Surfing the Waves
There is no escaping it, all around us all sorts of equipment are emitting radio waves. Think about it… Cell Phones, GPS Receivers, police radios, TV broadcasts, and so on and so forth.
Although radio waves are invisible, they have completely changed our lives. If you are not convinced that these waves (surf’s up!) exist try the following.
There is a very easy experiment you can do yourself to send a signal via radio waves.
Take a 9-volt battery and a coin. Find an AM radio and tune it to a frequency where you can only hear static. Hold the battery close to the radio’s antenna and quickly tap the coin to the battery’s contacts (let them only touch for a moment).
The moment the coin (dis)connects the battery you’ll hear a crack on the radio. This is cause by the signal that has been sent via the battery/coin combo. It’s not very useful and frankly it won’t go any far, but it’s there.
As you noticed, it’s fairly simple to transmit with static. But you can imagine this forms a problem. There are so many devices out there broadcasting signals that at some point they will interfere. That’s why all radio transmitters today are using something that is called a continuous sine wave. Each radio frequency is using a different one and that is how they are kept apart.
Any radio setup works like getting married. You can’t do it alone. So any setup has 2 parts. A transmitter and a receiver. You probably already figured out that the transmitter sends a message (which really could be anything, a voice, pictures, whatever) by encoding it into a sine wave which is transmitted by radio waves.
The receiver, of course, receives the message and decodes it. Both devices use an antenna to send or receive the signal.
Radio waves where first “predicted” by a man called James Clerk Maxwell. He did some serious mathematical work in 1867. This man noticed the wavelike properties of light and the similarities in electrical and magnetic observations. After this observation he proposed a set of equations that described light waves and radio waves as actual waves of electromagnetism that travel in space.
Heinrich Hertz (ring a bell?) proved the reality of Maxwell’s electromagnetic waves by generating radio waves in his laboratory (I’m telling you he was 1 lab accident away from being an super villain).
From that day forward new inventions were created and it brought us were we are now.