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

The method used to locate sources of noise interference or jamming is radio direction finding. This technique involves determining the direction from which a radio signal is coming. By utilizing antennas and receiver technology, an operator can identify the bearing of the interference source. This is particularly useful in ham radio operations, as it allows operators to pinpoint the origin of unwanted signals that may disrupt communication.

Radio direction finding can involve various techniques, such as rotating a directional antenna to determine the strongest signal direction or using multiple fixed antennas to triangulate the position of the interference. This is essential for addressing issues related to jamming and ensuring clear communication channels.

Other options like echolocation and Doppler radar are not applicable in the context of locating radio frequency interference. Echolocation is primarily a technique used in sonar applications, while Doppler radar focuses on measuring the velocity of objects rather than locating signals in the radio spectrum. Phase locking, on the other hand, pertains to synchronizing signals rather than detecting their source. This makes radio direction finding the only relevant method among the choices provided for identifying sources of noise interference or jamming.