From West Marine
Expect 3 to 8 miles from Handheld VHF (lower power and lower height).
Expect 15 to 20 miles from Fixed VHF (higher power and transmitting from top of mast). - Link To: Selecting-a-VHF-Handheld-Radio
From the USCG: "Your VHF radio is intended mainly for short range communications, generally 5-10 miles, and at least 20 miles to a USCG station. To communicate at longer ranges, you will normally need a satellite telephone ...."
- Link To: US Coast Guard on Radio Telephones
The maximum range for VHF is limited by the curvature of the earth the same as for sight.
The range depends on the combined height of both your antenna and the other person's antenna. That is why USCG with a very high antenna on shore can communicate longer distances by VHF than your ship can communicate with other ships. Formula is stated by Wikipedia.
Because the formula includes a square root of the sum of the heights of the antennas, if you are using only a handheld to communicate with another handheld, you could increase range by taking one or both handhelds up sailboat masts. Doubling the combined height increases maximum range by 40%. On the other hand, it would be useless to climb the mast to communicate with USCG on shore because their antenna is so high that increasing your antenna height will not make a significant difference. Example: ((300+30)^0.5/(300+10)^0.5)-1 = only a 3% increase in theoretical maximum range.
The maximum range in Nautical Miles = 1.23 times the square root of the sum of H1 and H2 where H1 is height of your antenna and H2 is height of the other person's antenna.
If H1 = 10 feet and H2 = 10 feet then the MAXIMUM range is 5.5 nautical miles. For example, handheld VHF to handheld VHF.
If H1 = 30 feet and H2 = 300 feet then the MAXIMUM range is 22.3 nautical miles. For example, sailboat fixed VHF to UCSG with a tall antenna on a hill.
From the admiral's chair
John Berol is the husband of Captain Diane. He commissioned Celtic Song in 2005, has sailed extensively and maintains an active interest in both the boat and her captain. He believes the more you know, the better you will sail. The term “Admiral’s Chair” is a family joke. For just as every writer needs an editor, so every captain needs an admiral.