Why cell phones find roadblocks.

• Position: Your Life - Brief Article

It's 6 p.m. Friday, and you're trying to make a call on your cell phone, but you can't get a dial tone or a voice indicates that there are no cells available. The problem, explains electrical engineering professor Dennis Silage, Temple University, Philadelphia, Pa., is everyone else is trying to use his or her cell phone and there just aren't enough frequencies to handle it. "Unlike a lot of other countries that have radio frequency spectrum to play with, the U.S. doesn't because the government and the military traditionally have held on to large blocks of the frequencies. Plus, we have a very extensive television broadcast and data...