Accelerating cavities of the modern superconducting accelerators operate with very high loaded quality factors. The detuning caused by microphonics, beam loading, and other external sources, can be as large as the bandwidth of the accelerating mode. The detuning results in parasitic amplitude and phase modulations of the accelerating field independent in each SRF cavity. The RF source must have sufficient rate dynamic control of the amplitude and phase of the RF field in each SRF cavity to maintain a stable accelerating field in the presence of such detuning. Methods of control of magnetrons with the required for SRF cavities rates are considered in this presentation basing on physics of magnetron operation modeled by the resonant interaction of the electrons grouped in "spokes" with the self-consisted field of the synchronous wave. Various experiments demonstrate behavior of the magnetrons in agreement with the model.