The so-colled Echotel MAHRS 2400 is a 2400Bd PSK-8 serial waveform with simmetical 2 x 8 pre-tones in respect of the 1800Hz carrier. The signal has strong 106.66ms ACF spikes (256 tribit symbols) due to its frame structure: an initial 80 symbol (240 bit) preamble that is followed by a data block consisting of 176 data symbols (528 bit). The pronouncec BPSK states in the constellation plane are due to the BPSK modulation of the preambles (Figure 2).
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Fig. 1
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Fig. 2
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The waveform belongs to the Telefunken Racoms HF HRA 5100 radio communication, an ARQ-like system used in airborne platforms for air-to-air and air-to-ground comms. As far as is recoverable from the web, "MAHRS" (Multiple Adaptive HF Radio System) is the name of the HF radio-data standard originally developed by Telefunken, Arcotel is the radio processor and Echotel 1810 is the HF modem. The HRA 5100 system has been replaced by the more recent HRA 9100, both supplied by Elbit System (Figure 3).
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Fig. 3
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Yay. What software was used for the captures?
ReplyDeleteSA Signals Analyzer for the waveform, BEE Bit Editor for demodulated bitstream. The latter can be downloaded from the "Shack" page.
ReplyDelete