The method of physical optics is employed to analyze the major electrodynamics characteristics of a reflector antenna in a form of a parabolic cylinder, which is irradiated by the field of a filament of an in phase magnetic current, and a spherical reflector, which is irradiated by the field of a Hertzian horizontal dipole. The irradiator field is written in an explicit form and can be calculated with a prescribed accuracy in an arbitrary space point, including the case of small electrical dimensions of the focal distance. Proceeding from the above, an influence of the effects of the irradiator's near zone on the results of calculating the radiation pattern of a reflector antenna was analyzed.