This paper presents the simulation results of the oscillation modes excited in the interaction space of an anode block of a magnetron and the azimuthal distributions of a longitudinal electric component of the RF field for either of the excited modes. Using CST code, there were considered available anode blocks with different configurations of the resonators: a rising sun anode block and a rising sun hole-and-slot anode block. The dispersion characteristics and distributions of the azimuthal components of the RF field for different geometrics of their cavities as applied to the X- and Ku-bands are given. The condition of acceptable separation both in frequency and in phase velocity between the operating JV/2 -mode (or 7T-mode) and neighboring (JV/2 - l)-mode has been determined. It suggested that the mechanism of forming the total RF field connects with possible interference of the RF fields excited severally in the resonant system consisting of the small and large cavities. The features design of the magnetrons with two energy outputs is presented, and their application in practice is determined. The results of the simulation are in good agreement with the experiment.