Freeview viewers in parts of North-east Scotland and the Western Isles will need to retune their TV equipment on Wednesday, July 31 as local airwaves are cleared for the roll-out of faster mobile broadband.
Technical changes at the Durris, Knockmore, Rosemarkieand Skriaig transmitter groups will free up frequencies for the future introduction of fourth-generation mobile services.
Similar upgrades have already been carried out at a number of sites across the UK to prepare for 4G.
Around 129,000 homes in areas such as Peterhead, Banff, Inverness, Huntly, Elgin, Grantown on Spey and Dunvagen will be affected.
Programmes will be subject to disruption from midnight as channels including BBC One, STV, Channel 4, Channel 5, Film4, ITV4 and HD services are moved to new frequencies. Work at the main Knockmore and Rosemarkie transmitters is expected to be completed by 6am and viewers can retune at any point after this.
Services at some smaller local transmitters may be off-air until late afternoon. Once these resume, anyone missing channels should retune their TV or digital box to get them back.
Digital UK is launching an information campaign to make viewers aware of the need to retune, including local advertising and messages on screen.