Category:Serdolik: Difference between revisions

Serdolik (Russian: Сердолик, English: Carnelian) is a proprietary communication system, used exclusively by the Russian diplomatic service. As of March 2020, the updated version of this system is deployed at the Russian embassies in Sofia, Dar es Salaam, and Nairobi.

Links are established by scanning 3 duplex channels in a loop, for 30 seconds each, until a timely response is received. On each frequency, a sequence of two tones is transmitted, representing the calling station's numeric address.

By default, an established link is in the command state, using 35-tone 40 Bd MFSK modulation. This state is used only briefly to switch between the different traffic speeds.

In the traffic state, 9 different speeds are supported. 200 to 1200 bit/s use MFSK modulation, while 2400 bit/s and up use OFDM instead. The symbol rate of all waveforms is 40 Bd.

Example recordings:

200 bit/sec mode transmission from Moscow

800 and 1200 bit/second modes test

Frequencies

bit/s	Tones per symbol	Spectrogram	Note
200	1		The most common mode
400	2		Testing mode
600	4		One of the most common medium speed modes
800	7		One of the most common high speed modes
1200	15		One of the most common high speed modes
2400	60xBPSK		Rarely used
3600	45xQPSK		Rarely used
4800	60xQPSK	Same as 2400 bit/s	Rarely used
7200	60x8PSK	Same as 2400 bit/s	Rarely used