Radar Scrambling

[John Hess]

Actually, it is my understanding that the Phantom "Chirps".  In ECM 
parlance, this means that it returns a rapidly phase shifting signal. 
 A Doppler radar, such as the police use sees this as a rapid speed 
variation and refuses to display it.  As you stated, the jammer 
becomes ineffective when the proximity of the car to the radar is such 
that the radar reflection is greater than the direct radiation of the 
jammer.



----------
From:  Walters Chris[SMTP:p23610 at gegpo6.geg.mot.com]
Sent:  Wednesday, April 23, 1997 5:50 PM
To:  'diy_efi list'
Subject:  Re: Radar Scrambling


>~Car and driver ran a test of a laser jammer a few months ago that 
used its
>~own laser instead of a bunch of IR LED's.  On a black firebird with 
no
>~front plate the thing effectively rendered the car invisible to 
laser.  Of
>~course their tests of passive jammers have always shown that they 
never
>~work.  One of the funniest tests I saw of those things was when they 
put a
>~whole bunch of them, like a dozen or so, on the dash of some car and 
drove
>~it at the radar gun and it didn't do a damn thing.
>
>I'll add my anecdotal evidence to this:  I got the "Phazer" unit 
(first
>checking that the outfit has a 90 moneyback return policy) and went 
out
>hunting those RADAR machines that display your speed. (Note: the 
"Phazer"
>is the scrambler part of the detector/scrambler sold as the 
"Phantom".)
>
>Results : arguable.
>
>* The instructions (not the sales pitch) mention a 100' 
"punch-through"
>  range.
>
>* The display post happily displayed my correct (and legal) speed 
BUT
>  it did not turn on until ~100'.

Ah, this means the Phantom can 'cloak' you to within 100' of the radar 
unit.
Pretty good, plenty of time to slow down. I'll bet it transmits the 
radar's
signal back **inverted** thus causing the radar's detector to get no 
input.
Reflected positive signal  + xmitted negative signal = no signal. Your 
cloak
 drops when the power of the xmitted negative signal becomes less 
than
the reflected positive signal.

The next level  would be for the Phantom to automatically match the 
power
of the positive signal -- you'd then be invisible right as you passed 
by. Cool,
except the cop is going to know something screwy is going on when all 
the
cars behind you register just fine. So you'd be best served with the 
Phantom
sending out a percentage of your true speed.


Snake (Mr. Electronic Counter-Measures)
TWO pretty cool Fords, one very cool Dodge