A commutated antenna direction finder is a device used to locate the direction of a radio signal. There are several synonyms for this device, including a radio direction finder, a radio compass, a radio bearing indicator, and an RDF. These synonyms are used interchangeably and refer to the same device. The commutated antenna direction finder works by using a rotating antenna to determine the location of a radio signal. It is commonly used in aviation and maritime navigation, but can also be used in amateur radio or other applications where the location of a signal needs to be determined.