First of all you need to buy the good quality cable. If your cable is already old then it is the golden chance of replacing the cable with the new one. Remember usually the cheap installer tries to fix the existing cable and after some time it breaks again. So I would recommend you to get the new cable and then install with your set up. For finding the best solution of this problem you may call the https://tv-aerials-uk.co.uk/.
The damage of the cable means the water starts entering in the cable and could damage your TV or other electric system. I would recommend you if you noticed your cable is damaged then instantly disconnect everything with your cable and put in the small container. For this task please cover your hands with gloves and wear rubber chappal in your feet. If your connectors are damaged only then you can replace them with new ones otherwise you can fix them. For changing the cable you can either do it yourself otherwise it would be much better if you hire the professional for this task.
