A complaint of a particular channel breaking up is always put down to the aerial itself,where as in fact the fault lies with the TV and its pesky auto tuning service.
ideally thew aerial points at a particular transmitter,in theory that should be the only signals now received.
But in practice the aerial will receive other signals from different directions.Now auto systems on tv s aren't the brightest things ever created.
Sometimes a tuning system will give you a good BBC1 for arguments sake and then an itv coming from a side transmitter with poor quality or varying quality that break up and drops out.
So in many cases block the lower quality signals with a simple passive filter and bobs your uncle,retune and away you go.