I was going to do this as a project on my Connect nav but never got round to it. I think it is the same plug as the GPS antenna, which is known as a GT5 connector. I was going to get a normal internal antenna from eBay with an "F-connector" on the end, chop it off and use one of the GT5 connectors from a GPS mouse (£10 on eBay) Im not sure how well it will work though, it might not get the signal gain levels you need to hold a conversation. Im interested to know the results though!!