On Tue, Dec 14, 2004 at 08:24:54PM +0800, Jimmy Andrews wrote: | This radio system is missing something very important - immunity to | being shot down by a $50 parkflyer TX that is just around the | corner... Model Avionics had the solution, but it was snapped up by | Horizon / JR. http://www.spektrumrc.com/ Maybe Futaba wanted to | provide a built-in excuse for crashing?
eh? The link you gave points to somebody who appears to be selling R/C equipment that uses the 2.4 gHz band and spread spectrum. Don't get me wrong -- I do certainly believe that spread spectrum IS the answer to a large number of the R/C interference problems (and I've been shouting this from the rooftops for a while now.) But it's not a magic bullet, and these people are doing at least some of it wrong. (But perhaps it's better to do something, even if it's not perfect, than nothing.) 1) The 2.4 gHz band is one of the noisiest bands out there. WiFi, cordless phones, video transmitters, Wireless ISPs, BPL access points (yes, the last few hundred feet of BPL Internet access is often done via WiFi), hams, leaky microwave ovens -- there's so many forms of interference here that it's not even funny. Yes, spread spectrum does tend to work even in noisy environments, especially if the noise is from other spread spectrum applications. However, many of the forms of interference I mentioned are not or are often not spread spectrum. Consider how well your WiFi works in your house with the microwave on, or while you're using your non spread spectrum 2.4 gHz cordless phone -- this could happen to your plane too. 2) The power limits on the 2.4 gHz band under the part 15 rules (which is what this equipment would fall under) are only like 250 mW or so. That's probably enough -- barely -- but wouldn't give you much extra range. With a big plane and good eyes, you could probably fly your plane out of range and still see it well enough to fly it. (of course, any noise would reduce this range further.) 3) If you're an AMA member, you've basically already agreed to fly using only the bands that the AMA has OK'd. This isn't really a big deal, but if there's an accident, they could easily use this as an excuse not to pay your claim. What we really need is 0.5 mHz or so of spectrum *dedicated* to spread spectrum R/C use (land + air, no need to seperate bands), and allowing about one watt of transmitted power. Unfortunately, we can't use the existing R/C bands, because it would interfere ith them (and the FCC regulations wouldn't permit spread spectrum there anyways), so it needs to be a new band. And since spectrum is money, it might be very hard to get. But once gotten, a standard could be drawn up (so all equipment works together) the AMA could approve it's use, and people could start making equipment to use it, and it would be wonderful -- frequency pins would be for those still using the old equipment. And people would come together in harmony, and peace would reign, people would love one another ... But doing spread spectrum on 900 mHz and 2.4 gHz (and 5.8 gHz, for that matter) for R/C plane use is pretty sketchy. People have done it, and it works, but it's a bit risky. I imagine it's fine on a car where you're never more than a few hundred feet away, but I wouldn't trust it on a plane that you might fly half a mile away. I'd really hate to lose my plane because somebody decided to reheat a burrito. Futaba does know how to make spread spectrum R/C -- most of their industrial R/C systems seem to use it already. But they can't go and do it for our R/C uses, not yet. Smaller manufacturers certainly could, and there are several options out there already, but they're going to suffer from the problems I've mentioned. But boy would it be nice if they could do it ... As for the 14MZ, `blue screens of death' are not really a big danger. WinCE is more reliable than the PC Windows, and the hardware is set in stone, so it only has to deal with one specific system, and that can be tested. Also, the 14MZ has two computers in it -- the WinCE computer, and a more standard computer that actually does the stuff you need in flight. WinCE is just used to set the options, and even if it crashed in flight, your plane would keep on flying. The other cpu is probably very similar to what's in the 9C or 9Z and is well tested. As for Multiplex doing everything before that Futaba is now catching up to, well, the 9Z (and other radios by JR and others) has done many of these things for a long time now. I don't think Multiplex was the first to put a synthesizer and a scanner into a radio -- didn't the Tracker II do it before Multiplex did? You don't have to go out and buy something from whomever did it first -- you want to buy something from somebody who did it best. Either way, there's no way I'm spending $2200 on one of these. I'd rather have a Multiplex for half the price, and even that's a bit more than I want to spend. I'll stick with my 9C for now (which is a fine radio by itself, though if I had it to do again, I'd probably get a Hitec Eclipse with a Spectra module for a bit more than half the price of the 9C.) -- Doug McLaren, [EMAIL PROTECTED] Where a calculator on the ENIAC is equpped with 18,000 vaccuum tubes and weighs 30 tons, computers in the future may have only 1,000 vaccuum tubes and perhaps weigh 1 1/2 tons. --Popular Mechanics, March 1949 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.
