CB Radio, Frequencies, Channels, & Modulation

The world of CB radios (Citizen Band Radios) is both the same and different from standard car and home radios. For instance, both have AM and FM bands and work through many frequencies. Yet, CB Radio technology takes those concepts one step further for transmission and receipt of voice communications.

Combination of Three Elements

This is done through three elements critical to CB Radios – frequencies, channels, and modulation. Without these, transmissions couldn’t be received or sent across various distances. And while some people think these are synonyms of one element, they are three individual properties.

Today, we’ll break down each one and how they work in the CB Radio universe.

Frequencies

Most countries have allocated frequencies for CB Radios between 26.96 and 27.4 Megahertz (MHz). Breaking it down further, each radio wave has a frequency of approximately 27 million cycles per second. In other words, 27 million waves, each 11 meters long, radiates from your antenna each second. And it does so at the speed of light.

Modulation

When you speak into a CB microphone, your voice hitches a ride on a radio wave through a form of modulation. The most common in the Americas are ones you know from commercial radio – Amplitude Modulation (AM) and Frequency Modulation (FM). While not as popular as it was during the first half of the 20^th century, AM is still regularly used in CB Radios.

Some radio models also offer a more compact form of AM called Single Side Band (SSB). This modulation offers up to two times the range of AM and FM signals. Additionally, each SSB has two channels:  an Upper Side Band (USB) and Lower Side Band (LSB). 

Channels

The Americas and Great Britain, among other countries, allocate a total of 40 CB channels for use in the 27 MHz band. Most of these are available for communication on a first-come, first-serve basis. However, there are some channels reserved for other purposes.

For example, Channel 9 is reserved for emergency communications. When populated, it is recommended to keep channels above and below it free for overflow. Channels 16 & 19 are known as Traveler’s Channels. They are used by truckers and others to keep track of traffic, weather, and where Smokey (the police) may be hiding.

You can get additional feedback on the above information by speaking with the staff at CB Radio Supply. They can walk you through operations and what type of radio may work for you.