Systems and methods for providing antenna calibration can be used in a variety of applications. A method of calibrating an antenna array for use in a traffic advisory system or traffic alert and collision avoidance system provide a mechanism that renders complex combining circuitry unnecessary in the array. A method can include receiving an unsolicited reply that contains absolute position information of an intruder aircraft. The method can also include determining a bearing of a signal encoding the reply based on a phase relationship of the signals from an antenna array not configured to operate with an internal self-test phase calibration mechanism. The method can further include comparing the bearing based on the phase relationship with a bearing calculated by a comparison of the absolute positions of a host aircraft and the intruder aircraft. The method can additionally include calibrating the antenna array based on the result of the comparison.