According to the article, that was dependent on the weather and the ocean. I'm aiming to go over land, including a small mountain range, in all weather.

Still, it's encouraging to read that at least one end of the link was not way up high, but rather at sea level. In my local testing, elevation was very important.

I saw HAM operators can go up to 10W of transmission power, but of course that would mean no encryption. ☹️