Formerjock--
I am not familiar with the geology around Tennessee. Is it flat with a lot of prairie land (like the Upper Midwest) or mountainous like it is out here?
Some of the personal FM transmitters, particularly older models, can actually throw out a rather impressive signal for the type of devices they are. When I was still living in the building in downtown Portland, seven storeys up, I used to use a Belkin FM transmitter (forget which model, but it was white and had a digital readout and push-buttons on its tuner.) It was connected to my VCR which was tuned to the SAP on channel 10 (OPB), and I could throw out the Golden Hours radio reading service from it for at least a good mile in any direction, more or less. I could certainly hear it clearly at my then-workplace, about three blocks west.
This was downtown in a major city (lots of buildings all around), in an area that's quite hilly and in the foothills of the Cascades yet. If your area's flat such a signal could propagate even further.
That's just my hypothesis, anyways.