If that over-the-horizon radar you installed in your garden isn't picking up incoming bombers like it used to, or if it keeps blowing the receive front end, it might be time to install a new TR cell (it switches the waveguide from receive to transmit). Here's some Scottish made Ferranti CV6169 WF471 TR cells. They probably cost the Royal Air Force a small fortune when new, but you can buy 'em here for an amazing bargain price.