Saorview users in some areas of South Wicklow have been advised to retune their set-top box by November 7 or risk losing the service.
Viewers in the Mount Leinster transmitter region will need to retune their Saorview televisions or boxes ahead of the launch of the new RTE 1 HD channel in the new year.
Users need to carry out the retuning even if they do not have a HD TV, or risk losing the service in the coming weeks.
More than 600,000 Saorview users are affected nationwide including viewers in the Clermont Carn transmitter region in the north east of the country.
Counties affected include Louth, Meath, North Dublin, Cavan, Monaghan, Down, Armagh, Antrim, Wexford, Carlow, Kilkenny, Laois, Offaly, Tipperary, Waterford and Wicklow.
“It will be very straightforward for most people and takes five minutes,” Saorview digital reception manager Brian Geraghty told RTÉ Radio yesterday.
Anyone who encounters any problems retuning their service is asked to call the Saorview helpline on 1890 222 012 or log on to www.saorview.ie.