earle@miracl.DEC (Re-entrant list structures alter DNA) (02/14/86)
Simple question, I hope easy answer: I have a vinyl nose mask on my car. It has cloth backing. The way it covers those nose allows almost no metal to be seen while looking straight on the front of the car. There might be a little metal to be seen from the top of the mask to the bottom of the windshield but it isn't very much because the sloping of the roof isn't that great at that point. The car is a Starion so there isn't much of a 'grille' on the front. The vents leading into the engine are two horizontal slots for the width of the car. The opening is fashioned out of plastic not metal. The headlights are retractable and they have covers for them too. Can't see much of the roof either. My question: Is the front of my car 'stealthy' (sorry for the word, but what the h*ll); i.e. will it make a bad reflector for radar signals? George Earle DECVAX!DECWRL!RHEA!OBLIO!EARLE PS: Anyone ever use a radar interference unit? What do you use it for if all the ads say "be carefull in use when near police radar"? -------------------- Please note that this mail message is likely to be incomplete. The sender aborted the transmission. rhea::MAILER-DAEMON --------------------
mat@amdahl.UUCP (Mike Taylor) (02/17/86)
In article <1134@decwrl.DEC.COM>, earle@miracl.DEC (Re-entrant list structures alter DNA) writes: > Simple question, I hope easy answer: > > I have a vinyl nose mask on my car. It has cloth backing. The > way it covers those nose allows almost no metal to be seen while looking > straight on the front of the car. There might be a little metal to be seen > from the top of the mask to the bottom of the windshield but it isn't very > much because the sloping of the roof isn't that great at that point. The > car is a Starion so there isn't much of a 'grille' on the front. The vents > leading into the engine are two horizontal slots for the width of the car. > The opening is fashioned out of plastic not metal. The headlights are > retractable and they have covers for them too. Can't see much of the roof > either. > > My question: Is the front of my car 'stealthy' (sorry for the word, > but what the h*ll); i.e. will it make a bad reflector for radar signals? Almost certainly, the nose mask will make no difference. Neither will the other plastic/non-metallic parts. The primary radar reflections come from metal structures that resonate with the radar frequency (i.e. 1/4 wave, etc.) These may be located almost anywhere. If non-metallic structures helped, all those Corvette drivers would be getting away with speeding. Sorry, 'taint so. Careful analysis of the metal structures would help, as would radar-absorbent coatings. I think you can actually buy a radar-absorbent "bra," but its effect could be totally nullified by, say, a radiator bracket that was just the right length. -- Mike Taylor ...!{ihnp4,hplabs,amd,sun}!amdahl!mat [ This may not reflect my opinion, let alone anyone else's. ]
bl@hplabsb.UUCP (Bruce T. Lowerre) (02/22/86)
> > > Simple question, I hope easy answer: > > I have a vinyl nose mask on my car. It has cloth backing. The > ... > > My question: Is the front of my car 'stealthy' (sorry for the word, > but what the h*ll); i.e. will it make a bad reflector for radar signals? Most likely, the plastic cover is trasparant to radio waves. Therefore, the answer is no. > PS: Anyone ever use a radar interference unit? What do you use it for if > all the ads say "be carefull in use when near police radar"? I've never heard of this, but from your description it sounds like an ECM (electronic counter measure) device. ECM is used by the military to counter radar and is an active device as opposed to your attempted stealth device which is passive. If this is the case, it would be illegal to use since a radio station license would be required from the FCC which you could not obtain for police frequencies. Also, there are probably laws (state and/or local) pertaining to interference of police activities. Police radar works by measuring the Doppler shift of the reflected signal frequency against the transmitted signal frequency. The simplest method of interference is to "white wash" the radar spectrum with noise so that the reflected signal cannot be detected. In this case, you would be invisible to the radar. A more sophisticated method is to detect (from the vehicle) the transmitted radar signal and re-transmit a strong signal that is frequency shifted down. This will have the effect of fooling the radar unit into thinking that your speed is lower than it actually is. Of course you could also shift the frequency up. This will fool not only the the radar unit but also the cop. He'll take the unit into the shop to be fixed when it reads a speed of 250 MPH in a 35 MPH zone. BTW, I've been told by someone who works in the ECM field that it is possible to make a passive ECM device for police radar by constructing a properly designed antenna/reflector. However, he would not elaborate. I will repeat, such devices are illegal.