The remarkable advancement of science and technology today provides us with various forms of entertainment no matter where or when you are. We can listen to music on an iPod, watch movies online on a tablet, or play games on our phones. However, there is a form of entertainment with a long history of development that still exists today as a spiritual sustenance for many people around the world. This is the radio.
The radio (also known as a radio receiver, radio set) is a very familiar device for Vietnamese people, from children listening to the “goodnight baby” program to adults tuning in to news broadcasts or “late-night storytelling.” Radios also serve professional purposes, such as for drivers who rely on “traffic radio” channels.
Radio Waves and Radios
Radio waves, or electromagnetic waves, are a form of electromagnetic radiation with longer wavelengths than infrared light, with frequencies ranging from 3 kHz to 300 GHz. Radio waves travel at the speed of light and naturally occur from phenomena such as lightning.
The term “radio” also refers to the device that receives these waves – an electronic device that captures modulated sound waves through an antenna, amplifies them, restores the original sound form, and plays it through speakers for the audience. The radio was developed based on the interrelated advancements in three inventions: radio, telegraphy, and the telephone. Together, these three technologies created a sound reception technology originally known as “wireless telegraphy.”
The working principle of radio waves
In the history of development, many inventors have tried various methods for wireless signal transmission, including electromagnetic induction and ground signal transmission. However, the radio began with the invention of “radio waves” – a type of electromagnetic wave capable of transmitting music, voice, images, and even data through the air from one place to another. Many devices operate using electromagnetic waves, including radios, microwave ovens, mobile phones, remote controls, televisions, and many others. Devices use electromagnetic waves at different frequencies to perform various functions. The frequencies used in radio range from 3 Hz (Extremely Low Frequency – ELF) to 300 GHz (Extremely High Frequency – EHF).
Starting with Electromagnetism…
In the process of researching wireless signal transmission, a series of experiments have been conducted since the early 19th century to study the relationship between electricity and magnetism based on earlier predictions. Notably, in 1800, Alessandro Volta developed methods to generate electric current. Following him, Gian Domenico Romagnosi researched the connection between electric current and magnetism, although his work was not recognized at the time.
It wasn’t until 1829 that Hans Christian Ørsted conducted an experiment demonstrating the magnetic property of electric current, where current flowing through a coil deflected a nearby compass needle. Ørsted’s experiment sparked André-Marie Ampère to develop the theory of electromagnetism, followed by Francesco Zantedeschi’s research into the relationship between light, electricity, and magnetic fields.
Hans Christian Ørsted’s experiment
In 1831, Michael Faraday conducted a series of experiments to demonstrate the existence of electromagnetic induction. He formulated a mathematical model of Faraday’s law, which states that electromagnetic forces can spread outward into the surrounding space of conductors.
Building on previous research, Joseph Henry conducted an experiment proving that magnetic forces could act from a height of 61 meters in 1832. He was also the first to create alternating current oscillating at high frequencies. During his experiment, he observed that alternating current would produce a swinging force with a diminishing frequency until it returned to equilibrium.
…to 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 known as electromagnetic wave theory published in the Royal Society journal titled “the dynamics of the electric field.” He unified important concepts of modern physics: electricity, magnetic fields, and light through his famous four Maxwell’s equations. Although he did not invent radio waves, this theory laid a solid foundation for the emergence of radio waves and modern radio transmitters.
Early Broadcasting Instruments
Mahlon Loomis and the sketch of his 1866 experiment.
In 1866, Mahlon Loomis, an American dentist, conducted an experiment to demonstrate the concept of “wireless telegraphy.” He used two kites flown into the air. On the string of the first kite, he attached an electric meter, while the string of the other kite was connected to an inductor coil. The results showed that the magnetic field from the second coil deflected the electric meter on the first kite’s string. This marked the first successful instance of wireless signal transmission through the air. Twenty years later, the famous German physicist Heinrich Rudolph Hertz further demonstrated that rapidly varying 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 information wirelessly through space. He successfully sent and received the first radio signals in 1895. In the early 20th century, Marconi began to invest in the idea of transmitting signals across the Atlantic Ocean to compete with cable transmission. In 1901, he transmitted the first wireless signal across the ocean from Poldhu, Cornwall, in southwest England to Signal Hill in St. John’s, Newfoundland, now part of Canada. The distance between the two points was approximately 3,500 km. The feedback signal Marconi received was three clicks, corresponding to the letter S in Morse code. In 1909, Marconi and Karl Ferdinand Braun were awarded the Nobel Prize in Physics for their “notable contributions to the development of wireless communication technology.”
Electrical engineer/inventor Guglielmo Marconi (1874-1937) with his first transatlantic wireless communication system in the UK in 1901
In addition to Marconi, his contemporaries Nikola Tesla and Nathan Stufflefield also received patents for wireless transmission devices in the United States.
The Development Phase
Messages transmitted by radio waves are similar to long and short signals (Morse code). In the early days, the signaling device was referred to as “spark-gap machines.” It was developed to guide ships while docking or to maintain communication between vessels. This was a method of transmitting signals between two points, but it was not the type of radio we see today.
Image of Marconi’s first 230kW “spark-gap machines.” The characters imprinted on the machine are W MACKIE & C, 47 1/2 OLD ST, LONDON EC.
The method of wireless signal transmission using radio waves has proven its effectiveness in rescue operations during natural disasters. These wireless signaling devices were installed on several ships. In 1899, the United States Navy established a wireless communication network between lighthouse ships off the coast of Fire Island, New York. Two years later, the U.S. Navy officially adopted this wireless radio communication system in the military, using it alongside visual signaling methods and carrier pigeons.
Radio station in Hawaii, 1901. (Source: radiomarine.org)
In 1901, a radio telegraph service was established among five islands in the Hawaiian archipelago. By 1903, the Marconi station at Wellfleet, Massachusetts, sent a welcoming 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 via wireless telegraphy, and in 1906, the U.S. Weather Bureau adopted this method to improve the speed of weather forecasting communications.
Famous telegram between President Theodore Roosevelt and King Edward VII, 1903. (Source: royal.co.uk)
In 1910, Marconi launched a wireless messaging service between the United States and Europe, and a few months later, a murder suspect fleeing from England was captured at sea due to information transmitted by this service. In 1912, the first trans-Pacific radio telegraph service was established between San Francisco and Hawaii.
Lee De Forest – The Father of Radio
The development of wireless messaging services in other countries progressed slowly due to the high manufacturing costs of early radio transmitters and unstable current in the systems. However, the high-frequency generators of Alexanderson and De Forest’s vacuum triode largely addressed these initial shortcomings.
Lee DeForest and his three-legged triode invention. (Photo taken around 1914 to 1932, source: Wikipedia)
Lee De Forest invented the space telegraph using the triode amplifier and the Audion. In the early 1900s, the development of radio technology reached a new milestone with the discovery of electromagnetic radiation. De Forest was the one who discovered this phenomenon, which allowed the amplification of radio frequency signals transmitted by antennas before being received by a detector. The transmitted signals were stronger than before. De Forest also coined the term “Radio.”
De Forest’s invention was the amplifier and amplitude modulation or AM radio waves, which allowed signals to be broadcast to multiple stations compared to the previous spark-gap transmission method, which only permitted communication between two points. This laid the foundation for modern radio transmission technology, with De Forest being its pioneer.
Military Applications and Era of Control
When the United States entered World War I, all radio stations in the U.S. were controlled by the military to prevent enemy spies from using them to transmit information. The U.S. government also took over control of all patents related to this radio technology.
In 1919, after the government lifted restrictions on these patents, the Radio Corporation of America (RCA) was established to manage the distribution and application of radio-related patents that had been restricted during the war.
The First Broadcast Voice
The transmission of the human voice over radio remains a topic of debate. Some argue that the first recognized voice was “Hello Rainey”, spoken by Nathan B. Stubblefield to his collaborator in Murray, Kentucky, in 1892. Others claim that the first radio voice belonged to Reginald A. Fessenden during a test broadcast in 1906, which was 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 amplitude modulation and depth sounding devices. Fessenden, a chemist who worked for Thomas Edison in the 1880s, later founded his own company and invented a method of amplitude modulation based on the “heterodyne principle”, allowing signals to be transmitted through the air without interference.
The Birth of “Proper” Broadcasting
Photo of radio station NAA in Arlington, 1917. (Source: virhistory)
In 1915, the first voice was transmitted by the naval radio station NAA in Arlington, Virginia, across the continent from New York to San Francisco, crossing the Atlantic Ocean to the Eiffel Tower in Paris. On November 2, 1920, KDKA radio station in Pittsburgh broadcast the results of the Harding-Cox election and began a daily broadcasting program.
In 1927, a wireless information system connecting North America and Europe was established, and three years later, it could also connect to South America. By 1935, the first global calls were made, utilizing a combination of wired and wireless broadcasting systems.
The Birth of FM Waves and Modern Radio
In 1933, Edwin Howard Armstrong invented frequency modulation (FM) radio waves. FM waves have the advantage of reducing interference from other electronic devices and the Earth’s magnetic field. By 1936, all transatlantic telephone communications from the U.S. to England and Paris were using this method. By this time, the wired and wireless communication network could connect the U.S. with nearly 187 other points abroad.
Howard and the first FM radio receiver during his honeymoon with his wife. (Photo taken in 1923, source: world.std)
Since then, radio technology has developed rapidly. In 1947, scientists at Bell Labs in New Jersey invented the transistor. By 1954, the Tokyo Telecommunications Engineering Corporation, the predecessor of Sony, became the first company to produce portable transistor radios.
The first transistor radio from Sony. (Source: xtimeline)
In 1965, the first FM broadcasting antenna system in the world was built on the Empire State Building in New York, allowing private FM radio stations to broadcast from one source to multiple receivers simultaneously. This model of radio broadcasting is widely used around the world to this day.
Details of the first FM broadcasting antenna atop the Empire State Building. (Photo taken around 1965, source: lnl.com)
Conclusion
Thus, from the early research on electromagnetic wave theory to the extremely rudimentary signals such as an “S” signal in Morse code or a simple “hello” transmitted between two points, we have evolved into a multitude of modern radio stations today, offering a rich and diverse array of news, current affairs, and entertainment programs.
Beneath all these successes lies an endless effort by scientists and inventors striving to turn the impossible into possible, transforming wired communication into wireless transmission. This has ushered in convenience and countless applications of wireless signal transmission methods across various fields.
