June 16, 2009:
The U.S. Department of Defense has ordered another 2,500 JCREW (Joint Counter Radio-Controlled Improvised Explosive Device Electronic Warfare) 3.1 dismounted (wearable) jammers. They cost about $99,000 each. The wearable JCREW jammers will be more useful in Afghanistan, where more of the patrolling is on foot.
Three years ago, the U.S. began using wearable JCREW jammers. JCREW is a further development of the first jammer, the Warlock, which appeared in 2003, mounted in vehicles. The jammers have gone through many revisions, to add more frequencies and better software.
Rolling along in a convoy, with one or more jammers broadcasting, the troops have an electronic "bubble" that made them safe from any wireless IED they had not spotted. It's not uncommon for vehicles to have had an IED go off behind them, the result of the IED detonation crew continuing to send the signal, believing that there might be something wrong with their equipment. In those cases, the patrol often turns around and goes looking for the enemy team, while supply convoys just continue on their way..
In addition to jammers like JCREW and Warlock, several of the U.S. Air Force and Navy electronic warfare aircraft are able to perform the same functions, but over a wider area. This was often used when American troops were in action against the enemy, shutting down IED detonation over the entire combat area, as U.S. troops moved around seeking out and fighting the enemy.
One problem with the jamming was that it kills cell phone operation, as well as use of many other remote electronic devices Iraqi civilians in the area might be trying to use. The locals complain to each other, but asking the U.S. troops to shut it off would be futile, so they don't.
The JCREW jammer has lots of new features, most of which are secret. Terrorist groups have tried to find ways around the jammer, but have been unsuccessful. Most roadside bombs are now set off via a wire connection between the detonator and a nearby guy pressing a button. This has caused more terrorist casualties, and generally made it more difficult for the bombers. The big improvement in JCREW is that it is easier to add new frequencies, and the jammer interferes less with other military communications and sensors. JCREW is also lighter.
A hundred or so lightweight JCREW jammers were sent to Iraq three years ago, for testing. These proved very popular with troops who did a lot of their patrolling on foot. It's become increasingly common for troops to make long movements on foot, to conduct raids or just patrol. The enemy has lookouts who are on the alert for U.S. vehicles, not dismounted American infantry sneaking up on them.