The book provides the basics of the complex representation of random oscillations and the correlation theory of complex amplitudes of stationary random processes. Models of input radio signals are systematized. General methods of analysis of linear elements of radio devices under random impacts are described. Spectral characteristics of processes at the output of single-channel and multi-channel processes are determined and investigated. nonlinear devices. General methods of analysis are given and examples of calculation of characteristics of processes at the output of simple radio devices are given. Phase and frequency detectors and direction finding devices of various types are analyzed.