can i get a external antenna or better internal one for my true mobile 1300

is there a way i can hook up a external antenna to my truebobile 1300 wlan internal wireless card? or a antenna amplifier or somthin? my friend next door lets me use his wireless broadband connection but i have to sit outside or if im inside it connects but not very good, i have to hold it by a window. i just need a little bit stonger antenna.