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AT-3104

AT-3104[1] is a proprietary HF modem, used primarily by the Russian Navy. It is the successor to the earlier AT-3004D.

AT-3104 is one of the traffic modes available for ship-to-shore links. When link setup is coordinated using Morse code, it is referred to as "QYT4."

12-carrier mode

AT-3004D and AT-3104 are nearly always seen transmitting using the 12-carrier PSK waveform. The supported data rates are 1200 bit/s (using BPSK) and 2400 bit/s (using QPSK). It has three identifiable conditions:

Condition Spectrogram Sample
Idle

Traffic

Standby

20-carrier mode

AT-3104 introduced an additional 20-carrier PSK waveform. However, it is very rarely used in practice.

Condition Spectrogram Sample
Traffic

Recording courtesy of Radioscanner

References

  1. КВ-модем АТ-3104