I have a Garmin Streetpilot 2720 and haven't been having any problems getting a fix but I see many people opt for an external antenna. My GPS is mounted on a Ram with a clear view to the sky, the only thing that comes close to it would be me or a windshield, both at least 2 ft away. I have sucessfully used the GPS under the dash of my car by the speedometer and never had a problem losing signal. However, I haven't really taken my GPS into the city (Iowa isn't know for its architecture) and I've got several trips coming up. Is it worth it to go to all the trouble of buying one and having even more wires to plug in?