🚀 go-pugleaf

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.  ]

> 
> 
> 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.