Is a continuum of the electromagnetic waves used for data and voice communication?

By Robert M. Hazen, Ph.D., George Mason University

There are a bunch of common divisions in this electromagnetic spectrum. They are radio waves; microwaves; infrared, or heat radiation; then visible light; then ultraviolet; x-ray; and gamma ray. This list is in the order of increasing energy, also decreasing wavelengths. But one of the most important types of wave which is used widely by humans is radio waves. But what are radio waves, and how are they used?

The Electromagnetic Spectrum

The electromagnetic spectrum is the continuum of all possible wavelengths, or equivalently all possible frequencies of electromagnetic radiation. There are no natural sharp divisions in this spectrum. Every possible wavelength, every possible frequency can be produced. And there’s really no natural divisions, except from the human perspective that we see visible light and we don’t see the others.

But from an intrinsic point of view, these are all the same kind of phenomenon: all electromagnetic radiation, all traveling 186,000 miles per second. Radio waves were the very first of the invisible kinds of electromagnetic radiation to be discovered. They exemplified the behavior of electromagnetic radiation.

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Hertz’s Discovery of Radio Waves

Radio waves were discovered by the German physicist Heinrich Rudolph Hertz, and this was in a series of experiments in the late 1880s.

Hertz read James Maxwell’s papers. He was determined to observe these predicted invisible kinds of radiation. He set up a series of experiments to do just that. And he was able to measure the wavelengths and some of the other characteristics of these invisible waves.

By the way, the unit of frequency is called the hertz. A hertz is one cycle per second, and it’s named in his honor. So when you look at your radio dial, you may see kilohertz or megahertz; that’s named after this great German scientist.

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Marconi and Radio Communication

Shortly after Hertz’s research, the practical use of communication by radio was demonstrated by the Italian inventor Guglielmo Marconi. He generated radio waves with a primitive spark device—just making electric sparks—and those created radio waves. And then he used a telegraph to produce short bursts like this.

Much of his success was because he designed and improved  antennas. He was the first one, for example, to take an antenna, put it in a vertical configuration, and ground it so that you had much better reception characteristics. Gradually, he was able to increase the transmission and reception of these radio waves from a mile to ten miles, eventually to 100 miles in the year 1896.

And these were just short bursts of radio pulses, like Morse code. Marconi established the first transatlantic wireless communication in 1908, and he won the Nobel Prize for physics in 1909.

Radio Waves are on the Spectrum

Radio waves include electromagnetic radiation with wavelengths between about a foot up to several miles long, the lowest energy part of electromagnetic spectrum, the longest wavelengths. The frequency of these waves is measured in thousands or millions of cycles per second, that’s kilohertz or megahertz.

Radio waves, like all the electromagnetic waves, are produced when charged particles move back and forth and oscillating. The tall antennas that you see near many radio stations, they are metal structures in which large numbers of electrons actually are oscillating back and forth, producing the strong radio signals that you detect.

Radio waves are ideal for communication because they travel through the atmosphere. They travel through building materials. The shorter wavelength radios, such as what we call FM broadcast waves, are not easily scattered. They require some sort of line of sight to the radio tower, so normally you can’t get an FM radio station more than about 40 or 50 miles from its source.

Amplitude and Frequency Modulation

But under the right conditions, the longer wavelengths, the AM radio broadcasts, actually can curve, bounce off the atmosphere, scatter, and therefore, travel for many hundreds of miles, even beyond the horizon.

Information is commonly conveyed with a radio signal in two contrasting ways. You can change the amplitude of the wave, where you’re changing the intensity of the wave. But you could also use frequency modulation, or FM broadcast, and that’s nothing more than changing the wavelength of the wave slightly. That’s analogous to an FM or frequency modulated broadcast.

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Radio Band Divisions

Because radio waves radiate out in so many different directions and over such great distances, society needs to regulate who uses which wavelength, or which band of radio, as it were.

That’s why we have the International Telecommunications Union, that’s an agency of the United Nations; and also in the United States, the Federal Communication Commission, that’s the FCC. These control what is called electromagnetic real estate because each wavelength is a kind of valuable commodity over which you can convey information.

Specific radio bands are allocated to, for example, amateur radio operators, for police, for emergency vehicles, for navigation, for space communication—very important to have  a separate band for that—and so forth.

In addition, there are a few specific wavelengths that have been set aside as standard frequencies, and they broadcast on that frequency all the time. And you can use your radio receivers to pick up those specific frequencies and make sure that your equipment is working properly.

Radio Astronomy

Radio astronomers use large dish-like antennas to detect radio waves that are coming from distant objects: stars and galaxies that are far, far away.  These stars and galaxies have swirling  clouds of charged particles and so many objects in space emit radio waves because they are accelerating charged particles.

Those waves travel 186,000 miles per second through space, sometimes for hundreds of millions of years and they’re picked up by radio telescopes. You can also use radio waves as a way to possibly detect the existence of intelligent life elsewhere in the universe because if you wanted to communicate from one planet, from one star to another, that’s the way you’d do it.

Radio waves are thus one of the most important form of electromagnetic radiation which is an integral part of human technology, especially communication.

Common Questions about Radio Waves

Q: Who discovered radio waves?

Radio waves were discovered by the German physicist Heinrich Rudolph Hertz, and this was in a series of experiments in the late 1880s.

Q: How was radio communication practically demonstrated?

The practical use of communication by radio was demonstrated by the Italian inventor Guglielmo Marconi. He generated radio waves with a primitive spark device—just making electric sparks—and those created radio waves. And then he used a telegraph to produce short bursts like this.

Q: Why are radio waves ideal for communication?

Radio waves are ideal for communication because they travel through the atmosphere. They travel through building materials. The shorter wavelength radios, such as what we call FM broadcast waves, are not easily scattered.

Q: How are radio bands allocated?

Specific radio bands are allocated to, for example, amateur radio operators, for police, for emergency vehicles, for navigation, for space communication—very important to have a separate band for that—and so forth. In addition, there are a few specific wavelengths that have been set aside as standard frequencies, and they broadcast on that frequency all the time.

Keep ReadingFrom Radio to Television: The History of Electronic CommunicationWho Invented Radio Astronomy? A History of the Radio TelescopeRadio Hiss, Einstein’s Theory of Relativity, and the Universe

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