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Alpha (also called RSDN-20 ) is a Russian system for long range radio navigation. RSDN in Russian stands for Радиотехническая Система Дальней Навигации (radiotehnicheskaya Sistema Dal'ney Navigatsii), which translates to English as "radio-technical long-distance navigation system".
ALPHA was used to determine positions of aircraft, ship and submarines (in underwater position). This system was being developed in parallel with U.S. OMEGA System and also works in VLF-range. ALPHA coverage is up to 10,000 km from the master station, position error of 2.5…7 km.
The alpha system consists of three transmitters, which stand in the proximity of Novosibirsk, Krasnodar and Khabarovsk. Two other transmitters at Revda and Seyda are not currently operational (2010). These transmitters radiate signals of 0.4 second duration in a 3.6 second cycle on the frequencies F1: 11.904761 kHz, F2: 12.648809 kHz and F3: 14.880952 kHz. From the phase difference of the received signals a location can be determined. Other alternative frequencies: F3p: 14.881091 kHz, F4: 12.090773 kHz, F5: 12.044270 kHz, F6: 12.500000 kHz, F7: 13.281250 kHz, F8: 15.625000 kHz, Fx: 12.700000 kHz.
Much like the masts used for the US OMEGA, for technical reasons the masts of Alpha must be very tall. Unfortunately no data are available for their height.
Since January 2014 are disabling some transmitters.
- Alpha transmitter Novosibirsk: ( )
- Alpha transmitter Krasnodar: ( )
- Alpha transmitter Khabarovsk: ( )
- Alpha transmitter Revda: ( )
- Alpha transmitter Seyda: ( )
- OMEGA, the Western counterpart of the Alpha Navigation System, no longer in use.
- LORAN, low frequency terrestrial radio navigation system.
- CHAYKA, the Russian counterpart of LORAN