Technical informations - Systems

4 + 4
Caratteristiche principali : 2 gruppi di 4 canali spaziati di 300 Hz, spaziatura tra i due gruppi di 400 Hz. Alcuni "Utility Listeners" ritengono si tratti di un sistema Cinese Frequenze in kHz : 6874, 7628, 7755, 7840, 7845, 7855, 7888, 8060, 9060, 11160, 10806.5, 14835, 16270, 17430, 18320. Canalizzazione e frequenza centrale
 ch         1    2     3     4     5     6     7     8     
 CF Hz     615  915  1215  1515  1965  2265  2565  2865

4 + 4
This is an 8 tone MFSK signal with a unique tone arrangement. It is a Chinese Diplo system with most traffic originating from Peking. Its real name and base modulation mode (FSK/PSK) are unknown although analysis suggests that each of the 8 channels is 150bd or 75bd synchronous FSK. No estimation of total baud rate. The tones are grouped in sets of 4 spaced 300Hz apart with a 450Hz intergroup gap, 4 tones w/300Hz spacing, 450Hz gap, 4 tones w/300Hz spacing. Most 4+4 signals seem to be centered on .74. For an example try the signal centered on 8321.74:


Il sistema 4 + 4 in ciclo di IDLE


Il sistema 4 + 4 in trasmissione