All they had to hit was the power source. There were two masts, a sending mast made out of metal, and a receiving one made out of wood. It would surely have been easy to destroy the receiving mast. Alternatively they could just jam the radar either electronically (which they did do, apparently, later in the BoB) or with Window (which the Germans knew about but were afraid to use, lest it be used on them - a stupid argument if the Germans had won). Anything can be repaired, including the dams broken by the dam busters, are you saying that the dam buster raids were a waste of lives and resources because the dams were repaired during the war? All they had to do was knock out the radar masts or huts and control rooms in the SE of England, not the whole system, and if they were knocked out for most of the daylight hours then that was sufficient.