Products for war: Iraqi signal-jamming devices are easy targets

The jamming devices Iraqis have used to try to thwart the U.S. military's vital satellite positioning system have so far proven easy prey: When they're switched on, they become beacons for bombers.

On Tuesday, the U.S. Air Force said it destroyed a half dozen Iraqi jammers that were apparently attempting to send U.S. bombs and missiles off course.

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"In order for them to jam they have to light up," said Pentagon spokeswoman Lt. Col. Christy Nolta. "If they light up we can find them. So it may work once."

White House spokesman Ari Fleischer said Monday that Russian companies had provided global positioning system, or GPS, jamming equipment to the Iraqis. Russia denies supplying the equipment.

The gear is designed to thwart signals beamed to earth from a constellation of more than two dozen U.S. satellites that are the lead navigation tool for everything in the Armed Forces from individual soldiers to tanks and bombs.

The jammers overwhelm GPS signals, which are relatively weak. The Pentagon has long acknowledged that its navigation and guidance systems can be flummoxed by interference, and has sought to install weapons and vehicles with backup guidance systems — or ensure troops could use old-fashioned maps and compasses in the case that GPS is blocked.

So far, the Iraqi GPS jamming threat has turned out to be petty.

Iraqis operating GPS jammers didn't seem to realize they were broadcasting their own locations, said David Isby, a private defense consultant.

"You want to turn it on when a bombing run is under way, then turn it off, move it and run like hell," Isby said.

Since the interference is easily detectable by U.S. electronic warfare receivers, Iraq could only risk short bursts of jamming when bombs are falling or missiles homing on a target, Isby said.

Jammers are inexpensive and relatively low-tech but appear to be manufactured and sold clandestinely by companies in eastern Europe and the former Soviet Union, said Martin Streetly, an expert in radar and electronic warfare technology with the London-based Jane's Information Group.

He said China also appears to be manufacturing jamming equipment aimed at protecting ground sites from precision-guided weapons.