Starting from the equations established by Agostinelli for the study of the wave surfaces in a electrically anisotropic plasma, in this paper we propose to investigate the propagation of plasma waves in a rarefied, radiative plasma, yet electrically anisotropic. In this first part, using the method of the small perturbations, we get, for the unknowns of the problem, a system of linearized equations and then we reduce the question to the consideration of three vectorial equations only in which the unknowns are: the velocity vector, the current density and the heat flux vector.