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LF & MF Nondirectional Radio Beacons

March 1st Fact-of-the-Day

The first nondirectional radio beacon (NDB) was placed in service in 1921. It was operated by the Bureau of Lighthouses to assist marine navigation by means of manual radio direction finders. A manual radio direction finder that was light enough for airborne use was developed in 1934. Much easier-to-use automatic direction finders (ADFs) where developed soon after that and thousands were installed in aircraft. A large number of LF and MF NDB's were installed throughout the world between 1934 and 1955. By June 30, 1955, 173 were operating in the United States. Since then a variety of much more dependable and accurate systems have been developed and most of the former NDB's have been decommissioned. The few that still remain in service are kept operating primarily to provide means of emergency navigation using simple equipment if more sophisticated modern systems fail. ©2005 Martek, International. All rights reserved.

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