Electronics Questions: How Radio Works

The radio has been a source of information and entertainment for years - but how does it work?

One of the most popular areas of entertainment today is the radio - whether in your car or at home, the radio station provides an endless source of information, music and communication. But what exactly IS radio and how does it work?

First, unless you happen to be in a radio station, you are in possession of a radio receiver - not a transmitter. Your stereo system at home and/or your portable boombox are receivers taking in the signals sent out from a main source and translating them into sounds and words that you can comprehend and enjoy.

Radio waves are a type of electromagnetic wave, and they travel at the same speed as light, or 186,000 miles a second. That means that when you hear the words or music out of your receiver that it's almost instantaneous from the transmitter to your ears with very little delay, if any. Radio waves aren't blocked by tall trees or buildings and can travel through almost anything as they spread out from the transmitter, much like the ripples that occur when you toss a rock into a pool of water. The radio station or the transmitter tower is the center where the rock falls with the waves rolling away and outward.

But what makes up these radio waves? Well, electrical current - or, to be more precise, the vibration of the electric current.

There are two types of electric current, direct and alternating. Direct is exactly what it sounds like, going outward in one direction. But that doesn't work for radio, strangely enough. Radio requires alternating current, which flows in one direction and then reverses itself, going back and forth quickly. Each circuit from the starting point is called a cycle, and an ordinary light bulb goes through about sixty cycles every second. Compare that with radio, which goes from 550,000 to over a million cycles each and every second. This range of frequency is called the broadcast band. If you regulate the number of cycles you can find a variety of wavelengths to broadcast on, which is why you have so many radio stations available.

The transmitter sends out the signal via an antenna, which you've probably seen many times before. It may be right next to the radio station or not too far away in a field, sending the radio waves out to the world. But how does your radio receive the signal and translate it back into words and music?



Every receiver, be it in your car or home stereo, has an antenna that is set to receive the signal being sent out. Now you might be asking why you don't get a slew of noise out of the receiver with all the different waves that must be flying through the air. The trick lies with the receiver - it's been set to select waves of only one specific frequency and to ignore the rest of them. That's why when you look at an older radio (or one set for more varied use) you see short wave, AM and FM listings. As you switch to each set of frequencies your antenna is adjusting to weed out specific frequencies and to only accept certain ones.

So your antenna is now receiving a signal being sent in alternative current, or AC. It now goes through a detector which changes it from AC to DC, or direct current and then feeds it into a receiver which translates the waves into audible sounds, creating the music or voices that you then hear.

One of the first detectors was a mineral crystal made of lead sulfide tuned to a specific frequency. Soon the popularity of having your own personal radio gave way to an entire generation of crystal radio sets being sold for amateurs to build at home. Of course, if the crystal broke then you were out of luck and had to try and find another. In fact, you can find many starter kits still in stores for the budding electronic fan to begin his or her career with.

As time went on the components inside the basic radio set began to shrink, thanks to advances in technology, from the transistor to the computer chip and the crystal to a vibrating oscillator, both a fraction of the size of the original components. As a result the large bulky sets of your grandfather's age have shrunken down to receivers that you can hold in your hand or clip to your belt as you go out jogging, or wear as a headset while traveling.

In today's advanced world of flat screen televisions and cell phones it can be easy to forget that it wasn't always this way - sometimes the only way to get news from outside your local area was via the radio. Orson Welles proved the power of the radio with his live broadcast of "The War of The Worlds" which caused an uproar, due to so many people believing the events in the radio play were actually happening. We can laugh now, but back then the fat chunky radio set was a mainstay of everyday life and as much a source of communication and news as the internet is today.

But you can still buy radio building sets in your local electronic store and look back at this time with your own crystal set. Why not pick up one the next time you're out and take a step back in time?

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