Since the weak signal I asked my friend KarapuZ to send me one of his recordings of the Chinese MFSK-64 modem: it's easy to verify that both the records show the same start sequence of symbols (pic. 1).
 |
| pic.1 |
The signal, copied on 16990.2 KHz (cf) around 0910 UTC, consists of 64 tones, 37.5 Hz spaced, modulated alternatively at 37.5 and 18.7 symbols/sec speed (pic. 2 for 37.5 Bd speed).
 |
| pic.2 |
It's worth nothing the characteristic "dual-speed" modulation, seen in both the two recordings: in some segments the speed switches from 37.5 to 18.7 Baud and conversely (pics 3,4)
 |
| pic. 3 |
 |
| pic. 4 |
The initial part is always modulated at 18.7 Baud and - as said - seems to transport the same data (pic. 5):
 |
| pic. 5 |
https://yadi.sk/d/ZRGpFEoi3A9jkM
No comments:
Post a Comment