An aerial drone or unmanned aerial vehicle (UAV) is provided for radar calibration testing. The drone includes an airframe including a fuselage with nose and tail, wings and elevators. The drone includes at least one antenna attached to the airframe, as well as a signal adapter coupled to the antenna to receive impinging radar signals and transmit an electromagnetic (EM) field that effectively cancels or combines with the scattered field of the drone, depending upon the adapter's mode of operation. In the first mode of operation, the adapter transmits an EM field that has an opposite phase to the drone's scattered field thereby reducing the radar cross-section of the drone. In the second mode, the adapter transmits an EM field that is in-phase with the scattered field thereby increasing the radar cross-section of the drone.