Which of the following methods is used to locate sources of noise interference or jamming?

Radio direction finding (RDF) is the practice of using specialized receivers and antennas to determine the bearing of a transmitted radio signal. By taking signal bearings from multiple geographic locations, operators can triangulate the exact physical source of noise, interference, or a jammer. The distractors represent entirely different technologies. Doppler radar and echolocation are used to bounce signals off physical objects to determine their location or speed, while phase locking is a circuit technique used in oscillators. Only RDF is used to track down the source of an active radio emission.