HAM or Amatuer radio works just like a cell phone or wifi device. It uses RF energy to transmit data over the airwaves. Most commonly, people think of HAM radio as people talking to other people, but it can be for transmitting anything. including transmitting data. Data can be modulated onto RF waves across most spectrums and broadcast out for anyone to receive. With some basic equipment, you can send and receive text messages OTA (over the air). Since you can send text, you can send anything really since text is just a representation of binary combinations. In the video I previous linked, @nvk demonstrated sending a bitcoin transaction OTA. Which is then broadcast on the internet using normal bitcoin channels over the internet. This could be email traffic or other data. Amatuer radio is generally regulated to certain bands and frequencies based on geographic justrisdiction, but with certain bands and equipment, I could talk across the world.

Combining amature radio with bitcoin seems ripe to make the protocol more censorship resistant.