All About Radio!
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Chances are that radio and television have been the go to activities for many of you during isolation. And let’s not forget video and audio podcasting – like this one. Thank god for that – or should we be thanking Marconi? Well, there were others before Marconi, in fact 80 years of science led to him. So, today we are going to talk about all things radio. Radio waves, radio transmission, even radio astronomy.
We have been using radio commercially since 1900 but how we got there goes back a bit. Naturally, we have to start with that most influential of scientists: Michael Faraday, whose experiments established that a changing magnetic field produces an electric current.
This relationship was mathematically modeled by James Clerk Maxwell, a Scottish scientist and another one of the greats. He formulated the classical theory of electromagnetic radiation. Now this theory – for the first time – brought together electricity, magnetism and light. Maxwell proposed in 1865 that electric and magnetic fields travel as waves and that light is part of the same phenomenon. He demonstrated this in his famous equations of electromagnetism and this unification led him to predict radio waves.
Maxwell’s idea was that light consisted of electromagnetic waves of short wavelength, but no one had been able to prove this, and nobody had been able to generate or detect electromagnetic waves of other wavelengths either.
Moving forward to 1887 and we meet German physicist Heinrich Rudholph Hertz. He turned Maxwell’s equation of electromagnetic radiation into a reality, when he experimentally generated radio waves in his lab, also demonstrating that they exhibited the same wave properties as light. Hertz conducted a series of experiments between 1886 to 1889 to prove that what Maxwell had predicted was a reality, using the first radio transmitter to produce radio waves (of around 50 Mhz about what is used in modern TVs). Yes, I said megahertz – because the unit of frequency or “cycles per second” are named after Hertz. And he also coined the phrase “radio spectrum”.
Hertz did not realize the importance of his discovery however, saying “It’s of no use whatsoever[…] this is just an experiment that proves Maestro Maxwell was right—we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there.”
Now before Hertz actually proved the existence of radio waves, there was a dentist called Mahlon Loomis who wanted to show that the layers of Earth’s upper atmosphere could be tapped by metallic conductors on hills and mountaintops to provide long-distance wireless telegraph and telephone communication, as well as draw electricity down to the Earth’s surface. While his theory of conductive atmospheric layers is not true, he was successful in demonstrating wireless telegraphy. Loomis was able to make a meter, connected to a kite, cause another one to move. The first known wireless aerial communication had taken place.
As I said before, Hertz did not think that his discovery of radio waves was of any practical application. Even later experimenters of note, such as Oliver Lodge (who identified electromagnetic radiation independent of Hertz) and Jagadish Chandra Bose (who is known as the father of radio science) thought radio communication was impossible. They did succeed in successfully transmitting radio waves at some distance, but they did not see any value in developing a communication system based on them. However, they developed electronic components and methods to improve the transmission and detection of electromagnetic waves. There was also Russian physicist Alexander Popov who conducted experiments developing a radio receiver n 1894-95, for lightening detection. And let’s not forget Nikola Tesla who, in 1898, developed a radio based remote-controlled boat.
But it took Guglielmo Marconi – an Italian inventor and engineer – who had the vision that radio transmission could be possible across vast distances. He became fascinated with Hertz’s “invisible waves” that were generated by electromagnetic interactions. He built his own wave-generating equipment at his family’s estate in Bologna Italy and experimented with sending signals miles away. He was 20.
It was in December 1894, that Marconi demonstrated a radio transmitter and receiver to his mother. This set up, essentially, made a bell ring on the other side of the room by pushing a telegraphic button on a bench. Marconi continued to experiment with different arrangements and shapes of antennae to sending signals farther and farther away. Eventually in 1895, he realized that he could achieve a greater range by raising the height of the antenna and by grounding his transmitter and receiver. This enabled him to transmit signals up to 2 miles and he concluded that a device COULD become capable of spanning greater distances. And this is when he realized that radio transmission could prove both commercially and militarily valuable. Marconi’s experimental apparatus proved to be the first complete, commercially successful radio transmission system.
The Italian government was not interested in his work, so he moved to London in 1896 to try his luck. Some of his early backers included the British Post Office. This helped him to form a wireless telegraph company in 1897 and a radio station in the Isle of Wight, England. He was soon sending signals as far away as 10 miles. In 1899, Marconi sent the first radio signal across the English Channel. And then he equipped two U.S. ships to report to New York newspapers on the progress of the America’s Cup yacht race. Already he was being noticed.
But he made history when he successfully received a message sent from Cornwall in England at St. John’s, Newfoundland on December 12, 1901. It was a faint three-dot signal – the Morse code for the letter S. Marconi continued to conduct tests from the SS Philadelphia, recording signals from up to 2,100 miles or 3,400 km. In 1904, the US Patent Office finally awarded him a patent for the invention of radio and Marconi received a Nobel Prize for his work in 1909, jointly with Karl Ferdinand Braun “in recognition of their contribution to wireless telegraphy”.
Marconi himself admitted that he did not understand how radio transmission worked. The detractors of his projects had declared that radio waves could not follow the curvature of the earth – Marconi believed they did. It was later confirmed that his radio signal first headed to space, was reflected off one of the layers of the atmosphere and then bounced back toward Canada. There was still a lot of discovery to be made during the 20th century and Marconi played a key role in innovations and discoveries for the next three decades. When the Titanic sank in 1912, it used wireless to contact other vessels, enabling RMS Carpathia to pick up 700 survivors. After this, wireless telegraphy became universal in large ships. So, while Marconi did not actually technically INVENT the radio, he was able to build upon the work of many scientists before him. And he had the vision to develop better equipment and innovate new technology.
From then on radio broadcasting became a norm, with the first ever radio broadcast for entertainment and music to the public transmitted by Reginald Aubrey Fassenden on December 24, 1906, from Brant Rock Massachusetts. Fassenden pioneered a complete system of transmission and reception using the amplitude modulation or AM system. In 1922, the British Broadcasting Company (BBC) began its daily transmissions from Marconi house. And the Regency TR-1, was the world’s first commercially produced transistor radio.
So, let’s talk about radio waves, which as Maxwell had predicted are a part of electromagnetic radiation. Radio waves have frequencies as high as 300 gigahertz to as low as 30 hertz. Waves have wavelengths and at 300 GHz their corresponding wavelength is 1 mm, while at 30 hertz it is 10,000 km. A wavelength can be shorter than a grain of rice to longer than the diameter of earth. We use them not only in radio communication and broadcasting but also in radar, navigation, communication satellites, wireless computer networks and a host of other applications.
While Marconi’s radio waves could not do this, long waves (called ground waves) CAN diffract around obstacles like mountains and follow the contour of the earth. Shorter waves can reflect off the ionosphere and return to earth and are called sky waves. Much shorter wavelengths bend or diffract very little and travel on a line of sight, so their propagation distances are limited to the visual horizon.
Did you know that the use of radio waves is strictly regulated by law, coordinated by an international body called the International Telecommunications Union (ITU)? The radio spectrum is divided into a number of radio bands based on frequency and allocated to different uses. Radio waves passing through different environments experience reflection, refraction, polarization, diffraction, and absorption. Different frequencies experience different combinations of these phenomena in the Earth’s atmosphere, making certain radio bands more useful for specific purposes than others. For example, FM and AM are the bands used for broadcasting. And now we have of course moved on to digital broadcasting using digital rather than analogue signals. We use radio waves whenever we use our wireless routers for the internet.
Let’s clear one thing here, radio waves do not have enough energy to separate electrons from atoms or to break chemical bonds so there is limited evidence that they cause DNA damage or are carcinogenic.
Let’s come to radio astronomy, a field that studies celestial objects at radio frequencies. Karl Jansky at Bell Telephone Laboratories detected the very first radio waves from an astronomical object in 1932 when he observed radiation coming from the Milky Way. And now astronomers have identified a number of different sources of radio emissions such as stars, galaxies, quasars, pulsars etc. using radio telescopes.
But one of the most important discoveries of radio astronomy was that of the cosmic microwave background radiation, which is regarded as evidence for the Big Bang theory.
We use radio waves everywhere! Even I am using them in this broadcast and so are you.
Title music: Hovering Thoughts by Spence (YouTube Music Archive)
All images: Public Domain
Featured Image: Pixabay