James,
Termination is definitely necessary with analogue (component and composite), not sure about SDi, but i dont tihnk so. Some monitors do have internal termination, but generally if they do it will be a switch you can turn off/on, usually saying something like 80ohm on/off. etc….. It actually says in the manual for my JVC1750 that if the output cable isnt connected the signal is automatically terminated, but i dont believe it as when you diconnect the lead, the luminance of the input signal jumps noticeably.
On other monitors that have a switch for internal termination, when both input and output leads are connected, AND the termination switch is on, the signal luminance drops! I would try a little BNC terminator to test, they arent particulalry expensive. Try cpc.co.uk.
Ref signals also need to be terminated, as they are essentially a composite signal.
cheers
NIck