[tcmart14]

AM can be untrustworthy in mountains too. Many factors play in such as how the landscape is actually laid out, the make-up of the rock in the mountain. How signals bounce off the rock, etc. It for sure isn't fool proof. I wouldn't think that much better than AM unless your close to the tower. AM's big advantage is being able to travel farther on less power, but the low frequencies don't have good penetration power. This is why the Navy uses radios that runs on 900+ MHz for shipboard radio, 900 MHz (UHF range) has less distance, but better penetrating power through steel decks. Compared to frequencies that AM operates (HF range). Then there are atmospheric conditions and the cycle of the sun. At a solar maximum sure, but at a solar minimum, probably not.