I had read somewhere that metallic body of cars reduce the signal charge inside the car, whereas the external antenna gets the charge back to the designated area. This does not need a physical connection for cell phones. One can only visualize the effect in real poor signal areas. Good luck. This is different from the radio signals where you need a physical connections as the strength of radio signals is comparatively low.
Last edited by alokbhargava; 11-26-2011 at 12:02 PM.