Chapter 2 – Radio Propagation

Publisher Summary This chapter discusses various factors that affect the range of reliable radio communication. Propagation of electromagnetic waves is influenced by physical objects in and near the path of line-of-sight between transmitter and receiver. The first rough approximation of communication distance can be found by considering only the reflection of the transmitted signal from the Earth. If the communication system site can be classified, an empirically determined exponent can be used to estimate the path loss, and thus the range. When the transmitter or receiver is in motion, or surrounding objects are not static, the path loss varies and must be estimated statistically. Several techniques of diversity reception that can reduce the required power for a given reliability when the communication link is subject to fading are discussed. Noise is presented as the ultimate limitation on communication range. The chapter highlights that the noise sources to be contended with depend on the operating frequency. The importance of low-noise receiver design depends on the relative intensity of noise received by the antenna to the noise generated in the receiver.