Heard a weird modem status on 13536.0 USB – March 10, 2016
4x tone mode, ascending scale (1000Hz > 1525Hz > 2040Hz > 2630Hz approx), repeating again & again…
I’ve made a quick comparison with usual MHF-50 mFSK heard on the freq:
LEFT: MHF-50 mfsk – RIGHT: the stepping tones mode
each of the 4 tones are fitting fine with some MHF-50 tones, so it’s prob South African navy indeed..