Received Alfa navigation signals at 11.905 kHz, 12.649 kHz, 14.881 kHz. Click on the picture to enlarge.

ON8IM VLF thumb

Wat are Alfa Navigation signals ?

The ALPHA / RSDN-20 radionavigation system is transmitting a 3.6 sec long repeating sequence consisting of six 400 ms long frequency combinations with a 200 ms spacing.

Alpha was used to determine positions of aircraft, ships, and submarines (in underwater positions). The system was developed in parallel with U.S. Omega navigational system, and also works in VLF-range. Alpha coverage is up to 10,000 km from the master station, with a position error of 2.5…7 km.

The Alpha system consists of three transmitters, placed in the proximity of Novosibirsk, Krasnodar and Khabarovsk. Two other transmitters at Revda and Seyda are not currently operational as of 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 are 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 antenna masts used for the U.S. Omega navigational system, the masts of Alpha must be very tall, for technical reasons. Unfortunately, no data are available for their height.

Some transmitters are being disabled as of January 2014.


A complete description of the Alfa Navigation System can be found on :


Material :

PC soundcard
Active antenna PA0RDT - see the antenna description here
Software : SDRSHARP  - download the software here