Digital modes... WeFax, Hellschreiber, a lot of RTTY
Fishing fleet stuff, numbers or encrypted letter/word groupings. Sometimes just general messages between folks on the boats or oil rigs and stuff.
Sometimes I'll hear a little PSK, and certainly there are Pactor style signals as well, but I have not gotten into decoding them yet.
Oh yea, HF USB from commercial airliners on the long hauls.
Poke around on the web to find something cool to listen to.
Utility News
Klingenfuss Hot Frequencies
Utility World
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