Troposcatter

Tropospheric scatter (known as "troposcatter" among practitioners) is a method of transmitting and receiving microwave radio signals over considerable distances often up to 300 km. This method of propagation uses the tropospheric scatter phenomenon, where radio waves at particular frequencies are randomly scattered as they pass through the upper layers of the troposphere. Radio signals are transmitted in a tight beam aimed at the tropopause, midway between the transmitter and receiver sites; as the signals pass through the troposphere they are scattered, allowing the receiver station to pick up the signal. A related system is meteor burst communications, which uses the ionized trails of meteors to improve the strength of the scattering.