This book presents the basics of building various types of amplifiers, the most widely used in the composition of modern specialized radio receivers, as well as the principles of building digital radio receivers. The rapid development of modern telecommunications systems, aviation equipment, and space systems for various functional purposes, as well as new information technologies, is inextricably linked with the theory of building radio receivers. Radio receivers are an integral part of the radio line, which largely determine the quality of its operation, both in normal operating conditions and in a complex interference environment. Since the creation of the first lightning detector in 1895, the technique of radio receiving devices went a long way to the development of modern automated digital systems.