VHF radios are used to communicate from boat to boat. VHF radios use FM radio waves to pass information back and forth. FM radio waves operate by "line of sight," meaning the sound wave is sent in a horizontal pattern from one radio to the other. This works fine for most marine applications, but the sound waves cannot penetrate through tall objects.
(Think of how your radio cracks up when you are in the mountainsâ€¦.the cracking noise is caused by the radio waves not being able to penetrate through the mountains, so what you are hearing are the pieces of the waves that make it around the mountain)
Self-contained (radio comes with the antenna and there is no need for a mount) Used for short range use: 5 watts, 5 mile range.
Fixed Mount VHF
Requires all 3 individual components: radio, antenna, and mount. Used for long range use (open ocean): 25 watts, 25 mile range. The longer the antenna, the better (obstructions, especially in open sea, can block the pathway of the signal, so the taller the better.)