Secondly the next thing to check is whether the aerial cable is still attached to the TV Aerial Antenna . These are usually fixed on the chimney using a lashing kit and mast. Or the aerial & mast is fixed on a stand off bracket on the wall of the house. Finally the last place to check is in the loft. What you need to look for is any obvious damage or , such as the cable has come loose or the aerial antenna is in some way damaged or pointing in the wrong direction.
There is another DIY check that can be done if you have another working aerial socket in the home. If you have the extra TV point, then take the TV into that room and plug it in, if experiencing problems with it then it would definitely point to there being a problem with your Aerial Antenna. If not then it maybe just the aerial cable that is the cause of the interference. This maybe just a simple cabling replacement job, and you can avoid going to the expense of changing your whole TV digital aerial system.
At the end of the day there maybe nothing that can be detected through these checks and you would need the assistance of a qualified TV Aerial Installation Engineer to run a full test on the system using a spectrum analyzer. But if you have performed the checks mentioned above first you will rule out having to pay for a call out charge just for the aerial fitter to plug the aerial into the back of the TV.