Before revision: 300px|Radiotriangulation scheme using two direction-finding antennas (A and B) Direction finding antenna near the city of Lucerne, Switzerland Direction finding (DF), or radio direction finding (RDF), is the use of radio waves to determine the direction to a radio wave source.
After revision: 300px|Radiotriangulation scheme using two direction-finding antennas (A and B) Direction finding antenna near the city of Lucerne, Switzerland Direction finding (DF), or radio direction finding (RDF), is the use of radio s to determine the direction to a radio wave source.