an fm stereo receiving system and a method for aligning phases of rf signals received by multiple antennas . the fm stereo receiving system includes two antennas for receiving rf signals having a common frequency but potentially different phases . the system also includes an fm receiver having a detector output and a pilot output on which a pilot tone , such as a 19 khz pilot tone , is present . a summer is included in the system for summing the rf signals and providing the summed signal to the receiver . the amplitude modulator of the system resides between one of the antennas and the summer to amplitude modulate the antenna &# 39 ; s rf signal at a perturbation frequency which is a whole number multiple greater than 1 of the pilot tone . the receiver thus produces on its phase detector output a phase signal having a frequency equal to the perturbation frequency and a magnitude corresponding to the phase error between the rf signals which is connected in a feedback loop to align the phases .