Path: utzoo!attcan!uunet!aplcen!unmvax!ariel.unm.edu!hydra.unm.edu!ee5391aa From: ee5391aa@hydra.unm.edu (Duke McMullan n5gax) Newsgroups: sci.electronics Subject: Re: Fooling Radar Detectors Message-ID: <1990Aug15.112532.17516@ariel.unm.edu> Date: 15 Aug 90 11:25:32 GMT References: Sender: usenet@ariel.unm.edu (USENET News System) Organization: University of New Mexico, Albuquerque Lines: 50 In article fish@gemed.ge.com (Mark Fisher, GE Medical, Milwaukee WI, x4-6553) writes: >Mount 4 or so corner reflectors on a rotating frame such as >a plastic bicycle tire. >Turn the reflectors at a constant rate of something like 120 >RPM. And wa-la your car's dominate doppler shift will be ~ 10 mph >less than you are actually going. ... >The apparent speed of the reflectors will have a sinusoidal modulation >to it from going around in circles. This may prevent the radar from >getting a good lock on the doppler shift and lock in on the steady >doppler shift from the car even though it is dimmer RCS wise. ... >I would hate to get caught with something like this on the top of my >car. :^) Hmmm. Mark, I'd think it would backfire, since the radar will sense the _largest_ doppler shift it finds. In any event, shielding the rest of the car to have a significantly less bright reflection than the reflectors would be a major nuisance. However, I don't _think_ there's anything unlawful about it per. se. Some years back, 73 Magazine ran an article on how an active ECM system for police radar could be constructed around a Gunnplexer. Said article claimed that it was sufficient to AM the uwave carrier at an audio frequency (the frequency being proportional to the speed which the fuzzdar will display). The assertation was that the front end of the fuzzdar receiver is untuned, so the Gunnplexer output would register, even though it's "out of band". They even had a photo of a pair of thumbwheel switches on the dash displaying double nickles. They also had a disclamer to the effect that actually _doing_ this was almost certainly illegal. Sure, it's in a ham band, but it's also deliberate interference with another service, a standard ham no-no. I've thought about building such a thing from time to time, but even aside from cost and illegality, I just don't drive that abusively, and I don't speed that often or that much. My little radar detector (still legal, most places) keeps me out of most trouble on the occasions when I'm an unlawful hurry. 1001001, d -- When you're up to your butt in alligators, it's difficult to remember that the initial objective was to drain the swamp. -- traditional Duke McMullan n5gax nss13429r phon505-255-4642 ee5391aa@hydra.unm.edu