Yesterday I was watching two large cruise ships sail down Southampton water (P&O ships,  'Artemis' and 'Aurora').   Both had a large wire antennas strung between the masts, and in the case of  Artemis this extended down at each end close to bow and stern; and there may even have been two wire side-by-side on this ship.  A really long antenna.   I'm not sure of the length of these ships, but they could  be 200 metres (ish), so even at the bottom end of HF these are electrically long-wires.   

Of course, the pair on Artemis, if I saw them correctly, could even be phased for really high gain at HF - a Rhombic perhaps?

 

Does anyone know if large modern ships still have MF, or a serious HF presence?  Or are the wire antenna(s ?) just there to hang flags from?  Or are they not even antennas, but just used for supporting decorations.

 

Artemis also had a mass of big whips on the bow, which I assume were base tuned HF - the normal VHF whips were practically invisible beside them.   Aurora presumably had something similar, but they weren't obvious.

 

Needless to say, each ship had two large VSAT radomes, and three or four smaller Inmarsat (and other satcom?) antennas.

 

Andy  G4JNT