Freeview viewers in much of West Sussex may need to retune their TV equipment on Wednesday next week (March 21) to continue watching some programmes.
Some Freeview channels are moving to new airwaves to allow for the future development of new mobile broadband services.
Following a decision by Government, transmitters across the UK are being updated region by region as part of a major engineering programme being carried out between now and 2020.
The required changes will begin at the Midhurst transmitter group shortly after midnight and some Freeview channels will be off-air overnight until 6am.
After this, any viewers receiving their TV signal from the main Midhurst transmitter who find they are missing channels can retune.
Services from smaller local transmitters will be subject to disruption until later in the day. Satellite and cable TV are not affected.
Around 90,000 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.
Further changes will take place next year as engineering work is completed in neighbouring areas.
Any viewers affected will see reminders to retune on their TV screens.
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.
Some older aerials may need to be replaced to continue receiving all channels. Help may be available for viewers where this is the case.
Equipment for other services that use Freeview channels, such as YouView, BT TV, TalkTalk, EE and Now TV may also need to be retuned.