“The golden age “Radio” supposedly ended in the 1950s with the advent of television. But guess what? Television programs were broadcast using radio signals. But today? Radio is everywhere. You have a radio in your car, but maybe you prefer to stream music on your phone. Well, how does music reach you? Yes, via radio waves from cell towers. Your GPS works on the radio too. Just like your home Wi-Fi and Bluetooth.
Radio waves are a type of electromagnetic radiation, just like visible light. However, they are on the lower end of the spectrum, which makes them harmless to humans because low frequency means low energy. (High-frequency and high-energy radiation such as X-rays and gamma rays are a different story.) This is one of the reasons why radio waves are ideal for wireless communication. They can also travel long distances and pass through obstacles such as walls.
Radio is therefore as relevant as ever. But did you know that you can easily build your own radio transmitter and receiver at home using simple materials? I’ll show you how. It’s a cool project and a good excuse to explore some cool physics.
What is an electromagnetic wave?
What is a wave anyway? Imagine you have a long string, one end of which is tied to a door handle. You stand on the other side of the room, holding the other end. If you shake your hand up and down, you will create a disturbance on the string that will move along the string. This is wave. Basically, waves transfer energy without transferring matter.
What if you take away the string? In this case, you will look like a sad man shaking hands with an imaginary friend. Without string there is no wave. Waves need something to “ripple” to – they need a medium. There are no ocean waves without water. Sound waves cannot exist in space because there is no air to wave through.
But what if, instead of a string, you shook an electric charge (like an electron) up and down? Electric charges create electric fields, so that’s it moving the charge will create an oscillating electric field that will create an electric wave. This is where it gets weird: It turns out that changing the electric field also causes a change magnetic field. Conversely, a changing magnetic field produces a changing electric field. We know this from Maxwell’s equations.
This means that we are dealing with electric and magnetic oscillations that move together, each of which is the center of the other. This connection is called electromagnetic radiation, also known as “delicate”. Yes, radio waves are just light and light Power they spread in empty space – basically at the speed of light.
Piezoelectric radio station
OK, let’s make a radio wave! All you need for the transmitter is a grill lighter – you know, the one with the long tube. When you hold the trigger, gas escapes from the end of the tube and ignites with a small spark. Here’s one I cut in half:
Photo: Rhett Allain