The invention relates to an in-vehicle antenna system and method. Concretely, an antenna system connectable to a vehicle includes an exterior antenna, an interior antenna, and a data transmission line. The vehicle has a wall including an outer surface and an inner surface that generally opposes the outer surface, where the inner surface and the outer surface cooperate together to create an aperture. The wall defines an exterior environment and an interior cabin. The exterior antenna is located within the exterior environment and is connectable to the vehicle. The interior antenna is located within the interior cabin defined. The data transmission line transmits RF signals and is in communication with both the exterior antenna and the interior antenna. The transmission line passes through the aperture located in the plate between the exterior antenna and the interior antenna.