Category:CHN 4+4

Chinese 4+4 is a rather interesting and easily identifiable signal. It is most likely generated using an IFFT—much like the Clover-2000 waveform—as there is strong evidence to support this. When isolated within a channel, the modulation is not continuous (as is the case with conventional signals); instead, it features periodic drops to zero. These are not simple 180-degree phase shifts, but rather a specific generation method that allows for reliable, independent clocking of each individual channel. On the receiving end, an FFT is almost certainly employed. The generous frequency spacing is clearly designed to accommodate a modulation rate of 150 Hz.

Chinese Navy and Air Force use this modem

Sample of 4+4 (Q26 on 6516khz LSB)

Decoded result:

WXYXYXYXYXY HR TRY LL
NR968 CK156 35 1340 --

535 203 02326 004 773 318 353 246 351

MSG AGN

NR968 CK156 35 1340 --

535 20325 326 004 773 318 353 246 351

QSL?