Thought this might be of some general interest for the list. This came off the
Vette list. Neal has been doing research at the university on radar detectors
and jammers. If your thinking about buying one of those radar jammers read on.
Mike G.
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Reply-To: gallaghe@ecn.purdue.edu (gallaghe), vettes@chiller.compaq.com
Subject: Re: Radar Jammers
We have been testing the two radar jammers that we received from the
marketing company. We have taken them apart and studied the circuits.
Our conclusion so far is that they do not work at all. The only circuitry
inside the devices seems to be an oscillator that makes a humming sound
when a button is pushed and a power supply for the light on the front of
the unit. Our feeling is that the antenna in the device must be at least
25 sq cm in cross sectional area. This means that the current jammers do
not have a sufficient antenna area even if they were designed to do
something.
The radar commercial jammers do not work in any of our road test.
The jammer idea that we had does seem to work, but we have used an oversize
antenna; one that is too large for general use. We need do redesign with
a smaller antenna and see if it still works.
About laser radar---I have now purchased and tested a Cincinnati Microwave
laser detector and it seems to work. I have encounterd police laser radar
several times in the past week. It does not detect the direct laser beam
itself, but detects the scattered light. Because the laser radar works
by sending pulses. It measures the distance to the target at each pulse
and computes the change in distance form pulse to pusle. This is how
the the speed is computed. The laser radar detector looks for a pusled
infrared signal in infrared light scattered by dust in the air. It can
give significant advanced warning of a laser radar trap. There are
virtually no false alarms. Unlike a microwave radar jammer, a laser
radar jammer would be very easy to build. It can be active because it
is not against the law to shine a light.
It is still my feeling that the laser radar is easier to detect and defeat
than the microwave radar. Time will tell on this one.
For you interest, NHTSA has put out a call for porposal to evaluate the
effectivness of laser radar. I have a copy of the RFP.
Finally I think it is possible to beat a laser radar ticket. I would use
the followint argument. The coherent laser light and incoherent visible
light diffract differently. The equations that describe the diffraction of
the two types of light are different. Therefore, the target that
the cop sees in his telescope may not be the spot illuminated by the
IR laser.....
Neal
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