Description:
Radio is a crucial element in the world of electronics. It"s the fundamental technology behind TV, cordless phones, cell phones and microwave ovens, for a start. Find out about radio waves.

Radio is a crucial element in the world of electronics. It"s the fundamental technology behind TV, cordless phones, cell phones and microwave ovens, for a start. Find out about radio waves.

"Radio waves" transmit music, conversations, pictures and data invisibly through the air, often over millions of miles -- it happens every day in thousands of different ways! Even though radio waves are invisible and completely undetectable to humans, they have totally changed society. Whether we are talking about a cell phone, a baby monitor, a cordless phone or any one of the thousands of other wireless technologies, all of them use radio waves to communicate.

Here are just a few of the everyday technologies that depend on radio waves:

AM and FM radio broadcasts
Cordless phones
Garage door openers
Wireless networks
Radio-controlled toys
Television broadcasts
Cell phones
GPS receivers
Ham radios
Satellite communications
Police radios
Wireless clocks

The list goes on and on... Even things like radar and microwave ovens depend on radio waves. Things like communication and navigation satellites would be impossible without radio waves, as would modern aviation -- an airplane depends on a dozen different radio systems. The current trend toward wireless Internet access uses radio as well, and that means a lot more convenience in the future!

The funny thing is that, at its core, radio is an incredibly simple technology. With just a couple of electronic components that cost at most a dollar or two, you can build simple radio transmitters and receivers. The story of how something so simple has become a bedrock technology of the modern world is fascinating!

In this article, we will explore the technology of radio so that you can completely understand how invisible radio waves make so many things possible!

The Simplest Radio
Radio can be incredibly simple, and around the turn of the century this simplicity made early experimentation possible for just about anyone. How simple can it get? Here"s an example:
Take a fresh 9-volt battery and a coin.

Find an AM radio and tune it to an area of the dial where you hear static.
Now hold the battery near the antenna and quickly tap the two terminals of the battery with the coin (so that you connect them together for an instant).
You will hear a crackle in the radio that is caused by the connection and disconnection of the coin.

By tapping the terminals of a 9-volt battery with a coin, you can create radio waves that an AM radio can receive!

Your battery/coin combination is a radio transmitter! It"s not transmitting anything useful (just static), and it will not transmit very far (just a few inches, because it"s not optimized for distance). But if you use the static to tap out Morse code, you can actually communicate over several inches with this crude device!

A (Slightly) More Elaborate Radio
If you want to get a little more elaborate, use a metal file and two pieces of wire. Connect the handle of the file to one terminal of your 9-volt battery. Connect the other piece of wire to the other terminal, and run the free end of the wire up and down the file. If you do this in the dark, you will be able to see very small 9-volt sparks running along the file as the tip of the wire connects and disconnects with the file"s ridges. Hold the file near an AM radio and you will hear a lot of static.

In the early days of radio, the transmitters were called spark coils, and they created a continuous stream of sparks at much higher voltages (e.g. 20,000 volts). The high voltage created big fat sparks like you see in a spark plug, and they could transmit farther. Today, a transmitter like that is illegal because it spams the entire radio spectrum, but in the early days it worked fine and was very common because there were not many people using radio waves.