This chapter is devoted to coders and modulators, which are important parts of modern radio receivers. Section 4.1 discusses the problems of transmitting radio signals using rectangular carrier sequence modulation in a mobile communication system radio channel with a limited bandwidth. First, methods for describing analog signals are discussed, and then, sequences of rectangular pulses are discussed. The requirements for the impulse response of filters in the transmitting/receiving RF front-end and the purpose of correcting their amplitude-frequency response are explained. Section 4.2 is devoted to the problems of signal sampling and encoding of speech signals. Definitions of analog, discrete, and digital signals are given, and their differences in the description in the time and frequency domains are explained. The methods of forming digital sequences for speech transmission, as well as the features of speech coding, channel coding, classification of noise-resistant codes, channel and block codes, the characteristics of convolutional codes, and multilevel coding, are explained. Section 4.3 discusses the methods of digital modulation of the most common radio signals. Waveforms of signals with frequency manipulation, including those with minimal phase shift, FMn signals with preliminary Gaussian filtering, and features of phase modulation/demodulation, with a description of various schemes of phase modulators, including binary and quadrature manipulation, are given. We pay great attention to manipulating the orthogonal frequency division of OFDM channels in the upward direction and on the downlink.