A mobile device can detect, select and use an external antenna supported by an attached accessory device. The mobile device queries the accessory device whether it supports an external antenna and receives an indication of whether the accessory device supports external antennas. The indication can comprise a list of accessory device pins operatively coupled to supported external antennas. The mobile device selects an external antenna for use by the mobile device. The selection can comprise selecting a mobile device pin operatively coupled to the selected external antenna. The selected mobile device pin can be a predetermined pin or a pin that is both operatively coupled to a supported external antenna and configured to operate as an external antenna pin. The mobile device can use the selected external antenna. The mobile device can switch between an internal antenna and an external antenna operatively coupled to a selected mobile device pin.