In wireless communication systems, an RF signal generated by a transmitter is sent into free space and eventually picked up by a receiver. The interface between the transmitter and free space and between free space and the receiver is the antenna.

The incredible variety of antenna types used in radio communication are all based on a few key concepts. This chapter introduces all the most popular and widely used antennas in HF, VHF, and UHF applications. Microwave antennas are covered in Chap. 16. Also discussed are the characteristics of free space and its ability to propagate signals over long distances. A study of wave propagation— how radio signals are affected by the earth and space in moving from transmitting antenna to receiving antenna—is critical to understanding how to ensure reliable communication over the desired distance at specific frequencies.