Scattering of a plane wave by mirror antennas with vibrating radiators is considered. The Fourier coefficients of the vector function equal to the current density on the mirror metal and the tangent component of the electrical vector on the geometric surface, complementing the surface of the mirror to close in some complete function system. Using these coefficients, the series for the given vector-function, converging to the L₂(S₀) surface norm, with each of the terms satisfying to the corresponding Meissner conditions on the boundary of the mirror is built. Using the found current on the mirror and well-known formulas, the dispersed field and differential diameter of dispersion of the mirror antenna are determined.