Our story begins in Britain in 1873. A scientist named James Clerk Maxwell developed a mathematical theory of a type of energy. He called this energy ‘electromagnetic waves’.
According to his theory, this kind of energy could pass unseen through the air. However, James Maxwell was unable to prove his theory. Other scientists were unable to prove it either, until the German scientist Heinrich Hertz conducted an experiment around 1887.
Hertz’s experiment was very simple. He used two pieces of metal placed close together. He used electricity to make a spark jump between them. He also built a simple receiver made of wire that was wound into a loop. Small pieces of metal were placed at the ends of the loop, separated by a tiny amount of space. The receiver was placed several metres from the other device.
Heinrich Hertz thus proved that James Maxwell’s idea was correct. Electromagnetic waves passed through the air from one device to the other.
Later, Hertz demonstrated the experiment to his students in a classroom. One of the students asked what use could be made of this discovery. However, Hertz thought his discovery was useless. He said it was interesting, but had no value.
He was wrong. His experiment marked the beginning of electronic communications as we know them today. In recognition of his work, the unit of frequency of a radio wave — one cycle per second — is named the hertz.
Radio waves became known to scientists as Hertzian waves. However, the experiment was still of no use until Guglielmo Marconi improved the device that created Hertzian waves. He began his experiments in Italy in 1894.
Marconi soon managed to transmit sound across a distance of several kilometres. He tried to interest Italian government officials in his discovery, but they were uninterested.
Marconi travelled to Britain. His invention was well received there. In 1897, he founded the Wireless Telegraph and Signal Company. The company opened the world’s first radio factory in Chelmsford, England, the following year.
People quickly began using equipment made by Marconi’s company to send and receive radio messages across long distances.
Ships at sea needed the device. Before Marconi’s invention, they were unable to communicate until they arrived in port. With radio, however, ships could call for help if they encountered difficulties. They could send and receive information.
All of Marconi’s radios communicated using Morse code. Experts could send and receive thirty or forty words a minute using Morse code. Marconi’s radio greatly increased the speed of communication.
On 24 December 1906, radio operators on ships in the Atlantic Ocean near the American coast began hearing strange sounds. At first, it was violin music. Then, they heard a human voice. The voice said, ‘Have a Merry Christmas.’
That voice belonged to a man named Reginald Fessenden. He had been working on a device that could transmit human speech or music via radio waves. He decided to try it out on 24 December. This was the first time that a human voice had been heard on the radio.
Improvements in radio technology then came more quickly. Large companies became interested. Radio broadcasting equipment and receivers were improved.
Fourteen years after Reginald Fessenden’s voice was heard by radio operators at sea, the first real radio broadcast was transmitted. It came from Pittsburgh, Pennsylvania.
The programme was broadcast on radio station KDKA on the evening of 2 November 1920. The man speaking on the radio was Leo Rosenberg. He announced the early results of the presidential election between James Cox and Warren Harding.
The success of the radio industry was sparked by those first KDKA broadcasts. People began buying radios. Other companies realised that radio could be profitable. Just four years after the first KDKA broadcast, there were six hundred radio stations in the United States. Radio stations also began broadcasting in other countries.
They began selling ‘air time’ to pay their workers and for necessary equipment. They sold a few minutes of airtime to different companies, who used it to advertise their products to the radio station’s listeners. This method of supporting radio, and later television, is still used today.
Radio changed the way people thought and lived. It allowed almost everyone to hear news about important events at the same time. Political candidates could be heard by millions of listeners. The same songs could be heard across the country.
The work of British scientist James Maxwell and German scientist Heinrich Hertz paved the way for modern communications technology. This includes television broadcasts, satellite use, mobile phones, radio-controlled toys, and much more besides.
Now, we will explain electromagnetic waves. We will begin with Heinrich Hertz’s experiment. You can also try this experiment. First, adjust the controls on your radio until no stations are received.
You will now need a standard nine-volt battery and a piece of metal currency. Hold the battery near the radio and tap the top of the battery with the coin. You should hear a clicking noise on the radio.
The coin and battery together form a simple radio transmitter. This radio will not transmit very far. However, if you know Morse code, you can use this device to communicate.
Electromagnetic energy travels in a similar way to an ocean wave, moving up and down repeatedly. It also travels at the speed of light, which is 299,792,458 metres per second.
Scientists have learned how to separate radio waves into different lengths, known as frequencies. This enables many radio stations to broadcast simultaneously without interfering with each other.
You may be hearing our broadcast on shortwave. These are frequencies between three and thirty kilohertz. They are often referred to as megahertz. One megahertz is equivalent to one thousand kilohertz.
Shortwave is ideal for broadcasting over very long distances. Shortwave signals bounce off the ionosphere surrounding the Earth and back to the ground, and then back to the ionosphere again.
The first radio broadcasts used amplitude modulation. Although AM radio can be sent over larger distances, the sound quality is not as good as that of a later kind of radio signal processing called frequency modulation. FM radio stations transmit at frequencies ranging from 88 to 108 megahertz. AM radio operates at frequencies between 535 and 1700 kilohertz.
Radio technology continues to improve. Today, the Voice of America (VOA) broadcasts to satellites in space, which send the signal back to stations on the ground. These stations then transmit programmes with a clear signal.
In the United States, people who want satellite radio programmes can subscribe to Sirius XM. The company provides listeners with programmes about music, news, sports, weather, politics, and much more. Many of these programmes do not include commercial advertising. These satellite radio services can be used in cars, homes or on portable devices. An increasing number of radio stations are also broadcasting using digital radio technology.
The internet has also contributed to the expansion of radio programming. Radio stations around the world can broadcast their programmes online for listeners everywhere to hear. Pandora’s Music Genome Project is a database of song descriptions created by the website Pandora. Pandora’s internet radio service can predict which songs listeners will like based on their previous musical choices. With this and other forms of internet radio, listeners can create their own personalised radio programming.
We think Heinrich Hertz would be very proud of the device he made, which he thought would never be of any use, given all these developments.
