VHF stands for Very High Frequency, which means your broadcasts travel pretty much in a straight line and don't bounce around the atmosphere (like shortwave signals) ... while the earth's surface curves and "dips" below the horizon. By Federal law VHF radios are limited to just 25 watts of transmitting power, because the line-of-sight limitation means your signal can't follow the earth's surface by wrapping around it. So more power doesn't translate to more range.
Which means you can expect to fire up your VHF and communicate with any vessel that's within 10-15 miles away.
Still loud n' clear? Now here's the bad news.
Uh Oh, I just punched a hole through my hull
Well ... then if things get hinky out of sight of land and a life-threatening emergency occurs, how can you depend on calling the Coast Guard for assistance ... if your signals won't even reach halfway to shore?
Useful Nfo You Should Know Department:
How far away is the horizon?
1.17 times the square root of your height of eye = Distance to the horizon in nautical miles
Example: Assume a 6-foot 3" tall man with eyes mounted 6 inches below the top of his head. Thus, 75" inches tall minus 6 = 69
√69 = 8.3066238629180748525842627449075
8.3066238629180748525842627449075 x 1.17 = 9.71875 nautical miles to the horizon
To convert from nautical to statute miles the factor 1.15 may be used (although it's not precise):
9.71875 nautical miles x 1.15 = 11.1765625 statute miles
See, there's nothing to it. :-(
