 "Tropo-scatter" happens when water droplets and dust particles refract a VHF/UHF signal over the horizon.Using relatively high power and a high gain antenna, this propagation will give marginal enhanced over-the-horizon VHF and UHF communications up to several hundred kilometers.During the 1970s commercial "scatter site" operators using huge parabolic antennas and high power used this mode successfully for telephone communications services into remote Alaska and Canadian northern communities.