Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!gem.mps.ohio-state.edu!ginosko!usc!ucsd!brian
From: brian@ucsd.EDU (Brian Kantor)
Newsgroups: sci.electronics
Subject: Re: Police-radar countermeasures (and rockets)
Message-ID: <1907@ucsd.EDU>
Date: 18 Aug 89 15:34:44 GMT
References: <414@ctycal.UUCP> <19212@vax5.CIT.CORNELL.EDU> <3211@garth.UUCP>
Reply-To: brian@ucsd.edu (Brian Kantor)
Distribution: na
Organization: The Avant-Garde of the Now, Ltd.
Lines: 36

Receive-only anti-police ECM:

The IF depends on the band and brand, but the majority of cop radios
in SoCal are Motorola Micors and Syntors; they use an 11.7 MHz IF
and you'll find the LO injecting into the mixer at +/- 11.7 from
the receive frequency.  Thus you can tune a sensitive receiver to
the appropriate frequency and when the squelch starts to burble,
there's a cop-car ["fuzz-mobile"] in the vicinity.  The radio in
the local police helicopter ["whirly-pig"] seems to radiate more,
but they tend to hang out on the "tactical" or "air-support" channels
so you might not be listening there.

Another popular IF is 10.7 MHz; same technique applies.  Older
radios such as the Motrac used 12MHz.  Ask a local technically-inclined
ham; he'll probably know what's popular in your area.

The CHP has a problem with walkies - they run low-band radios
(around 41 MHz) to get really good coverage in mountain passes,
valleys, and canyons.  But nobody makes a really good low-band
walkie, and the antenna is too big anyway - and they don't run
enough power.  So lots of CHP cars are equipped with cross-band
.5w walkie repeaters that allow the officer to carry a high-band
(150MHz) walkie with him and use the car's 100w+ low-band radio.
So you just program the walkie talkback channel into your scanner
and if you hear the dispatcher, you're probably within a 1/2 mile
of a CHiPpie.  Since they don't use radar, that's likely the only
way you'll have some warning - those black mustangs with no external
lights really aren't very obvious.

And of course an X/K band ECM receiver (aka "radar detector") is
essential in towns that enhance their revenues with speeding tickets.

Snoop and listen - while you still can.

"Those who forsake liberty for security deserve neither."
					-- Franklin