6 months ago all my local channels were at 100% with my 14 month old Winegard 9095 antennae ( 60 mi. ) directional. 3 months ago it began fading to no picture. Channels 4 & 5 are still 90 and 100%.....if all stations are coming from MT. Wilson 336 degrees, how do some come in and others do not ?? I've changed coax cables, hi def Direct TV receiver, 75 ohm transformer, elements are all straight. Terrain is flat with a few trees 150 yds away and have always been there. I have also moved the antennae all along the rooftop any ideas ?