More than 650,000 homes will be covered by the move, with many more in the Irish Republic.
At midnight, Olympic champion Dame Mary Peters will bring 50 years of analogue TV services in Northern Ireland to a close and switch on a new high-power digital TV transmission service by Arqiva.
During the following day, main stations at Divis, Brougher Mountain, Limavady and 43 relay transmitters across Northern Ireland will switch to a new high-power DTT system.
John Cresswell, CEO of Arqiva, said: “The completion of DSO in October will signal the end of what is a truly magnificent achievement for Arqiva and our Freeview partners, alongside Digital UK and Ofcom. In only five years, we have transformed this vital public service and built a modern platform for transmitting the best of British TV into over 20 million homes across the UK. Along with the launch of YouView, DSO, by providing digital television across the UK, cements 2012 as a landmark year in British broadcasting keeping free-to-air viewing for consumers, at its core.”
A special programme will be broadcast jointly by the BBC and commercial station UTV marking 50 years of analogue broadcasts. It will be presented by TV personality Eamonn Holmes.