If replacing your antenna lead doesn’t fix it, then it is somewhere ‘upstream’. Have others had the same problem? If yes, then unlikely to be your set or its antenna lead. How extensive is your building’s cabling? There may be problems with the junction points or intermediate amplifiers. (In our building, failure of the power point serving an amplifier blacked most or all of us out; replacement fixed the problem.) There are many other possibilities, and you will have to go through a systematic process of elimination.