A manual radio direction finder is a device that helps sailors and airmen navigate by locating the direction of incoming radio signals. There are several synonyms for this device, including radio compass, DF equipment, direction finding equipment, and RDF. These terms all refer to the same type of technology but may differ in their functionality or specific use. The radio compass is a term commonly used in aviation and is often integrated into aircraft navigation systems. DF equipment and direction finding equipment are more general terms that can refer to any device used to determine direction based on radio signals. RDF, on the other hand, is a more technical and precise term that describes the specific process of radio direction finding.