Ham radio can be used to receive encrypted messages, so it can be used to send and receive bitcoins over very long distances.
Imagine a scenario in the future where only Brazil has internet as we know it today and allows bitcoin to be used.
We could use ham radio using encrypted communications for bitcoin sweep.
Then again, ham radio communication seems easier to restrict than the internet.
By the way, do you think in such scenario would be possible to use an old fashioned modem to connect with internet in Brazil using ham radio?