Helicomparator
Considering that we are talking about the state of things 50 years ago I think you could cut the dear old Wessex III a bit of slack. It had a few shortcomings for sure but even the digital systems we use today have shortcomings too.
By the way it was a duplex system. The Sea King was simplex. The problem with calm sea was easily dealt with by taking out the cyclic channel and trimming the airspeed back using the same 'D' as the normal programme, then when you get to 40 feet keep the speed coming back until you caught up with the downwash and generated your own doppler signal. The height-smoother in the rad alt hold took care of 'normal' sea states but when the waves get to 30 feet you are always going to get a bit of hunting. Never had a problem of being too high - A/S Wessex pilots tend to get nose-bleeds above 500 feet anyway.
I have a copy of a speech made by the Head of the CAA in about 1975 in which he praises the helicopter services provided to the offshore community and comments that to succeed they had to follow military standards. (there were no comparable performance standards in the UK in those days).
G.