"Users of Freeview in most of north Wales will need to retune their equipment as changes are made to enable the spread of faster mobile internet access.
Television services will be disrupted as channels are moved to free up frequencies for the introduction of fourth generation (4G) mobile services.
Work at the main Moel-y-Parc and Llanddona transmitters was expected to be completed early on Wednesday.
Viewers can retune any time after this.
Services at local relay transmitters may be off air until late afternoon.
Under 4G, those using the internet on laptops, tablets and mobile phones should get browsing speeds comparable to those at home on fixed lines."
For the full story see http://www.bbc.co.uk/news/uk-wales-20323122