The mast head of yachts is obviously a good place to site antennae but there is not much space. When I installed my Simrad AIS I faced the problem of where to site an extra aerial. Andy at Greenham Marine suggested using the, then new to the market, Easy Split to share the AIS with the VHF. Yesterday I bought a new car stereo radio to replace the last one which had rusted away. It too can share the same aerial. A good piece of kit.
By the way, the shopkeepers in the Faroes are wonderful. The man in the Radio Shop gave me the Ipod lead free of charge and the following day made up a special lead to connect to the Easy Split and refused to take any money for it. Brilliant service.