I bought a UHF/VHF TV aerial in Maplins (off Parnell St), for about Euro35.
I put it in the attic and brought the cable down to the kitchen TV. Reception of RTE1/1/TG4/TV3 is perfect. Can also get BBc1/2, ITV and Ch4 with varying degrees of snowyness, but certainly watchable. I am in Swords, so near enough to NI to pick these up.
Reception quality depends on where in the country you live, but most parts should have no problem with Irish channels, even without a booster.