On Fri, Apr 01, 2005 at 07:17:51AM -0000, Dave H. wrote: | This idea of digitally encoding the signal is feasible. I work with | remote controlled industrial cranes and locamotives that operate on | 72MHz. In one area we have 3 cranes operating on the exact same | freq with different digital addresses without any interferance.
Futaba even makes this sort of equipment -- http://www.futaba.com/products/irc/products/telecontrols/index.asp The problems keeping us from all having R/C radio gear like this are political rather than technical -- 1) we can't use the 72 mHz band, because 1) I don't think the FCC regulations would permit spread spectrum anyways, and 2) it would (or could) interfere with the existing radio equipment. I've seen arguments that spread spectrum allows you to use existing spectrum and not interfere with it. This may be true to some degree, but the first time a plane crashed with old style equipment and they thought it was interference, who do you think they'd blame? 2) the existing unlicensed bands (900 mHz, 2.4 gHz, 5.8 gHz) would work, but there's already so much noise there (especially in 2.4 gHz) that we could easily run into situations where we couldn't control our planes. That, and the power limits are so low that we couldn't get much range. 3) we're not likely to get a new band unless we give the FCC a few million dollars. Spectrum is big bucks. 4) and the AMA rules specifically say which bands you can use, and it's limited to the standard R/C bands. (and not following their rules can be a problem in some cases. Especially since by joining you did agree to follow them.) Probably the best thing that could be done right now would be to have a ham make equipment that works in the 53 mHz band -- it's OK for R/C use by the AMA, allocated for R/C use by the ham band plans (at least in the US), and ham radio rules permit the use of a full watt for R/C and for spread spectrum use, so the range would be as good as we're used to. It's also lightly used and the spread spectrum would ignore any narrow signals unless they're incredibly strong. Of course, the downsides are that 1) only hams could use it (but the tech test is easy), and 2) being 50 mHz, the antennas would still be long -- 1.5 meters or so, not counting a matching network -- not short like the higher frequencies would let us use. I don't really have the resources to set up something like that, but if somebody else did, I'd probably buy it. Hint hint :) -- Doug McLaren, [EMAIL PROTECTED], AD5RH Never underestimate the Power of The Dark Side. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
