Thales HFXL modem tests spotted by my friend Geoff (who kindly sent me his recordings) on the upper limit of the 6 MHz band. In these tests the modem is able to use 16 contiguous(!) 3 kHz channels with 2 KHz spacing and occupies a bandwidth of about 80 KHz. As a rule, two stations are used.
Test transmissions consist of a series of 1300 ms bursts sent using the waveform STANAG-4539 (188-110B App.C) as modified by Thales by the add of their 124-symbol length extended preamble, ie the identification sign of the HFXL modem/waveform. Figure 1 shows the analysis of the upper channel and the Thales extended preamble.
Test transmissions consist of a series of 1300 ms bursts sent using the waveform STANAG-4539 (188-110B App.C) as modified by Thales by the add of their 124-symbol length extended preamble, ie the identification sign of the HFXL modem/waveform. Figure 1 shows the analysis of the upper channel and the Thales extended preamble.
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| Fig. 1 |
All the channels use PSK8 modulation at the symbol rate of 2400 Bd, user data rate is measured as 3200 bps with very short interleaver. Framing is the usual 287-symbol pattern of STANAG-4539: 256 (unknown) symbols for data followed by 31 (known) symbols for mini-probes (figure 2).
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| Fig. 2 |