HOW RADIOS WORK
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How do radios work?

When one thinks of how radio works, they most often first think that it begins with radio waves. While this is certainly true, it’s amazing how many daily uses that are derived from radio waves. Besides just the radio that you tune to a station you want to listen to, many other devices depend on radio waves to operate including: cordless phones, garage door openers, wireless networks, GPS receivers, satellite communications, cell phones, and many more. These radio waves send out music, conversations, pictures, video, and other types of information through the air. The interesting concept of the radio is that as much as it is responsible for, it’s a very basic device.

To understand just how simple a radio can be, get a nine-volt battery and a coin and sit close to an AM radio. Turn the dial until you can hear nothing but static. Hold the battery up to the radio’s antenna and click the coin on the terminals of the battery. The instant the coin hits the terminals, the radio will emit a crackle noise. The same effect will occur the instant the coin is moved away from the battery terminals. The change of electrons when the coin touches causes the battery to transmit a signal and therefore turning the battery into a radio transmitter! Although it will only work if held only a few inches away from each other and nothing is being sent except for static, this method could be used for tapping out Morse code.

Another important element to understand when considering how radio works is sine waves. These waves are able to differentiate which radio waves are going where. Because there are so many devices that use radio waves, there are countless waves constantly being transmitted around you. Sine waves help them not to collide and get the information to wherever it is going. For each different radio signal, there is a different sine wave frequency. The radio itself has two parts: a transmitter and a receiver. The transmitter will pick up whatever it’s supposed to be sending and will turn it into a sine wave. After converting it, it will send it out via a radio wave. The transmitter, the radio element on the other end, will then read this radio wave and decode the sine wave, turning the information into something useful. The transmitter and the receiver speak to each other and send and receive the different waves and signals through antenna.

To see a real example of how radio waves work, upgrade the nine-volt battery radio in the earlier example. Trade in the coin for a piece of wire. Place one end of the wire onto one of the battery terminals and then place the other end onto the other terminal. Electrons will pass through the wire, making enough energy to move a compass. If you were to take a second piece of wire and lay it beside the first wire, but not allowing the two to touch, and then attaching a voltmeter to the second wire, every time you moved or replaced the first wire onto the battery, you would be able to see a small electric current running through the second piece of wire. This will not happen however, unless there is a change in the flow of electrons. The first wire needs to continuously be taken off the battery and placed back on for the current to be visible.

Transmitting information isn’t entirely the simple end of it however. When a sine wave is being transmitted using an antenna, this creates a radio station. However, those sine waves don’t contain any actual information. The wave needs to be encoded to be able to read it. To encode it, you need to modulate it, which there are three basic ways of doing. Pulse Modulation, which is the most basic of ways to modulate sine waves, is simply switching the sine wave off and on. This form of modulating isn’t used very often however it can be used in Morse code. Amplitude Modulation is another form of modulating that is used more often. It’s actually used by television signals and AM radio stations. In this type of modulating, the sine wave will experience changes in its amplitude. This is how a person’s voice is carried through a sine wave after the amplitude has been modified. Frequency Modulation, such as FM radio, is the best form of modulating because there is almost no static involved. In this form the sine wave is only changed very slightly, depending on what the information signal relays. Once any one method of modulation has been completed, the information can then be transmitted.

When referring to AM radio, a very basic type, the radio needs an antenna to be able to pick up the sine waves. The antenna for an AM radio is simply a thin pole of metal that will help the sine waves interact with the radio and work to transmit it. A tuner is also needed. Of course, this is the dial that you use to change the radio station. Because the antenna will receive literally thousands of sine waves, the tuners job is to separate them all from each other. The tuner will then use a detector or demodulator to pick out of the sine waves whatever the radio station has sent out. To do this, a diode is needed. These allow electrical currents to run in only one direction. This will then clip off some of the sound. That clipped portion is then amplified and sent to the speakers. You then hear the signal the radio is sending out!

 

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