The magnetron device is an electronic tube whose operating is based on electron movements in static orthogonal fields E and B. The cathode made from a massive copper block presenting resonator cavities is on of the main magnetron components. The cathode, as electrons source, is located concentrically in the middle region of the anode. The magnetron’s supply is ensured by feeding bars, while the power is extracted through an antenna coupled to one of the resonator cavities. The cathodes are classified as direct heating ones or indirect heating cathodes. The self-oscillations process of the magnetron is accomplished as the existing electrons generated by cathode provide energy, those electrons moving on within the interaction space towards the radio-frequency field. The thesis comprises a modest personal contribution of the author’s research in the light of theoretical aspects, experimental part and as application issues of the electromagnetic processes underlying the high power axial magnetron’s construction with vane resonator cavities and direct heating cathode, and, particularly, the 800-watt magnetron.