Atmospheric Losses

where El is the angle of elevation. An effect known as atmospheric scintillation can also occur. This is a fading phenomenon, the fading period being several tens of seconds (Miya, 1981). It is caused by differences in the atmospheric refractive index, which in turn results in focusing and defocusing of the radio waves, which follow different ray paths through the atmosphere. It may be necessary to make an allowance for atmospheric scintillation, through the introduction of a fade margin in the link power-budget calculations.