Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ames!vsi1!daver!lynx!neal
From: neal@lynx.uucp (Neal Woodall)
Newsgroups: sci.electronics
Subject: Re: Car electronics projects
Summary: Non-linear junction detectors are easily fooled by any semiconductors
Message-ID: <5926@lynx.UUCP>
Date: 29 Jul 89 00:09:41 GMT
References: <768@xroads.UUCP> <7200037@silver>
Reply-To: neal@lynx.UUCP (Neal Woodall)
Distribution: usa
Organization: Lynx Real-Time Systems Inc, Campbell CA
Lines: 23

In article <7200037@silver> commgrp@silver.bacs.indiana.edu writes:

>Another method would be the 
>principle used to locate passive bugging devices:  The target area is 
>bombarded by microwaves and a receiver looks for harmonics generated 
>of the exciting signal, generated by semiconductor junctions.  In the 
>latter two cases, range would probably be only a few feet.

Good point. These kinds of devices (ie, look for semiconductors by looking
for harmonics of a driving signal produced by the non-linear junctions)
would probably react to ANY semiconductors, and cars are FULL of semi-
conductors these days. Remember how the Soviets "sabotaged" the US embassy
they were building in Moscow: they filled the poured concrete structure
with diodes and transistors! The idea was to put so many semiconductor
junctions in the structure of the building as to render the detection
of any specific junctions (the bugging devices) impossible.

The device that looks for the radar detector's local oscillator signal is
probably the more practical of the two.



Neal