it came on the car. i tried a quick google search but didn't come up with anything. i had this same head unit in two other gtps and had the signal problem. my buddy has a monte and he had that little antenna on his window, too. i don't know if its a signal booster or another antenna. it is mounted on the back window and the wire goes through the glass. i don't know where it runs from there but it doesn't go into the dash where the stereo is. anyway, i get am radio and all the stations and hd stations come in clearly with that little doodad.
go to a car audio shop or to best buy or something and ask.
