FM broadcasting
VHF Radio waves do not travel far beyond the visual horizon, so reception distances for FM stations are usually limited to 30–40 miles (50–65 km) They can also be blocked by hills or buildings.
Medium frequency
Radio waves at MF wavelengths propagate via ground waves and reflection from the ionosphere ( called skywaves). Ground waves follow the contour of the Earth. At these wavelengths they can bend (diffract) over hills, and travel beyond the visual horizon, although they may be blocked by mountain ranges. Typical MF radio stations can cover a radius of several hundred miles from the transmitter, with longer distances over water and damp earth. MF broadcasting stations use ground waves to cover their listening areas.