VHF/UHF communications are usually “line-of-sight”. Transmitters and receivers don’t necessary have to be “visible” to each other, but the curvature of the earth causes VHF/UHF signals to not be receivable more than a few miles from the transmitter site, depending on how much power is being used.
But, sometimes the troposphere (the part of the atmosphere where our weather occurs) causes VHF/UHF signals to be bent back to earth over a much longer distance. That happened Saturday morning. A station in Seymour, Indiana running about 20 watts was able to easily access the amateur UHF repeater in Lexington, and we had a nice conversation. That is probably 100 air miles away, and is much farther than the normal communication distance for a repeater system such as the one we have here.