Chapter List

Overview

Radio frequencies form a small part of a wide range of types of energy transmission by means of electromagnetic fields.

All forms of electromagnetic radiation into space are characterized by four common factors: their speed of propagation in free space is the same (300 10 ⁶ m/s), and they are subject, like light, to the laws of reflection, refraction and attenuation. The primary source of electromagnetic radiant energy is the sun. In this section we consider the small range of frequencies associated with broadcasting of television.

Clarke Maxwell indicated in 1864 that electromagnetic radiation could be established in space by electrical means. The physicist Hertz, in 1887, proved experimentally that electromagnetic fields could be set up in space and detected, as Maxwell had predicted. He also showed that such radiation obeyed the same laws as determine the behaviour of light. At a time when intercity and intercontinental communications were carried out by means of wire links, Marconi saw that this radiation provided the possibility for a 'wireless' means of communication. He put together a communication system consisting of...