Omega Navigation System
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Omega was the first truly global radionavigation system for aircraft operated by the United States of America.
Omega was initially planned in 1968, and was operational in 1971.
There were eight Omega stations Bratland, Norway (A), Paynesville, Liberia (B), Kaneohe, Hawaii (C), LaMoure, North Dakota (D), Chabrier, Réunion (E), Trelew, Argentina (F),Woodside, Australia (G) and Shushi-Wan, Japan (H). The station in Australia was originally intended for New Zealand but was moved to Australia after protests from anti-war protestors.
Each Omega station transmitted a very low frequency signal which consisted of a pattern of four tones unique to the station that was repeated every ten seconds. Because of this and radionavigation principles, an accurate fix of the receiver's position could be calculated.
Due to the success of the Global Positioning System the use of Omega declined during the 1990s, to a point where the cost of operating Omega could no longer be justified. Omega was permanently terminated on September 30, 1997 and all stations ceased operation.
The LaMoure station is now used by the United States Navy as an extremely low frequency station for submarine communications.
Antennas
Omega stations used very extensive antennas in order to transmit their extremely low frequencies. Specifically, they used grounded or insulated guyed masts with umbralla antennas, or wire-spans across fjords. Some Omega antennas were the tallest constructions on the continent where they stood or still stand.