Xref: utzoo sci.electronics:13267 rec.autos:36157 Path: utzoo!attcan!uunet!decwrl!sdd.hp.com!zaphod.mps.ohio-state.edu!samsung!cs.utexas.edu!mailrus!iuvax!daemon From: commgrp@silver.ucs.indiana.edu (BACS Data Communications Group) Newsgroups: sci.electronics,rec.autos Subject: Re: Detecting Radar Detectors Message-ID: <52901@iuvax.cs.indiana.edu> Date: 1 Aug 90 16:37:17 GMT Sender: daemon@iuvax.cs.indiana.edu Lines: 62 to sci.electroics and rec.autos: jkimble@bally.Bally.COM (The Programmer Guy) writes: Subject: Detecting Radar Detectors >I saw a story on the world news a few weeks ago regarding drivers >(primarily 18-wheelers) using radar detectors. During the news >segment, the reporter was talking to a highway patrol officer who was >using a device to detect if the oncomming vehicle was using a radar >detector. >...How do these detectors of radar detectors work? ... A friend sent me an article from a Virginia newspaper, _Lessburg Today_, July 13, 1990, entitled "Radar 'Detector Detictor' Cruises Local Primary Roads." "...The $1100 device detects microwaves "leaking" from operating radar detectors... Originally developed in Canada, where radar detectors are illegal... The VX6-2 detector is being fornished at no cost on a loan basis to the state police by the Insurance Institute for Highway Safety, a private research organization funded by insurance companies..." There's a picture of the beast, which is housed in a box aprox. 3 x 4 x 6", with two knobs and a LED on the front. It looks home-brewed. --- This article seems to confirm rumors that the insurance cartel wants to outlaw radar detectors everywhere in the U.S., either through the legislators they own, or by excommunicating/sh*tlisting policyholders who use them. These devices have been used in Canada for several years. They are for real, and apparently very effective. Superhet radar detectors work like little spectrum-analyzers: The local oscillator (11.5 GHz +/-) is a Gunn diode with a varactor to sweep its frequency. The first i.f. is 1 GHz, followed by further conversion and circuits which detect valid alarm conditions. K-band is detected via a harmonic of the local oscillator; I haven't done the arithmetic. The advantage of this method is that it searches a wide band but retains high sensitivity. The local oscillator, varactor and mixer diodes are all inside a cavity at the end of the horn antenna. A series of screws projecting into the horn form a trap to suppress local oscillator radiation, but are only partially effective. Some brands of radar detector mutually interfere because of local-oscillator radiation. In WW II, the Germans installed radar detectors on U-boats. These also had a problem with local-oscillator radiation, and Allied ASW aircraft were able to home-in on them without radar. A detector-detector could probably be made by modifying a conventional radar detector: Mechanically retune its local oscillator to 1 GHz above or below 11.5 GHz, and remove the trap screws. -- Frank Reid W9MKV reid@ucs.indiana.edu 26 states on 10 GHz. ZAP! ;-)