Adaptive radio direction finding system

A radio direction finding system for determining the direction of radio frequency signal transmissions with respect to a receiving location, comprising:

• an antenna which performs 360.degree. sweeps for receiving radio frequency signals from sources of radio frequency signal transmissions;
• receiver means coupled to said antenna and responsive to said received radio frequency signals for producing a plurality of output signals, each one of said plurality of output signals corresponding to said received radio frequency signals, said output signals containing information indicative of the signal strength and bearing of said received radio frequency signals;
• means responsive to said output signals for extracting said signal strength and bearing information and for providing corresponding signal strength signals and bearing signals indicative thereof;
• characterized by:
• means responsive to said signal strength signals and said bearing signals for determining if the magnitude of said signal strength signals are greater than a threshold magnitude, and for determining that a source of radio frequency signal transmissions is present at a bearing if signal strength signals of a magnitude greater than said threshold magnitude are present at a corresponding bearing for a statistically significant number of antenna sweeps.