Radio direction finders (RDF) use directional antennas to compare signal strengths from radio sources and determine the direction of the source. They have been used since the early 1900s for navigation by ships, small boats, and aircraft. RDFs work by tuning a receiver to a frequency and rotating a loop antenna to find the strongest signal, indicating the direction of the radio station. Operators would take bearings from multiple stations to locate their position by plotting the intersecting bearings on a map. RDFs were commonly used for maritime navigation and aircraft before modern electronic navigation systems.

1. ELECTRONIC NAVIGATION 1 2/M Crispin Echavez instructor

2. Navigational Equipments(RDF) Radio Direction Finder

3. RADIO DIRECTION FINDER

4. Radio direction finder (RDF) device for finding the direction to a radio source. Radio's ability to travel very long distances and "over the horizon“. Good navigation system for ships, small boats, and aircraft that might be some distance from their destination.

5. HISTORY John Stone Stonein 1902 (U.S. Patent 716,134) Lee de Forest in 1904 (U.S. Patent 771,819) EttoreBellini and Alessandro Tosi in 1909 (U.S. Patent 943,960) Frank Adcock in 1919 (UK Patent 130,490) The US Army Air Corps in 1931

6. OPERATION works by comparing the signal strength of a directional antenna pointing in different directions. used by land and marine-based radio operators. adopted for both ships and aircraft,

7. OPERATION con’t used in the 1930s and 1940s. circular loops mounted above or below the fuselage. enclosed in an aerodynamic, teardrop-shaped fairing. employed large metal loop antennae, similar to aircraft

8. OPERATION con’t RDF operator would first tune the receiver to the correct frequency. turn the loop. long wave (LW) medium wave (AM) By taking bearings to two or more broadcast stations and plotting the intersecting bearings, the navigator could locate the relative position of his ship or aircraft.

9. USAGE IN MARITIME NAVIGATION Position fixing

10. Also called Radio Compass. radio receiver and directional antenna system used to determine the direction of the source of a signal. It most often refers to a device used to check the position of a ship or aircraft, although it may also direct a craft’s course or be used for military or investigative purposes.

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