the statement that you need a license if you are using the vessel commercially is not exactly accurate. you MAY need a license if you are using your vessel commercially.
check out this page -
http://wireless.fcc.gov/commoperators/mp.html
which states in short -
MPs are required to operate radiotelephone stations aboard certain vessels that sail the Great Lakes. They are also required to operate radiotelephone stations aboard vessels of more than 300 gross tons and vessels which carry more than six passengers for hire in the open sea or any tidewater area of the United States. They are also required to operate certain aviation radiotelephone stations and certain coast radiotelephone stations.
so in the arena of "commercial", most 6-pak charter boats aren't required to have one (if you are more than 300 gross tons, you are probably carrying more than 6 passengers!), nor are many commercial fishing vessels.
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Capt. Adam
Karen Ann II