21 June 2017

THALES HFXL modem, "SALAMANDRE" tests go on

Likely another "SALAMANDRE" test session for the new Thales HFXL modem spotted this morning on the 7MHz band. This time the modem uses 12 non-contiguous 3 kHz channels from 7505.8 KHz up to 7656.1 KHz (~150 KHz bandwidth). The HF waveform is a modified STANAG-4539 with the extended preamble of 124 symbols added by Thales developers; further info about the modified waveform and the modem, as well as useful links, can be read in this post.

Fig. 1
It's interesting to note in Figure 2 the use of a double 188-141A 2G link setup exchange before the beginning of the HFXL session: the ALE exchanges happen just on the first and last channel of the next HFXL transmission as to negotiate/announce the used band; anyway, the HFXL session starts after the usual 2G 3-way handshake (as in Fig. 1). This initial link setup part is termed by Thales as the "3KHz phase" and it is illustrated in one of their presentations
By the way, the used ALE calls are XLA and XLB and almost surely they stand for (HF)XL modem-A and modem-B and belongs to French Forces network.

Fig. 2
The HFXL modem 12 channels have been tracked using SDR-Console v3 software configured for twelve simultaneous receivers, in this sample all the channels exhibit a PSK-8 modulation at 2400 symbols/sec (Figs. 3,4): the channel #4 is damaged by an adiacente FSK-2 transmission.

Fig. 3
Fig. 4

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