagation characteristics are highly problematic (again, at least in the present) for the way wireless mics, intercom, IFBs and IEMs are used. (If the 6GHz spectrum is so great, why don't the WSD proponents seek it?)<BR/><BR/>"In the UK market, Sony is already selling digital wireless microphones (see<BR/>http://www.sonybiz.net/res/attachment/file/95/1193315636495.pdf) that allows a 60% capacity increase."<BR/><BR/>But with 4mS of latency and 125KHz channel steps it's still not a viable solution in all applications, though it is a positive step in the right direction.<BR/><BR/>One last comment on the beacon topic. Whereas I have no doubt a simple stand alone beacon device or more than one, could be deployed in such a manner as to cover the necessary geographic area of a large event site, there are far too many unspecified details concerning the beacon for anyone to simply say "oh, okay. No problem." No one has offered any indication as to how the beacon will operate: Can the user simply plug in a TV channel number or numbers to broadcast as occupied or will the beacon only accept input based on how wireless units to be protected are programmed or on some arbitrary database; will a beacon be needed for each channel; will the beacon in fact be a stand alone device or will it have to be built in to the transmitter or receiver; will it simply be an inexpensive DTV pilot tone generator, or some very expensive and complex transmission that provides a definite pattern the sophisticated algorithm of an Adaptrum type unit will need to determine a legitimate signal? Conceptually, I welcome the beacon - The devil of course is in the details (or the wallets of lobbyists).Anonymousnoreply@blogger.com