This transmitter in County Louth, was opened in 1981 to provide UHF television coverage for the North East of the Republic of Ireland, counties Louth, Meath, and North county Dublin. However with the site being less than 1 km from the border it was clear that this transmitter would be used to provide RTÉ services into Northern Ireland. Initially the two channels RTÉ 1 and RTÉ 2 were carried on Ch52 and Ch56 with TV3 (Ch66) and TG4 (Ch68) following later. In 1982, a 2M Amateur Radio Repeater was installed. FM radio transmission was also added providing coverage of the five national channels to a wide area.
In 2002 a new cable-stayed mast 120m tall was erected, this greatly improved coverage into Northern Ireland. The existing self-supporting tower was truncated, and is now only used for microwave links and the Amateur Radio Repeater.
In common with all other transmitters in Ireland, analogue television transmissions from this site ended on 24 October 2012, but uniquely Clermont Carn is the only main television transmitter in Ireland that is vertically polarised. Today the Irish digital television service Saorview is broadcast from here to a sizeable area including a large tract of Northern Ireland, with a good signal being received in Belfast and beyond. This overspill has been welcomed by the UK’s Ofcom who have provided information for viewers in Northern Ireland about receiving TG4 and the RTÉ channels, both from within Northern Ireland on the UK's Freeview service, and via the Saorview overspill.