The Complete Handbook of Radios

Chapter 1: Understanding Radios

A radio is a tool for moving information through space without a physical conductor. Strip away the consumer marketing, the hobbyist mystique, and the acronym soup, and you are left with a remarkably simple transaction: a transmitter converts an electrical signal into an electromagnetic wave, that wave travels through the air (and sometimes through walls, buildings, or vacuum), and a receiver captures a tiny fraction of that wave and converts it back into an electrical signal. Every radio on the market, from a $20 walkie-talkie to a $10,000 base station, is an engineering implementation of that single idea. If you understand the fundamental transaction, you will be able to evaluate, install, and troubleshoot any radio equipment you encounter.

The Electromagnetic Foundation The wave that carries the information is called electromagnetic radiation. It is the same phenomenon as light, but at a different frequency. When you tune a radio, you are selecting a specific frequency, measured in hertz (Hz), which counts how many times the wave oscillates per second. Your FM broadcast radio receives signals around 100 megahertz (MHz), meaning the wave oscillates one hundred million times per second. A two-way radio operating at 450 MHz oscillates faster still. Your cell phone uses frequencies around 1,900 MHz to 2,200 MHz. This difference in frequency has direct and practical consequences for how far a signal travels, how well it penetrates buildings, and how large the antenna must be.

Here is a rough rule of thumb: the lower the