I know at one time they had these things. But now I can’t find them listed anywhere on the ‘net.
Did they become illegal? If not, or only in some states, how effective are they? Anyone had an experience using one? Can, like I’ve heard, set the thing for any speed I want and then have it come up on the officers gun as the ‘speed’ I’m traveling at?
It might be possible but I doubt such a device in production fakes a particular speed, just sends garbage to mask the original signal. I think to fake a speed, you would have to have it wired into your speedometer to calculate exactly how to fake a doppler shift to adjust your actual speed to the desired apparent speed, plus send out a signal that is 180 degrees out of phase with the signal being bounced back by the actual radar so it cancels it out. Or something like that.
This may be illegal just about everywhere because it would require a device that technically broadcasts on a police frequency, which is generally illegal for civilians.
(I think at least some states even prohibit a receiver for police frequencies to be in a vehicle. That is an argument unsuccessfully made in attempts to outlaw radar detectors in some states, although they are illegal in DC and VA, and were illegal in CT at one time, not sure about now.)
I actually bought one of these out of the back of Car and Driver, I believe. This was back in the late 80’s - it had a dial on the front that you set to whatever speed you wanted the radar to say you were going, and it would supposedly jam the radar signal. One funny thing was in the ad the picture of it had the dial set to “55”, and in huge letters was the disclaimer: “Warning: not to be used on police radar.”
Anyway, it completely did not work - I got pulled over once where my radar detector went crazy b/c of Instant On, and I continued to speed, thinking I was jamming his radar. Nope, got pulled over, got a ticket, with the speed listed as exactly what I was driving. The jammer was in plain sight, and the cop didn’t say anything about it.
One other side effect was that it set off everybody else’s radar detectors as you were driving along, which was amusing to watch for the oncoming traffic, but not so amusing when everyone around you suddenly slowed down, creating an instant traffic jam around you.
This is a bit different but I seem to remember someone once selling a stealth bar (the thing you usually put on the fron of a car to prevent nicks in the paint from rocks kicked up from other vehicles). Supposedly the bra was made out of the radar absorbing material. Instead of the signal getting refelected back to the police car it just got absorbed. I have no idea if it actually worked or not (for one thing it did nothing to prevent reflections off of your windshield or the front edge of your roof).
Err…that should have read “stealth bra”.
If you want to get serious about defeating police radar try a chaff deployment system (like they use on airplanes). Of course then they could bust you for littering. 
I remember seeing the plans for a homemade device that SUPPOSEDLY would interfere with infrared radar. I showed it to a mechanically inclined person who said it COULD work and COULD even damage the radar gun. I never read whether or not the person actually used it.
[mischeviously wonders about the legality of strapping HARMs to car]
Im sure those things are illegal as they may affect radio frequencies.
What about those plastic plates you put on your license plate that deflects the radar signal?
In a word, no. They actually increase the distance that a radar can pick you up, because they act as a large antenna. At least the active jammers do, as opposed to passive devices such as license plate covers. Active jammers are also federally illegal, I believe. I think the link does mention one jammer that actually works, but not on the most prevalent Ka band, only on the outdated K and X bands.
Here’s a review of several supposed jammers that Automobile magazine reviewed back in 1996:
http://www.escortradar.com/jammer.htm
They found that none of them worked as advertised. At best, they would decrease the lock-on range of the radar and laser guns; at worse, they would increase the range. Guess you’ll have to settle with camouflaging your car with asphalt and bright yellow stripes.
IANAC (cop) anymore but I believe the plastic plates were supposed to defeat the laser speed detectors. It might work, IF they aimed only at the license plate. Anywhere else on the vehicle would still reflect the signal back to the source.
hijack I actually sat in the city courtroom, listening in on a speeding case where the defendant claimed he couldn’t have been caught on radar because he had put tinfoil in his hubcaps. No cites, no proof, just the memory of most of the room erupting in laughter. /hijack
On another hijack, has anyone ever heard of putting a lightbulb on your dash to defeat radar? Something about the filament in there causing problems? I had always heard that worked, but I’m not the sort to foolishly waste my time seeking out radar-defeating gimmicks…
I was ready to go on a long rant here, but I’ll spare you all and just state that there is no simple or legal way to defeat police radar. Jammers are in direct violation of FCC regulations. Every consumer device in the US that emits radio frequency radiation is required to have a FCC registration. If you think that the FCC is going to grant a registration for a device whose sole purpose is to disrupt the operation of other registered devices, hang on, I’ve got some ocean-front property in Arizona I’d like to sell you.
If effectively stealthing an existing design was possible, what makes you think the USAF, USN, and USMC wouldn’t already be using it on every tactical aircraft they operate. Stealth does not come in a little box so that you can duct tape it to your hood.
There are lots of ways to increase your chances of getting away with exceeding posted speed limits. Jamming and stealth (in the sense of laser and radar speed detection devices) are not among them.
Dammit all.
Instead of forking over a couple hundred bucks for a unit that’d deliver some peace of mind, I’m gonna have to take out a loan and outfit my car with chaffe delivery systems, HARM’s, and camouflage my car an awfull slate grey and ugly yellow.
Figures.
I don’t know, it still might be worth it, just to stick it to the man.
Thanks all (Sorry about your ticket Dooku. It was a funny story, however).
Somehow I knew these things probably didn’t work. Since I hadn’t seen or heard of them in years, I assumed they either worked so great that they were subsequently banned, or they were bunk and people finally wised up.
Yes, there used to be such devices for sale. And they DID jam police radar. However, their maximum effective range was about 10 feet!
I once saw a design for a radar jammer. I believe it involved using something like a motion detector (ie. from a home security system) and mounting it under the front grill on your car. Then, you give it a LOT of juice. The idea is that it works not unlike a CB radio, if you have a powerful enough CB, you can key up and block all the other signals. Same principle here, you’re just throwing a LOT of signal at the gun. This wouldn’t really work though now days, as the aforementioned motion detectors work primarily on X band. Oh and good luck beating the new laser radar guns…
-Dani
Just as a general, cut-the-bullshit, be-all-end-all here: there is no product on the market that will, in any way, protect you from police radar. The jammers sold by outfits like Rocky Mountain Radar are complete crap…somewhere around here I have an article where they proved they actually IMPROVE the range of the police radar gun! Those license plate “blurrers” (you know, where nobody seems to know exactly WHAT they’re supposed to do) don’t work at all, either. No, the police don’t have to shoot the radar gun at your license plate. And no, these plates won’t make your car invisible to photo radar (another study in the same article proved that the cameras could still easily get the plate number).
I’ve read of exactly ONE working radar jammer. This was produced in the late-70s and early 80s, and was effective–at the time. It was a form of active radar jamming, and its downfall was that it relied on analogue technology; it would have to detect the radar coming in, point a radar…emitter(??) in the correct direction, and begin firing. Once police radar got more sophisticated, there was no way the device could react fast enough.
The articles I’ve read suggested that an active (and thus illegal) radar jammer WOULD be possible, but apparently nobody has built (or at least, marketed) one yet that works. It would need to have a fairly powerful set of digital circuitry in order to be faster than the police radar guns, no mean feat as I understand it.
Bottom line? Get yoursel a high quality radar detector (you can forget about “laser detection”; by the time it goes off, they’ve already got you), it’s the best defense you can take against the evil speeding ticket. That or, you know, driving slowly (but the hell with that!) 
I always thought the lisence plate blurrers would prevent those automated machines that take a picture of your license plate and the speed you where going and mail it to you with your ticket.
Virginia is the only state that doesn’t allow jammers.
If radars are fooled by a little lightbulb on the dash, how do they cope with headlights and taillights??
As for the film on licence plate, the ones I’ve seen are for blocking infrared light, so the IR cameras at automated speed traps cannot record your licence plate number.
Hey, I should install one on my bicycle!