RTÉ Radio is changing one of its FM frequencies in order to improve Radio 1 reception in the greater Belfast area and parts of the border region.
It follows criticism from some listeners in Northern Ireland who have relied on the medium wave transmitter, due to be switched off in ten days' time.
The decision to shut down the medium wave service was defended recently by RTÉ executives at the Joint Oireachtas Committee on Communications.
They were questioned about the position for listeners in Northern Ireland.
FM reception of RTÉ Radio 1 has up to now been poor in the greater Belfast area because of interference from a local transmitter.
From 9am this morning, Radio 1 is swapping frequencies with Lyric FM and will be broadcast on 87.8.
Listeners to Radio 1 in Louth and Monaghan along with the Belfast region, counties Armagh and Down should retune to that frequency.
The signal comes from the Clermont Cairn transmitter near Dundalk.
Radio 1 will continue to be available on long wave 252 and on the Internet.
