Terror threat

Cellphone Bombs: The New American Terror

...To be sure, cellphone jamming in a small or fixed area can be useful. Many prisons jam incoming signals. The U.S. Secret Service reportedly possesses jammers that accompany presidential motorcades.

The U.S. military equips many of its armored vehicles with radio jammers, creating an electronic bubble in which many remotely triggered bombs won’t detonate. More powerful airborne military jammers can sweep away signals underneath the emitting aircraft.

But jamming cellular signals across a wider area can be highly problematic. For starters, the most modern cellular services take advantage of what’s called “frequency-hopping.” That is, they can rapidly move signals across different frequencies more or less to avoid overcrowding. This complicates jamming. The more a signal hops, the more frequencies you’d have to jam.