unid 200Bd/400 MFSK-4

Yet another interesting signal sent me by my friend Eddy from Australia. The transmission has been recorded on 16320.0 KHz/USB at 0520Z and consists of 200Bd/400 FSK-4 segments (the signal in between does not carry information). Figure 1 shows the measurement of the relevant FSK parameters. 

Fig. 1

The first two segments A,B (the shorter ones) could probably act as selcall. Indeed, after the removal of the polynomial x^5+x^4+x+1, the stream exhibits an interesting 8-bit structure where repeated initial patterns can be seen.

Fig. 2

The longest segment has an interesting structure. In my opinion, the initial part is formed of a 118-bit initial sequence followed by a block consisting of a 24-byte sequence which is four times repeated. 

Fig. 3

After the removal of the initial part, the stream shows a 504-bit period but with several alternate sequences (Fig. 4). The same 8-bit structure is visible after the removal of the polynomial x^5+x^4+x+1 (Fig. 5 ). Most likely it's a Chinese waveform, although there are not more informations about it. Recently these transmissions have also been listened on the Twente websdr (and just on the same frequency).

Fig. 4

Fig. 5