Chinese CODAN intruding into the 40m band

[VK3RX]

Posted on the Radio Reference forum by KA3JJZ:

From Ary Boender in the UDXF- the list of logs is too long to post here, but here's the test. Any transcription errors are mine...

Since mid 2016 I logged CODAN selcalls on 7, 8, 11 and 13 MHz. Until a week ago I didn't know who they are. Australian State Emergency Services was suggested but there are too many stations and they are also transmitting 24/7. That doesn't fit the SES activities. Besides that SES and affiliated service do not use these frequencies. So, if it isn't the SES, what is it???

It appears to be a HF Vehicle Tracking System. The syatem is used by companies in various countries, but the specific traffic that I heard all come from one place: the Spratley Islands in the South China Sea. China is building artificial islands in the Fiery Cross Reef. The Chinese started their activities in 2015. The first transmissions from that area were noticed in early 2016. The tracking system uses CODAN equipment that sends selcalls to base stations. The base stations use the received data to track the ships, barges and cars used for the building activities. Sometimes GPS data is mentioned in the CODAN messages, but so far I have no idea how to read it.

Voice traffic has been heard in Mandarin following CODAN calls. These are actual calls, not the tracking devices. They are answered by the reverted tones sent by the receiver's CODAN radio to acknowledge the receipt of the signal.

Base stations IDs include: 1111, 2222, 3333, 4444, 5555, 6666, 7777, 8888, 1188, 6363, 6969, 7474, 7979, 9898, etc. Note the combinations: either XXXX or XXYY or XYXY. Easy to recognize. These IDs are in the "TO" field.

Frequencies in USB. The center frequency is 1785Hz higher.

7103, 7106, 7109, 7112, 7121, 7124, 7127, 7130, 7133, 7139, 7142, 7145, 7148, 7157, 7160, 7918, 7921, 7933, 7936, 7938, 8003, 8006, 8009, 8012, 8015, 8021, 8024, 8027, 8030, 8033, 8041, 8066, 8072, 8075, 8078, 8596, 9047, 9090, 11149, 11159, 11163, 11168, 13431, 13452 kHz and maybe more.

The Chinese are intruding the 7MHz HAM bands with this service.

Examples of GPS data:
ESN 117117
ESN 117255