11.2 A SUMMARY OF PROPAGATION TECHNIQUES
A radio communication system relies on one or more distinct propagation mechanisms by which electromagnetic energy travels from the transmitter to the receiver. These mechanisms are conventionally divided into three broad categories:
- Ground waves, which travel close to the Earth’s surface.
- Sky waves, which depend on refraction or reflection by the ionosphere.
- Scattered waves, which result from irregularities such as atmospheric turbulence or meteor trails.
Figure 11.2 summarizes the primary categories of radiated RF energy.
