That one is not a universal thing. It generally only works if your phone is designed to work with an external antenna to begin with and the routing for the external antenna is through the same connector that you use for power. Depending on the type of power cord used (straight or coiled, paired or coax...), the cords impedance level, how it is terminated and where it plugs into the phone relative to the actual antenna you may or more likely may not see any change in performance. In an emergency it might be worth a shot but it is not something I would depend on.

-Eric