If everything looks fine behind the TV, grab a ladder and head outside. Loose connections and damaged antenna elements will be readily obvious by a visual inspection. Make certain that all connections and fasteners are tight and secure. Look for frayed wires, corrosion, or other evidence of deterioration. Check the orientation of the antenna.
Windstorms can blow the antenna out of proper alignment.
Breaks or short circuits in a transmission line will cause a reduction of signal strength. Lines that are loose from their fastenings may swing against other objects causing changes in the picture intensity. Secure the transmission line and repair any chaffing. Replace the transmission line if it is in bad shape. Wind, hail, and ice are the most common cause of damaged antenna elements.