I'm a mile from the giant antenna in San Francisco, Sutro Towers. But my phones never really get good reception here. This repeater is good for creating a better signal in your most house or apartment's most vacant cellular airspaces. It's a dual band, in the PCS 1900 MHz and Cellular 800 MHz bands, which covers signals of EVDO, HSDPA, AT&T, T-Mobile, Sprint and Verizon flavors in the US. It grabs a decent signal inside or outside a window, or even better, on a roof, using a big antenna. The repeater connects to the antenna by a long piece of coax, and boosts a signal by up to 55DB. Doing a shitty install, I measured a real world gain of 10-15dB, using the iPhone's field test mode. That's good enough to clear up calls and reduce dropped connections in the ultra dead cellular zone I call my office. Not bad for $350, and now I don't have to leave my desk to take calls.