The propagation of radio waves by scattering as a result of irregularities or discontinuities in the physical properties of the troposphere. 2. A method of transhorizon communications using frequencies from approximately 350 MHz to approximately 8400 MHz. Note: The propagation mechanism is still not fully understood, though it includes several distinguishable but changeable mechanisms such as propagation by means of random reflections and scattering from irregularities in the dielectric gradient density of the troposphere, smooth-Earth diffraction, and diffraction over isolated obstacles (knife-edge diffraction. ) Synonym troposcatter.