Chapter Overview
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.
Chapter Outline
14-1 Antenna Fundamentals
14-2 Common Antenna Types
14-3 Radio Wave Propagation
Chapter Objectives
- Describe the characteristics of a radio wave.
- Compute the length of one-quarter wavelength and one-half wavelength antennas, given frequency of operation.
- Name the basic antenna types and give the characteristics of each.
- Explain how arrays are used to create directivity and gain.
- Describe ways in which antenna design can be modified to produce an optimal match between the impedances of a transmitter and an antenna.
- Describe the characteristics of ground waves, sky waves, and space waves.
- Compute signal strength.
- Define fading and diversity reception.