14 October 2017

TADIRAN HF modem running in scrambler mode

TADIRAN HF modem, probably the HF-6000 model, running in COMSEC mode using FSK 125Bd/300Hz and scrambled voice-comms. Transmission heard on 5885.0 KHz/USB at 0755z with a very poor SNR. The sample marked as "A" is the "autocall" waveform: it precedes the MFSK/scrambler sessions, marked as "B", and terminates the link (Figure 1).
Fig. 1
The FSK segmentes sent during the scrambled voice-comms have a speed of 125Bd and 300Hz shift (same parameters of the MFSK-4 waveform):

Fig. 2

A distinctive feature of the FSK waveform is the TADIRAN "business card" that consists of a 84-bit period shown in Figure 3.

Fig. 3

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