I'm not a controller, but surely if you have a large metal object creating a permanent echo, you can't see anything behind it?
Static objects aren't a problem, and ducting and other techniques allows cover beyond them. They can be taken out using MTI, as can moving objects using doppler MTI.
The problem with windfarms is the rotating blades which produce variable returns which are more difficult to handle. However, techniques to handle the problem have been demonstrated, and are presumably employed by the TPS-77.
I'm just shocked that we've reached the stage that the AD radar cover for the UK has to be paid for by energy companies owned by the French etc...
