Employ a GPS jammer. Most U.S. jets, bombs and ships use the satellites for navigation and timing. The squadron built one jammer small enough to fit in a cigarette pack. It had a weak signal and would have to be close to the antennae to work. Another jammer, about 15 feet tall, could interrupt the signal from farther away. It was relatively easy to build. The airmen bought the plans online for $35. The amplifier came from an electronics store, the generator from a ham-radio operators convention. The rest - PVC pipe, copper tubing, wood supports and hardware - came from a home improvement store. The total cost was less than $9,000. "This is not something cosmic," said Lt. Col. Rad Widman, who until recently commanded the squadron. GPS jamming usually can be defeated by changing a channel frequency, but operators must realize they are being jammed, Widman said. Next week-What traffic analysis tells,Wardriving warbases.us.http://www.gazette.com/stories/0811top2.php