20 May 2017

Unid 2400Bd QPSK burst system


This mode employ 4-ary phase-shift keying (QPSK) on a single 1800 Hz carrier as the modulation technique for data transmission, the modulation of the carrier is a constant 2400 symbols/sec waveform.

Fig. 1
Each transmission consists of four 870 ms bursts each composed of a preamble followed by 21 data blocks (Figure 2); each data block is composed of 90 QPSK symbols: 31 known symbols probe followed by 59 (unknown) data symbols (Figs 3,4).

Fig. 2
Fig. 3
Fig. 4
These transmissions have been heard up & running for some hours on 10410.0 KHz/USB on 18 May morning, sometimes a second station has been heard working in a ARQ-like mode (Fig. 5).

Fig. 5
No idea about the source and the name of such system.
Other unid transmissions using QPSK bursts modulated at 2400 symbols/sec are discussed here:
http://i56578-swl.blogspot.it/2016/08/unid-qpsk-2400bd-single-tone-burst.html
http://i56578-swl.blogspot.it/2016/07/unid-qpsk-2400bd-1125ms-acf.html

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The same transmissions have been heard also by cryptomatser and are discussed in radioscanner.ru forum by him and KarapuZ,  here the link:
Http://www.radioscanner.ru/forum/index.php?action=search&loc=1&forum=21&topic=39959&page=1319757


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