11 January 1998
Thanks to MH and SS
Date: Sat, 10 Jan 1998 18:49:30 -0800 To: cypherpunks@cyberpass.net From: Steve Schear <schear@lvdi.net> Subject: GPS Jamming [FWD] I think this might have been mentioned in a CP thread sometime back. At least it should have ;-) --------------- Date: Fri, 9 Jan 1998 22:29:14 +0000 From: "Marcus L. Rowland" <mrowland@ffutures.demon.co.uk> Subject: GPS Jamming *New Scientist* (8 Jan 1998, http://www.newscientist.com) included an article saying that a Russian company called Aviaconversia was offering a 4-watt GPS/Glonass jammer for less than $4000 at the September Moscow Air Show. It says that it could stop civilian aircraft locking onto GPS signals over a 200 Km radius; military aircraft would be harder to jam, but a more powerful unit could be built. The risks (terrorism etc.) are fairly obvious, and it's mentioned that it would probably be easy to build one even if this company's product is somehow removed from the market. Marcus L. Rowland http://www.ffutures.demon.co.uk/ ------------- GPS uses a wideband Direct Sequence Spread Rectum technology. DSSS, as implemented in GSP, is excellent for distance an direction finding due to its inherent, very accurate, time base. In order to conserve satellite power and provide a reasonable signal level at small (e.g., handheld) receivers, it spreads a low data rate signal over wide band, achieving a 63dB 'process gain' (equivalent to about a 2 million fold increase in receive signal level). DSSS signals (in general) can be jammed by very narrow (e.g., CW or continuous wave) carriers, especially pulsed, with relatively modest power. GPS includes significant provisions for anti-jam and although I haven't done a detailed analysis, I'd be surprised if a 4-watt transmitter would render a 200 km radius unfit for GPS navigation. See "Spread Spectrum Communications Handbook," ISBN 0-07-057629-7. --Steve PGP mail preferred, see http://www.pgp.com and http://web.mit.edu/network/pgp.html RSA fingerprint: FE90 1A95 9DEA 8D61 812E CCA9 A44A FBA9 RSA key: http://keys.pgp.com:11371/pks/lookup?op=index&search=0x55C78B0D --------------------------------------------------------------------- Steve Schear | tel: (702) 658-2654 CEO | fax: (702) 658-2673 Lammar Laboratories | 7075 West Gowan Road | Suite 2148 | Las Vegas, NV 89129 | Internet: schear@lvdi.net ---------------------------------------------------------------------