|Enigma ID||M42 (catch-all MFA Moscow designator)||
|Emission mode||USB; MFSK-34, 40 Bd; OFDM-34, BPSK, 40 Bd; OFDM-34, QPSK, 40 Bd|
|Known counterpart stations|
Serdolik is a currently semi-retired proprietary full duplex ARQ system used by the Russian Ministry of Foreign Affairs. From the early 2000s until the mid 2010s, it served as their most common two-way HF mode, replacing Morse code and RTTY; it has since been replaced by "Perelivt". At present, only a few embassies continue using Serdolik.
Its main waveform is 34-tone MFSK modulated at 40 Bd, which offers a gross data rate of 200 bit/s. The modem also contains a 34-carrier OFDM waveform, modulated at 40 Bd using either BPSK or QPSK, which offers higher speeds of 1200 bit/s and 2400 bit/s respectively.
As Serdolik is a full duplex system, the MFA Moscow and embassy sides take different frequencies. The Moscow side is usually a lot more powerful, and it's not uncommon for the embassy to be inaudible.
- Serdolik HF communication system - JSC Sozvezdie [accessed May 31st, 2018]