How russian navy jams international distress channels

Not a new logging this time, but a cautionary tale about stupid and irresponsible using of the HF resource by armed forces of the country where such behaviour is a style of life over the centuries. That’s why I decided to use screenshots from remote SDRs to illustrate the fragrant cases of GMDSS channels jamming.

There is a set of frequencies allocated for GMDSS (Global Maritime Distress and Safety System) on MF and HF bands for short- and long-distance distress calls:

Band            For voice calls:        For DSC (digital selective calling) signals:

MF              2182.0  kHz             2187.5  kHz
HF 4  MHz       4125.0  kHz             4207.5  kHz
HF 6  MHz       6215.0  kHz             6312.0  kHz
HF 8  MHz       8291.0  kHz             8414.5  kHz
HF 12 MHz       12290.0 kHz             12577.0 kHz
HF 16 MHz       16420.0 kHz             16804.5 kHz

All the channels are designated for emergency communication by international agreement and being monitored by the Maritime Rescue Coordination Centres all over the world. They must be kept clear of other QRMing signals.

However, not all countries follow the international agreements, endangering the lives of people across the seas and oceans. They make interference on the mentioned frequencies now and then, as it can be seen on the following screenshot made on 11^th of August 2019 at about 17.30 UTC:

Here is typical CIS-12 (aka FIRE, MS5) PSK signal on 6311 kHz produced by AT-3004D and AT-3104D military 12-tone multi-channel modems used by russian armed forces. One can see a characteristic carrier (pilot-tone) on 6314.3 kHz as well as 12 subcarriers with 200 Hz spacing between them. The wideband CIS-12 signal is interfering with DSC call of more narrow spectrum which is also visible under CIS-12 on the distress frequency of 6312 kHz.

TDoA analysis showed that source of the signal is located in North Sea, between U.K., Denmark and Norway. That was some warship with approximate coordinates of 56.65 N, 02.05 E:

The Twente University web-SDR in Enschede has a great feature to store 24 hours waterfall for entire 0 to 29160 kHz frequency spectrum daily. It’s a good opportunity to check some signal’s history for some concrete day. The following screenshot demonstrates dynamics of evening signals strength on 5900 – 6550 kHz frequency range. The CIS-12 signal on 6311 kHz is marked by red arrow and red strips at the beginning and end of jamming period.

So, one can see that the jamming of the international distress channel started at about 14.40 UTC, stopped at 18.20 UTC approximately and lasted for about 4 hours:

6 MHz HF DSC channel is still in use in European countries, including northern part of the continent. According to the loggings from DXers in Classaxe Database, these European MRCCs were active on 6312 kHz in year 2019:

DSC ID         Station                             ITU    Last Logged
002070810      Varna Radio                         BUL    2019-08-21
002371000      Olympia Radio                       GRC    2019-08-21
002387010      Rijeka Radio                        HRV    2019-07-16
002392000      Piraeus Radio                       GRC    2019-02-07
002640570      Constanta Radio                     ROU    2019-07-15
002734417      Kalinigrad Radio                    KAL    2019-03-27
002750100      Rig Rescue Radio                    LVA    2019-05-18
002770330      Klaipeda RCC                        LTU    2019-05-18
219015591      Sailor Examiner XPE3307 Pandrup     DNK    2019-07-17
219016306      Simac-1 XPE3817 Svendborg           DNK    2019-03-18
228040600      Test ANFR SR Donges                 F      2019-08-13

By the way, this is not only case of distress channels jamming. The similar interference was also observed on the voice call frequency of 6215 kHz on 23^rd of April 2019 at 18.10 UTC (thanks to my DX-colleague Ray from France for this screenshot from Twente University web-SDR):

Here is the same CIS-12 mode signal of russian military modem on 6213 kHz. Unfortunately, the TDoA analysis was not fulfilled that time. The jamming took place from about 14.40 till 15.20 UTC and from about 17.30 till 19.05 UTC that day:

Conclusion: there are two ways to stop such dirty tricks in light of recent events: 1) to impose more and more new serious sanctions which will destroy putin’s criminal regime and his army of malicious fools; 2) to wait till the russian armed forces destroy themselves in future military exercises.