[ronobvious] purchased a Ralink based USB WiFi adapter for use with Aircrack-ng. It worked well so he decided to add an external antenna connector. The connector from Linx Technologies that he chose is really what makes this installation clean. It’s a card-edge design so you just slip it over the end and solder the pin and ground leg. He’s got a link to Tobias Hain’s similar mod and Tobias has a link to a another antenna project as well.
