Sunday
May 1, 2016

# Homework Help: Science

Posted by Jenna on Sunday, February 18, 2007 at 6:36pm.

Could someone please explain to me in a simple way how FM, AM, and XM radio signals work? No one I ask seems to know.
Thanks for the help.

Radio waves are part of a general class of waves known as electromagnetic waves. In essence, they are electrical and magnetic energy which travels through space in the form of a wave. They are different from sound waves (which are pressure waves that travel through air or water, as an example) or ocean waves (similar to sound waves in water, but much lower in frequency and a LOT bigger). The wave part is similar, but the energy involved is electrical and magnetic, not mechanical.

Electromagnetic waves show up as many things: At certain frequencies, they show up as radio waves. At much higher frequencies, we call them infrared light. Still higher frequencies make up the spectrum known as visible light. This goes on up into ultraviolet light, and x-rays, things that radio engineers rarely have to worry about. For our discussions, we'll leave light to the physicists, and concentrate on radio waves.

Radio waves have two important characteristics that change. One is the amplitude, or strength of the wave. This is similar to how high the waves are coming into shore from the ocean. The bigger wave has a higher amplitude. The other thing is frequency. Frequency is how often the wave occurs at any point. The faster the wave repeats itself, the higher the frequency. Frequency is measured by the number of times in a second that the wave repeats itself. Old timers remember when frequency was described in units of cycles per second. In more recent times we have taken to using the simplified term of hertz (named after the guy who discovered radio waves). Metric prefixes are often used, so that 1000 hertz is a kilohertz, one million hertz is a megahertz, and so on.