I've messed off and on with ham radio for nearly a year now, and after listening to some of the Brine videos I've come to realize that a lot of them sound like a packet (more on packets: https://www.tapr.org/pr_intro.html and https://en.wikipedia.org/wiki/Packet_radio). Although it doesn't sound exactly like the same one from the Brine videos for here's a known packet for reference: http://www.sigidwiki.com/wiki/MOBITEX (mobitex 1200). I would like to say that my knowledge of ham radio is very poor, and therefore I don't know if the mode semi is using could actually be one that already exists which means it could be decoded, but if you're lucky sometimes in the chat on http://websdr.ewi.utwente.nl:8901, you can find people who know almost everything about ham and they could tell you if its a known mode or not. This part isn't all that related to the rest of my post but I just want to say that the definition of brine is a solution of salt in water, and the brine videos all have a white-noise in the background similar to the white-noise from radios, and since all the brine videos have a packet-like sound it would make since that the brine audio was transmitted from a pirate radio on a boat somewhere in the ocean.