Radio, also known as radio or broadcasting, is a technology for transmitting information using modulated electromagnetic waves with frequencies lower than the frequency of light, radio waves.
History of radio and broadcasting technology
Radio and electromagnetic wave projection diagram
Radio waves or radio waves are a form of electromagnetic radiation with a spectrum longer than infrared light, frequencies from 3 kHz to 300 GHz. Radio waves travel at the speed of light and in nature, they appear from the phenomenon of thunder.
The word radio is also used to refer to a radio receiver – an electronic device used to receive modulated sound waves through an antenna to amplify, restore the original sound form, and play it through the speaker.
Starting with electromagnetism …
In the process of researching this field of wireless signal transmission, a series of experiments were conducted since the beginning of the 19th century to study the relationship between electricity and magnetism based on previous predictions. Typically, in 1800, Alessandro Volta developed methods to generate electric current. This was followed by Gian Domenico Romagnosi with his research on the relationship between electric current and magnetism, but his research was not recognized.
It was not until 1829 that Hans Christian Ørsted conducted an experiment to demonstrate the magnetic properties of electric current, that is, the current flowing in a coil deflected the direction of a nearby compass needle. It was Ørsted’s experiment that inspired André-Marie Ampère to develop the theory of electromagnetism and then Francesco Zantedeschi with his research on the relationship between light, electricity and magnetism.
Experiments by Hans Christian Ørsted
In 1831, Michael Faraday conducted a series of experiments to prove the existence of the phenomenon of electromagnetic induction. This relationship was built into a mathematical model of Faraday’s law. Accordingly, the electromagnetic force can spread to the space around the conductors.
Based on previous studies, Joseph Henry conducted an experiment to prove that the magnetic force can act from a height of 61 m in 1832. He was also the first person to create an alternating current that oscillates at a high frequency. In the experiment, he realized that the alternating current would create an oscillating force with a decreasing frequency until it returned to a state of equilibrium.
… to the electromagnetic wave theory:
James Clerk Maxwell (1831-1879) father of electromagnetic wave theory.
From 1861 to 1865, based on the research of Faraday and other scientists, James Clerk Maxwell developed a theory called the electromagnetic wave theory published in the Royal Scientific Journal with the title “Dynamic theory of electric fields”. He was the one who unified the important concepts of modern physics: electricity, magnetism and light with the famous 4 Maxwell equations. Although he was not the inventor of radio waves, this theory laid a solid foundation for the birth of radio waves as well as today’s radio transmitters.
“Early” radio equipment:
Mahlon Loomis and his 1866 experimental sketch.
In 1866, Mahlon Loomis – an American dentist conducted an experiment to prove the concept of “wireless telegraphy.” In it, he used 2 kites flying in the air. On the first kite string, he mounted an electric meter while on the other kite string, he mounted an electromagnetic coil. The results of the experiment showed that in the air, the magnetic field from the second coil deflected the electric meter on the first kite string. This marked the first successful case of wireless transmission in the air. And 20 years later, the famous German physicist Heinrich Rudolph Hertz once again demonstrated that rapidly changing electric currents could be transmitted through space as radio waves, similar to light and heat.
The first radio signals:
Guglielmo Marconi, an Italian inventor, demonstrated the feasibility of transmitting radio information in space. He successfully transmitted and received the initial radio signals in 1895. And in the early years of the 20th century, Marconi began investing in an idea to transmit signals across the Atlantic to compete with the cable transmission. In 1901, he transmitted the first wireless signal across the ocean from Poldhu, Cornwall – a county in the southwest of the UK – to Signal Hill in St John’s, Newfoundland – now a Canadian archipelago. The distance between the two points was about 3,500 km. The response Marconi received was a three-tone click, representing the letter S in Morse code. In 1909, Marconi and Karl Fedinand Braun received the Nobel Prize in Physics for “remarkable contributions to the development of wireless communication.”
Electrical engineer/inventor Guglielmo Marconi (1874-1937) with his first transatlantic wireless communication system in England in 1901.
In addition to Marconi, two of his contemporaries, Nikola Tesla and Nathan Stufflefield, also received patents for radio transmitters in the United States.
The development stage:
The messages transmitted by radio waves were similar to long-short signals (Morse code). In the early days, the transmitters were called “spark-gap machines”. They were developed to guide ships when they were approaching ports or to keep in touch with each other. It was a way to transmit signals between two points, but it was not the radio that we see today.
Image of Marconi’s first 230kW “spark-gap machines”. The letters cast on the body read W MACKIE & C, 47 1/2 OLD ST, LONDON EC.
The method of transmitting wireless signals using radio waves has proven its effectiveness in rescue operations when natural disasters occur. These wireless signal transmission devices were installed on a number of ships. In 1899, the United States Navy established a wireless communication network between lighthouses off Fire Island, New York. Two years later, the US Navy officially adopted this radio wireless communication system for military use, using it in parallel with visual transmission and pigeon communication.
Image of a broadcasting station in Hawaii in 1901. (Source: radiomarine.org)
In 1901, a radio telegraph service was set up to connect the five Hawaiian Islands. In 1903, the Marconi station in Wellfleet, Massachusetts, sent a greeting message from President Theodore Roosevelt to King Edward VII of England. In 1905, reports of the naval battle at Port Arthur during the Russo-Japanese War were transmitted by wireless telegraphy, and in 1906, the US Weather Bureau adopted this method To enhance the transmission speed of weather forecast information.
The content of the famous telegram between President Theodore Roosevelt and King Edward VII in 1903.
(Source: royal.co.uk)
In 1910, Marconi opened a wireless service between the United States and Europe and a few months later, an escaped murderer from England was caught at sea using the information transmitted by this service. In 1912, the first radio telegraph service across the Pacific was set up to connect San Francisco and Hawaii.
Lee De Forest – Father of Radio:
Radio telegraphy in other countries developed rather slowly because the first generations of transmitters were quite expensive to manufacture, the current in the system and the discharge current between the electrodes were not stable. However, Alexanderson’s high-frequency generator and De Forest’s vacuum Triode tube later overcame most of these initial shortcomings.
Lee DeForest and his invention of the three-legged triot lamp. (Photo taken between 1914 and 1932, source Wikipedia)
Lee De Forest invented space telegraphy using a Triode amplifier and a 3-pole tube (Audion). In the 1900s, the development of radio technology reached a new milestone with the discovery of electromagnetic radiation. Lee De Forest was the one who discovered this phenomenon. Accordingly, electromagnetic radiation can amplify radio frequency signals transmitted by antennas before being received by a receiver. The transmitted signal has a stronger intensity than before. De Forest was also the first person to name this amplification system “Radio”.
De Forest’s AM Radio Broadcasting System. (photo taken circa 1916, source Wikipedia)
De Forest’s invention was the Amplitude-Modulated or AM radio wave that allowed signals to be transmitted to many different stations compared to the previous spark-gap transmission method that only allowed transmission between 2 points. This is the premise of modern radio transmission technology, of which De Forest is the father.
Military Applications and Controlled Periods:
When the United States entered World War I, all radio stations in the United States were controlled by the military to prevent enemy spies from using them to transmit information. The U.S. government also took control of all patents related to this radio technology.
In 1919, after the government abolished these patent restrictions, the Radio Corporation of America (RCA) was formed to control the distribution and application of the radio-related patents that had been restricted during the war.
The First Radio Voice:
The human voice being transmitted over the radio remains a matter of controversy. One argument is that the first recognized voice was “Hello Rainey” spoken by Nathan B. Stubblefield to his collaborator in Murray, Kentucky in 1892. Another argument is that the first radio voice was Reginald A. Fessenden’s experimental talk show in 1906, heard by a radio device on ships hundreds of miles away.
Reginald A. Fessenden and his radio system.
Canadian inventor Reginald A. Fessenden is also known for his invention of radio modulation and the depth finder. Fessenden was a chemist who worked for Thomas Edison in the 1880s. He later founded his own company and invented a method of radio modulation based on the “heterodyne principle” that allowed signals to be transmitted over the air without interference.
“Proper” radio broadcasts are born:
Photo of the NAA radio station in Arlington in 1917. (Source: virhistory)
In 1915, the first voice was transmitted transcontinentally by the NAA Naval Radio Station in Arlington, Virginia, from New York to San Francisco, across the Atlantic to the Eiffel Tower in Paris. On November 2, 1920, KDKA – Pittsburgh radio broadcast the Harding-Cox election results and began a daily radio program.
In 1927, the radio communication system connecting North America and Europe was established, and 3 years later, it was possible to connect South America. Until 1935, the first calls were made worldwide, using a combination of both wired and wireless broadcasting systems.
The birth of FM waves and today’s radio:
In 1933, Edwin Howard Armstrong invented frequency-modulated radio waves, also known as FM radio waves. FM waves have the advantage of limiting interference from other electronic devices and the Earth’s magnetic field. By 1936, all US transatlantic telephone communications transmitted to England and Paris used this method. Up to that time, both wired and wireless communication networks could connect the US with nearly 187 other points abroad.
Photo of Howard and the first FM radio on his honeymoon with his wife. (photo taken in 1923, source: world.std)
Since then, radio technology has always developed extremely rapidly. In 1947, scientists at Bell Labs in New Jersey, USA invented the transistor. And in 1954, Tokyo Telecommunications Engineering Corp – the predecessor of Sony – was the first company to produce portable transistor radios.
Sony’s first transistor radio (Source: xtimeline)
In 1965, the world’s first FM broadcasting antenna system was built on the Empire State Building in New York, allowing private FM radio stations to broadcast from one source to many different receivers at the same time. This is also the radio model that is widely applied around the world to this day.
Detail of the first FM broadcasting antenna on top of the Empire State Building (Photo taken circa 1965, source: lnl.com)
Thus, from the first studies on electromagnetic wave theory, to very primitive signals such as a character S in Morse code or a “hello” transmitted between two points, we have a series of modern radio stations today with extremely rich and diverse news, current affairs, and entertainment programs.
Underneath all those successes is an endless effort of scientists and inventors to turn the impossible into possible, to turn wired communication into wireless. Thereby, creating convenience and a series of applications of wireless signal transmission methods for many different fields.
