How Does Radio Work?
Want to know know, how does radio work? Radio is pretty amazing. It can record someone's voice in one place and play that same voice through radio speakers for another person miles away, with no wires or any connection of any kind between the devices doing the recording and playback. What exactly is radio, though? How does radio work? To answer the second question, you need to know the already know the answer to the first, but don't worry--this article explains both in-depth.
First off, what is radio? As the name hints, radio is a form of radiation—electromagnetic radiation. Electromagnetic waves come in a variety of lengths; the entire spectrum includes electric waves, radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation. The longest waves are electric waves, followed by radio waves, and so on. Gamma waves are the shortest, too short to see, and of course electric waves are too long to see—in fact, light is the only visible wavelength. Since light and radio waves are the same thing, though—electromagnetic radiation--if radio waves were shorter, you would be able to see them.
Now that you know what radio waves are, take a look at what creates them. For radio to work, you need a transmitter to send out the radio waves, and a receiver to “catch” them. A radio transmitter creates electromagnetic waves of the right length—radio waves—and sends them out. If it's within range, a receiver will detect the radio waves, convert them into electrical signals, and then convert the electrical signals into sounds that will come out of your radio's speakers.
So how does radio carry the sound of a singer's voice, or spoken words, and not distort them? The primary job of the transmitter, besides sending radio waves out for receivers to “hear”, is to alter, or “modulate”, the waves to send a specific piece of information. Much like Morse code's combinations of dots and dashes to spell out words, modulation interrupts the radio waves at certain intervals so that they can carry messages and information to the receivers. Most information sent on radio waves is actually attached to the sidebands of the wave—higher or lower frequencies that travel on the original wave, which is called a carrier wave. This is done with a device in the transmitter called an oscillator, which combines the carrier wave and the waves of information so that they travel together to the receiver.
The radio waves made by your transmitter are sent out of your antenna, which amplifies them to be strong enough that they go out into space and are received by the satellites there. These satellites can bounce your radio waves back down to earth almost anywhere, which is why radio can be received from hundreds of miles away.
Once the radio waves reach a receiver—such as your radio—the device “demodulates” them, separating the signal information the original sender added from the carrier wave that the oscillator hooked it to. Once the signal information is separated, it's an easy task for the receiver to convert it into electrical signals and translate it into sounds that can be heard through your speakers.
That's how radio, without any wires or physical connection of any kind, can “hear” words spoken into a microphone in one place and make those same words in that same voice—that is, a precise electrical recreation of it, translated to electrical signals, then electromagnetic radiation, then electrical signals again—come out of speakers miles away.
The Columbia Encyclopedia, Sixth Edition. 2008.