Which box do you have?
Are the channels still poor if you take the aerial out of the box and plug it directly into the TV? Bear in mind that TV tuners are usually better at pulling in signals than the box, so it might not pixilate as much as the box but still be evident.
Channel breakup can be down to the weather so how long has this been happening? It might be worth leaving for a couple of days to see if it improves.
If you experience issues with the picture on both your TV and Box then this points to an aerial issue and you will need to consult a local aerial installer.
If it's only the box affected, you could try a retune, but if it's a weather related issue, then you may find that not all channels will be available after the retune.
The next thing to try would be resetting your box. This differs between boxes so select your box and follow the instructions here.
https://help-centre.talktalk.co.uk/TV/Manage_my_TV_box/TV_Box_Maintenance_Reset
Please remember to mark Solved Posts with Best Answer. Doing so helps other customers and saves TalkTalk's Support Team time by only looking at unsolved topics. Thanks, Steve (a fellow customer).
