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From: fern@polyof.UUCP ( FTG )
Newsgroups: net.auto
Subject: Re: Re: radar detectors and Newark Airport
Message-ID: <175@polyof.UUCP>
Date: Mon, 25-Nov-85 19:12:56 EST
Article-I.D.: polyof.175
Posted: Mon Nov 25 19:12:56 1985
Date-Received: Fri, 29-Nov-85 10:57:10 EST
References: <386@gcc-milo.ARPA> <558@moncol.UUCP> <466@mtunf.UUCP> <631@mtung.UUCP> <567@moncol.UUCP> <633@mtung.UUCP>
Organization: Polytechnic Inst. of NY, Farmingdale
Lines: 35

> In article <567@moncol.UUCP> ben@moncol.UUCP (Bennett
> Broder), in response to a question of mine, treats us to a
> small excerpt from a grade-school physics class, explaining
> how radar guns use the Doppler effect to determine speed.
> Unfortunately, that wasn't the question.
> 
> I'll ask it again: Is the transmission from a radar gun modulated
> in any way so that the gun can distinguish the signal it
> sent out from the signal coming back in IN THE SAME BAND?
> Examples of extraneous noise are: door openers, other police
> radar guns in the vicinity, radar jammers, and probably the
> 3K background.
> -- 
> Jonathan Clark
> [NAC]!mtung!jhc
 While all of the above is true, the resolved signal is down in the FM range
this means that any strong FM signal will couple beyond the detector stage
of the radar gun. Since radar siganl stregth for these toys is in 100 milliwatt
range, return signals are in the 10-1000 microwatt range. This implies that a
strong signal would be less than a watt, if the source is very close. A
handheld FM transmitter or the FM car radio (genrally fould in Police cars)
would produce such a signal of the required stregnth. The toys which
police currently use are too cheap to have the required sheilding and signal
rejection to do away with this problem. Note that an escort or similar detector
needs only to be 1% as effective, to have the same ablity to detect the signals
presence, as the radar gun. Detection of a USEABLE signal requires
more sofisticated circuitry, plus the transmitter stage plus a stage to resolve the speed. When one compares the price of a radar gun to an escort (or
if one considers the cost of the components involved in making an ECM 
device) one is lead to the conclusion that these toys should be banned from use.


			enough of my ranting,
				FTG

ps dietz etz