The SCR-277 was a mobile, trailer mounted radio range set for radio guidance of aircraft. It was standardized by the U.S. Army in June 1941.
K-29 trailer for SCR-277, 1944
Radio navigation or radionavigation is the application of radio waves to determine a position of an object on the Earth, either the vessel or an obstruction. Like radiolocation, it is a type of radiod
Amelia Earhart's Lockheed Electra had a prominent RDF loop on the cockpit roof.