From: Johnathan Sawyer (jfsawyer@???.???)
Subject: Re: GPS Jamming? 
Newsgroups: sci.geo.satellite-nav
Date: 1995-02-08 22:56:57 PST 

Rob Robinson,773-4691,EW 115 (rrobin@?????.??.???) wrote:

: Has anybody else reading this noticed a similar "jamming" effect, regardless 
: of the source?  I have not yet encountered any difficulties with my Garmin 
: GPS 40, although I haven't been close to any RF sources other than an FM 
: transmitter at around 100 MHz (the receiver was within 100 feet of the 
: transmitter antenna).  I don't know what the transmitter power was.  It was 
: a commercial FM station (I don't remember the callsign).


It turns out the 2nd Harmonic of the aural carrier of a US NTSC Chan 66
television transmitter falls right in the middle of the 1575.42 MHz GPS
Band.  I have been victimized by a low power (1KW) television translator
in Boulder Co operating on CH 66.  Although the harmonic level was -80 dB
(within FCC limits), it still managed to wipe out our GPS from several
miles away.

In complaining to the owner of the station I was embarassed to discover
the translator was the brand designed by me many years before (:(.

Jonathan Sawyer