OMEGA was the first truly global radio navigation system for aircraft, operated by the United States in cooperation with six partner nations.
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OMEGA was originally developed by the United States Navy for military aviation users. It was approved for development in 1968 with only eight transmitters and the ability to achieve a four mile (6 km) accuracy when fixing a position. Each Omega station transmitted a very low frequency signal which consisted a tone/duration unique to the station that was repeated every ten seconds. By comparing the phases of received signals, and radionavigation principles, an accurate fix of the receiver's position could be calculated. OMEGA employed hyperbolic radionavigation techniques and the chain operated in the VLF portion of the spectrum between 10 to 14 kHz. Near its end, it evolved into a system used primarily by the civil community. By receiving signals from three stations, an Omega receiver could locate a position to within 4 nautical miles (7.4 km) using the principle of phase comparison of signals.[1]
Omega stations used very extensive antennas in order to transmit their extremely low frequencies. They used grounded or insulated guyed masts with umbrella antennas, or wire-spans across fjords. Some Omega antennas were the tallest constructions on the continent where they stood or still stand.
When six of the eight station chain became operational in 1971, day-to-day operations were managed by the United States Coast Guard in partnership with Argentina, Norway, Liberia, and France. The Japanese and Australian stations became operational several years later. Coast Guard personnel operated two US stations: one in LaMoure, North Dakota and the other in Kaneohe, Hawaii on the island of Oahu.
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. Several of the towers were then soon demolished.
Some of the stations, such as the LaMoure station, are now used for submarine communications.
There were nine Omega stations in total:
Bratland Omega Transmitter (station A - ) situated near Aldra was the only European Omega transmitter. It used a very unusual antenna, which consisted of several wires spun over a fjord between two concrete anchor blocks 3500 metres apart, one situated at and . One of these blocks was situated on the mainland of Norway and the other on Aldra island. The antenna was dismantled in 2002.
Trinidad Omega Transmitter (station B until 1976, replaced by station in Paynesville, Liberia) situated in Trinidad (at ) used as antenna a wire span over a valley. Its buildings are still there.
| Paynesville Omega Mast | |
|---|---|
| General information | |
| Status | Demolished |
| Type | Guyed grounded mast equipped with umbrella antenna |
| Location | Paynesville, Liberia |
| Completed | 1976 |
| Destroyed | May 10, 2011 |
| Height | 417 m (1,368.11 ft) |
| Design and construction | |
| Main contractor | US Coast Guard |
Paynesville Omega Transmitter (station B - ) was inaugurated in 1976 and used as radio antenna an umbrella aerial mounted on a 417 metre tall grounded guyed mast of lattice steel, which was the tallest structure ever built in Africa. The station was turned over to the government of Liberia after the termination of the Omega Navigation System on September 30, 1997. Access to the tower was unrestricted and it was possible to climb the abandoned mast until it was demolished years later on May 10, 2011. The area occupied by the transmitter is to be used for the construction of a modern market complex that will provide additional space for local marketers and reduce congestion at Paynesville's Red Light Market, Liberia's largest food market.[1]
Kaneohe Omega Transmitter (station C - ) was one of the two stations operated by the USCG. It was inaugurated in 1943 as VLF-transmitter for submarine communication and used as antenna a wire span over Haiku Valley. At the end of the sixties it was transformed into a transmitter for the OMEGA Navigation System.
| La Moure Omega Mast | |
|---|---|
| General information | |
| Status | Complete |
| Type | Mast radiator insulated against ground |
| Location | La Moure, North Dakota, USA |
| Height | 365.25 m (1,198.33 ft) |
| Design and construction | |
| Main contractor | US Coast Guard |
La Moure Omega Transmitter (station D) situated near La Moure, North Dakota, USA at ) was the other station operated by the USCG. It used a 365.25 metre tall guyed mast as an antenna, which is insulated against ground. Since the shutdown of the Omega Navigation System, it is used for VLF transmissions to submarines.
| Chabrier Omega Mast | |
|---|---|
| General information | |
| Status | Destroyed |
| Type | Guyed grounded mast equipped with umbrella antenna |
| Location | Chabrier, Réunion |
| Completed | 1976 |
| Destroyed | April 14th, 1999 |
| Height | 428 m (1,404.20 ft) |
| Design and construction | |
| Main contractor | US Coast Guard |
Chabrier Omega Transmitter (station E ) near Chabrier on Réunion at ) used an umbrella antenna, which was installed on a 428-metre tall grounded guyed mast. The mast was demolished on April 14, 1999 by explosives.
Station F, Trelew, Argentina,
Station G, near Woodside, Victoria, Australia,
| Omega Mast, Tsushima | |
|---|---|
| General information | |
| Status | Destroyed |
| Type | Mast radiator insulated against ground |
| Location | Tsushima, Japan |
| Completed | 1973 |
| Destroyed | 1998 |
| Height | 455 m (1,492.78 ft) |
| Design and construction | |
| Main contractor | US Coast Guard |
Shushi-Wan Omega Transmitter (station H) situated near Shushi-Wan on Tsushima Island at ) used as its antenna, a 389-metre tall tubular steel mast, insulated against ground. This mast, which was built in 1973 and which was the tallest structure in Japan (and perhaps the tallest tubular steel mast ever built) was dismantled in 1998 by crane. On its former site, an approximately 8 metre-tall memorial consisting of the mast base (without the insulator) and a segment was built. On the site of the former helix building there is now a playground.
In addition to the nine operational Omega towers, the tower at Forestport, NY was used for early testing of the system.