A technique for reducing multipath distortion in an FM receiver, with a plurality of switchable antennas, provides a fast distortion detector that monitors a received signal for significant distortion events of less than about 15 microseconds in duration. In response to a multipath event, the output of the fast distortion detector initiates a search for a lower distortion (better quality) antenna. To prevent frequent antenna searches from causing an audible disturbance, a threshold is introduced to desensitize the fast distortion detector. Threshold decay is a function of an overall received RF signal level. A slow distortion detector is also provided that measures distortions of the received signal relating to signal quality.