Thales HDR Single Tone modem? (TRC-3600/3700 family)

 

I rcently spent a bit of time monitoring the data transfer sessions which frequently happen on 6478.0 KHz/usb in ARQ mode. As usual, transfers start with the link setup stage: the particular and distinguishable shape of the ALE burts makes it possible to identify the Thales Systeme-3000 Skymaster ALE. The initial part of the ALE burts is SDPSK (Symmerical Differential PSK) modulated at 2000 Baud speed with a carrier frequency of 1600 Hz; as you see, transitions do not traverse the origin and the information is stored in the transitions and not in the states (figure 1). The initial part is followed by short MFSK-8  125 Baud segment that is not compatible with MS 188-141 2G-ALE although the scope be the same (they use different tones library).

Fig. 1 - Systeme-3000 Skymaster ALE

The SDPSK part exhibits a 50ms ACF that corresponds to a 100-bit frame (figure 2)

Fig. 2

Data bursts are PSK-8 modulated at a symbol rate of 2400 Bd and exhibt a 106.6 msec ACF (corresponding to 256 symbols) but adopt diferent frame structures: likely it's due the the adaptive feature of the modem which therefore adopts different data rates and waveforms (figs 3,4).

Fig. 3

Fig. 4

The presence of the Systeme-3000 ALE bursts - and thus a Thales proprietary waveform - suggest that the 2440Bd/PSK8 waveforms (used for data) are sourced by the High Data Rate modem incorporated into the TRC-3600/3700 family of combat radios. Quoting TRC-3600 datasheet: "It integrates a high data rate, multiwaveform, single tone modem (from 75 to 5400 bps) and a vocoder (800 - 2400 bps) associated to a high security digital COMSEC chip. The performances of the modem, the use of powerful error correction codes and the use of real time adaptive procedures enable to offer reliable HF links even on a severely degraded ionospheric path. The links are automatically optimized in real time according to the possibilities of the HF channel".

...and yes, yet another 106.6 ms ACF waveform.

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