Freeview viewers in parts of the Western Isles may need to retune their TV equipment on September 20th to continue watching programmes.
Some Freeview channels are moving to new airwaves to allow for the future development of new mobile broadband services.
Following a decision by Ofcom, the media regulator, transmitters across the UK are being updated region by region as part of a major engineering programme being carried out between now and 2020.
Changes will begin at the Eitshal and Skriaig transmitter groups around 9am and Freeview services will be subject to disruption until mid-afternoon.
After this, any viewers who find they are missing channels can retune to get them back.
Homes receiving their TV signal from either the main Eitshal or Skriaig transmitters, or using satellite or cable TV, are not affected.
Around 7,000 homes are served by the affected transmitters.
Freeview will be running an information campaign to prepare people for the change, including advertising and on-screen messages.
Retuning should be straightforward and some TV equipment will retune automatically.
Anyone who needs advice, or who finds they are still missing services after retuning, can visit the Freeview website at: www.freeview.co.uk/tvchanges or contact the Freeview Advice Line free on 0808 100 0288.