Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!nrl-cmf!cmcl2!brl-adm!brl-smoke!floyd
From: floyd@brl-smoke.ARPA (Floyd C. Wofford)
Newsgroups: sci.electronics
Subject: Re: radar countermeasures
Message-ID: <7386@brl-smoke.ARPA>
Date: 1 Mar 88 14:24:47 GMT
References: <4596@pucc.Princeton.EDU>
Reply-To: floyd@brl.arpa (Floyd C. Wofford)
Organization: Ballistic Research Laboratory
Lines: 77

In article <4596@pucc.Princeton.EDU> you write:

>Think about it: A little black box in your (innocuous looking) Oldsmobuick
>that would, upon receiving a threat signal from smokey, rather than just
>sit there and beep like an idiot telling you to slow down even though its
>already too late, would send back a signal to your friendly Highway
>Patrolman on his X or K or whatever that would register a perfectly
>legal double nickels on the Law's satanic little radar gun's readout.
>Speed with impunity! Drive those Interstates at the speed God made them for!


Good idea!  Yes it could be done.  Not cheaply, it may be prohibitive to the
general consumer.  First have only smooth curves on your vehicle, NO! sharp
edges or corners of any type!  Next cover the entire surface of the vehicle 
with an absorbing material.  Remember a curveacous type in the passenger
seat returns a signal.  Now we do not return any signal to the transmitter,
or have at least reduced its radar cross section to about the size of a
grasshopper (big radar cross section).

Now comes the fun part. We gonna fake him out.  We need to know how he
transmits.  FM-CW or some kind of pulse modulation or maybe some highly
sophisticated spread spectrum scheme.  Probably FM-CW or pulsed, 'cause they
are lots cheaper to make and use.  Nice to know his frequency too, but he
is probably using some off the shelf equipment so i probably can find out
real easily what his modulation scheme and rf is.  Oh yes, are there competing
brands to these devices, that is are the all Radio Shack or Heathkit devices
or are there different brands and models.  Do they all use the same scheme
for reading my doppler shift?  That will make my designing task a lot easier
'cause it will take a different black box to fake out an FM-CW than a pulse
system.  (I really don't know what is used).

OK so far?  Great!  Now he is going to hit me straight on (doppler shift
in radar is related to the range rate).  If i am doing my best x miles
per hour over double nickles, then my doppler shift will show that.  If I
am going y miles above, then my doppler shift will show that.  I am going
to have to vary some parameter in my transmitter in relation to the velocity
of my vehicle so THE MAN will only read double knickles, and always read
double knickles.  Remember if you are the transmitter, THE MAN is moving
with respect to you.  This is an expensive problem you wish to solve, expen-
in the sense that I am going to have to control my device with an input
from some speed indicator from the car.  This hardware will drive up the
cost of my box.

If you are in an F-16 or B1 then the cost of the countermeasure may lend
itself well to the cost of what's being protected.  For the cost of the
speeding ticket and insurance increase I am not so sure you will make
money.

What is neater, cheaper (not cheap though) and more fun is to get yerself
a TWT or equally high powered device and attach it to a real narrow beam
antenna.  Give her a great narrow modulating pulse.  You will fry his front
end or fuse his agc before he knows what hit him.  If you are caught, your
a*s will be reamed.  Consider your license plate useless for public travel,
but what the heck.

My advice at this point is to, instead, buy a Rolls Royce and a chauffeur,
install a cd player, vcr and bar in the back, crank up yer Megadeth, Metallica
or Blood Sucking Pigs cds, put on yer Leave it to Beaver or Rocky & Bullwinkle
tapes, and mellow out with a quart of Jack Daniels.  Your chauffeur will then
be the only one who worries about the speed limit. 

Any government frowns on the use of countermeasures against its law enforcing
agencies.  What you propose is highly illegal.  Governments enjoy monopolies
despite any political rhetoric.  Try printing twenty dollar bills as an
entrepreneurial venture to test my assertion.  They also assert monopolistic
divine providence to use electronic means to detect scofflaws, and legislation
to protect themselves from not being allowed to use their precious equipment.
Jammers, detectors, decoys, masking agents and deceptive devices are probably
illegal in any states.

You do have a good idea.  It is one that has been worked on in the counter-
measure field.  It is both difficult and expensive, both of which are good
reasons to explore the field.  You might make more money if you can come up
with an absorbing paint.


Floyd Wofford
floyd@brl.arpa