Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!bionet!agate!shelby!unix!garth!jeff
From: jeff@garth.UUCP (Jeff Kaskey)
Newsgroups: sci.electronics
Subject: Re: Police-radar countermeasures (and rockets)
Summary: how about detecting their radios?
Message-ID: <3211@garth.UUCP>
Date: 17 Aug 89 23:06:53 GMT
References: <414@ctycal.UUCP> <19212@vax5.CIT.CORNELL.EDU>
Reply-To: jeff@garth.UUCP (Jeff Kaskey)
Distribution: na
Organization: INTERGRAPH (APD) -- Palo Alto, CA
Lines: 30

In article <19212@vax5.CIT.CORNELL.EDU> max@ee.cornell.edu  (Max Hauser) writes:

>When you have *any* kind of steady narrowband emitter, even a very small
>one like the local oscillator (LO) in a superhet receiver, a great deal
>of physics and mathematics aids the cause of anyone who wants to detect
>it.  Approached from the proper signal-processing perspective, such
>emitters stick out in the electromagnetic environment like a magnesium
>flare in a darkened room, and can be detected at almost arbitrarily low
>amplitudes with processing-gain techniques.
>


>From past experience as an electronic-countermeasures engineer for the
>US government, I believe that detecting continuous narrowband emitters
>is not even considered an interesting, let alone a challenging, technical
>problem.  


So then, following the thread, it should not be difficult to construct
a circuit which detected the presence of a (just as an example :-))
nearby police radio, as is likely to be truned on in any cop car which
might be pacing, clocking or radaring you.  Interesting.  Anyone got
any idea of the LO used in your average (Motorola ?) police redio?
Radio shack publishes a booklet detailing the transmitting frequencies
of most major cop shops, but do they all use the same LO?  How far is
this from the LO in an FM radio? CB? celular phone?

inquiring minds want to know....

-jeff