Radar Scrambling

[Tuck]

At 13:33 04/23/97 MST, you wrote:

>Rather than jamming lidar, which the cop would notice
>when his display either went crazy or read zero as you blew
> past him, it'd be smarter to xmit back a signal that was a
>percentage of your true speed. You're going 80 so set the
>knob on your ECM box to 80% and the cop reads 65.

Can't be done.  The way police radar works is by directly measuring the
speed of your vehicle.  It does this by taking advantage of the doppler
shift, which is a shift in frequency from a wave reflecting off a moving
object.  Police laser works by measuring the change in distance to the
target.  This makes it FAR more susceptible to error than radar.  Say for
example the initial strike of the gun is on the windshield and then the
point of aim shifts slightly (during the 1/2 second or so that LIDAR takes
to lock on) to the bumper.  That would add at least six feet on most cars,
which is a couple miles per hour in the time period involved.  They also
always go off about how the beam is only 6 feet wide at 1/4 mile, but as
car and driver pointed out last month when they discussed how LIDAR had
been defeated in New Jersey, that assumes the cop is standing in the middle
of the lane shooting down a straight piece of road.  If there is an offset
then the beam actually takes a cross sectional slice of the lane it is
intersecting, which drastically increases the surface area of the beam to
the point that it could easily broadside two cars at once.  This article is
well worth reading if you live in a state where laser is common because it
provides a lot of excellent background information for preparing an
effective defense, and it was a good refresher for those of us who have
already been following and trying to figure out how to beat LIDAR tickets.


Justin "Tuck" Cordesman
SOLID BRASS-> Attraction is composed of desire and danger.

"The truth is that men who say that they wish to go out with a bang have a
wisdom that their fellows do not.  For they alone understand that when
death takes them, it must be that he has snuck up upon them and struck them
down with a single blow.  If they are left alive and die slowly -
lingering, then they know that they die because they had the chance to
fight death and they have failed.  They know that death has stolen their
will.  This is the greatest shame that a man who lusts for life can know."

	-Tuck (?-), Earth Leader. Lecture to the Huddled Masses, #1 (1997).