Hello Greg, I’m not an expert but I’ve seen lots of videos about this! There’s a type of antenna setup called “NVIS” which sends radio waves directly up, and when it bounces back it reaches a reliable radius of dozens of kilometers. I’ve seen someone testing this online and reaching more than 100km distance talking with a friend. NVIS circumvents any difficult terrain, as the radio waves are basically just going up and down, and not much horizontally. Best of luck!