In 1999, a Russian firm, AviaConversia offered for sale four different models of GPS jammers (for about $4000 each). This gear only puts out 4-8 watts, making them very tough to find and bomb. And the jammers can effectively block GPS signals out to 150-200 kilometers, depending on terrain. The jammer can run off batteries and weighs between 18 and 26 pounds (without batteries). When operating, the jammers consume less than 25 watts of power. Since AviaConversia announced their product, plans for building your own (from off the shelf components) have appeared on the Internet. Apparently, the parts can be obtained for less than a hundred dollars. Soldering skills required. Already assembled units are also available on the Internet for as low as $40. AviaConversia has since apparently disappeared. AviaConversia made much of its connections with the Russian armed forces and the implied assurance that its jammer worked. There have been no reports of the cheap jammers on the Internet being used, or to what effect. U.S. military experiments found that the cheap jammers were not that effective, and larger ones, built from off the shelf components, and costing nearly $10,000. For the last few years, the Department of Defense has been building and testing GPS Jammer detectors, and building homing systems sensitive to go after them. Other nations, such as Australia, have also been working on ways to defeat jammers. One method already available is to change the GPS frequency. But someone with access to the GPS satellites has to do this.
