Abstract: A monopulse radio direction finding and tracking system having the capacity of detecting the presence of multiple radiating sources within the effective beamwidth of the monopulse antenna and causing the monopulse antenna to move toward and align its boresight with one of the multiple sources. Signal processing is provided that implements an algorithm based on the amplitudes and absolute magnitudes of signals from a receiver sum channel, elevation and azimuth difference channels, and elevation and azimuth angular error channels. The algorithm utilizes the differences in the ratio of signals present in these channels when a single radiating source is present and when multiple sources are present. Steering control circuits are provided that bias the azimuth and elevation antenna steering servo system to cause the antenna to align its boresight with one of such multiple sources.