Talking [Q] Ext Ant

Has anyone messed with the external antenna port on the back of our phones yet? I wanna try to boost my signal with an external antenna (T-Mobile isn't the best), but I'm scared of frying the internal board if I do.

Does anyone know if that is a data port or an actual antenna hook up? Is it safe to run an external?

P.S. For those who don't know, the port is to the right of the sim/microsd card, directly above the battery (maybe 2mm), under the black circle sticker thing. Diagonal from the screw.