Enigma ID M42 (catch-all MFA Moscow designator)

Spectrum image serdolik-spectrogram.png

Name Serdolik
Status Active
Voice N/A
Emission mode USB; MFSK-34, 40 Bd; OFDM-34, DBPSK, 40 Bd; OFDM-34, DQPSK, 40 Bd
Location Worldwide
Activity pages

Download audio sample

Known counterpart stations

Serdolik[1] is a currently semi-retired HF communication system. From the 1990s until early 2010s, it was the most common two-way mode used by MFA Moscow. During this time, it has undergone several upgrades, introducing automation and full-duplex ARQ features.

The startup mode is MFSK, running at 40 Bd and using 34 tones between 1410 and 2730 Hz inclusive, 40 Hz between each tone. 32 of the 34 tones represent 5-bit symbols, giving a gross data rate of 200 bit/s.

Serdolik also supports an OFDM mode, running at 40 Bd and using 34 carriers between 1250 and 2900 Hz inclusive, 50 Hz between each carrier, plus an extra unmodulated pilot tone at 1200 Hz. Carriers can be modulated using either DBPSK or DQPSK, giving net data rates of 1200 and 2400 bit/s respectively.

At present, Serdolik can be heard only several times a month, usually repeating ARQ control sequences without giving traffic.


  1. Serdolik HF communication system - JSC Sozvezdie [accessed May 31st, 2018]
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