Irish airspace
Firstly, as VHF transmissions are "line of sight", a receiver must be in a reasonable location, within approximately 50 miles of a ground transmitter, if the controller transmissions are to be received satisfactorily.
Obviously, aircraft transmissions are usually no problem for the same reason.
My friend lives in Killarney near some very high ground and I guess the reception is poor for this reason.
In the UK there are several publications giving the precise locations of NATS transmitters and the frequencies transmitted from each of them. I just thought there might be the same kind of publication available in the Republic of Ireland.