On the basis of the elaborated one-dimensional analytical model of microwave radiation by an electronic beam with the virtual cathode is shown, that in reditron has a place spontaneous radiation, and in a vircator and a reflex triode-induced. However in last at the certain stage there is a failure of radiative instability owing to strong turbulence in an electronic flow. In this connection the idea is stated that this failure can be removed special profiling of front of a high-voltage pulse of a feed of the diode of the generator. Through an electromagnetic PIC-code the computer research offered by the authors vircator with internal TEM-feedback communication is carried out. The opportunity of effective management of output power through change of length of a feedback is shown.