Does ClearBoost work with an unlocked iPhone?

Antennas are, by their nature, "tuned." Specifically, whatever length the antenna is will determine the RF wavelength that it "hears" best. This is just how antennas work.

ClearBoost's antenna is purposely measured to match the 850MHz wavelength range used by the only U.S.-authorized provider of service for iPhone. (Which seemed like a good idea, in a case for iPhone.)

This size antenna works, necessarily, less well the further you get from that wavelength. But even at the 1900 MHz of *another* well-known service provider (who shall not be named), some benefit will be realized; just not as much as at the 850MHz range.