The distance that you can recieve/transmit on your VHF depends on two things.
1) The height of YOUR Aerial
2) The height of THEIR Aerial
Here is the formula for calculating the range of an antenna:
Square Root of Height Above Water (in feet) times 1.42 equals Range in Miles
Example: Highest point of your boat is 6 feet above water. You attach your 3-foot antenna at that point. The antenna is now 9 feet above water. The square root of 9 (which is 3) times 1.42 equals 4.26 miles
So how can you receive that marine radio weather broadcast that is 75 miles away? You have to perform this calculation for the "other" antenna also and add the 2 distances together to get the maximum range between the antennas. The weather transmission may be from an antenna several hundred feet high and on top of a mountain giving it enough range to connect to your antenna's 5 mile range. You would be able to communicate with a boat that was 10 miles away from you if it had an identical set up as you. Each of your antennas could "reach out" 5 miles.
So if you were both using a handheld radio at 5ft above the ground, you'd be able to transmit about 3 miles
Anyone know the height of a HMCG antenna?