An abreviated explanation. You have your airport/departure/arrival frequencies. Then you have your en route frequencies.
The first are typically located nearby the airport, and if you're close you can hear the ground TX and the aircraft.
For enroute, the ground TX sites are all over the place. I put the 125.075 in the search and it might be a TX site out of Zanesville, OH. Depending on where you are in OH, Indianapolis Center or Cleveland Center control the enroute. You can go through radioreference and see if you have any sites close by.