Although it may seem a bit outdated now, the invention of the common radio revolutionized modern society when they were first invented over a century ago. Despite the widespread use of this technology, most people don’t have the slightest idea how these extremely useful little appliances actually work. Here’s an overview for anyone who might be curious:

Radios were invented to make use of radio waves, which at this point have enabled the speedy airborne transfer of music, conversations, pictures and data over millions of miles. Everything from your AM and FM radio to your cell phone to your WiFi to your GPS uses radio waves in order to function. Radio waves can also be used for non-broadcasting purposes, as any microwave oven proves. But for now, we’ll stick to conventional radios.

At its base, radio wave technology is extremely simple. You can create an extremely simple radio transmitter simply by tapping a coin against a 9-volt battery; an AM radio tuned to static will actually crackle in response to your tapping. If you know Morse code, you’d technically be able to communicate simply with that.

old radioBut let’s dig a little deeper into the technology behind all this: back when the radio was being developed for the first time, transmitters called spark coils were used to create a continuous stream of sparks at around 20,000 volts. The high voltage created large sparks that could be picked up by radios from far away; this is now illegal because it will spam the entire radio, but back in the old days it was fine because barely anyone listened to the radio or knew what it was anyway.

So transmitting with static isn’t so hard, but how do you transfer more elaborate noises, like a voice? Once radio started picking up, it became necessary to use continuous sine waves in order to transfer information in its audio, video or data form. Sine waves allow for a variety of frequencies that makes it possible for many different people to broadcast on the radio simultaneously, whether its a radio station or a police radio.

Every radio has two basic parts: the transmitter and the receiver. The transmitter encodes a message (like a voice, a picture, data, or whatever) and encodes it onto a sine wave that is when transmitted with radio waves. The receiver receives those radio waves and then decodes the message. Both the transmitter and receiver use antennas in order to radiate and capture the radio signal.

smartphoneAn excellent and extremely simple example of this is a baby monitor. A transmitter sits in the baby’s room and acts as a mini radio station. The parents carry the receiver around with them so that they can hear the baby.

A cellphone is a much more complicated example of a radio; more complicated enough that people almost never think of their smartphones as radios. However, any phone does contain both a transmitter and a receiver, and the phone can sue both of them simultaneously and under hundreds of different frequencies. It can even automatically switch between frequencies if necessary.