Radio, also known as radio or radio, is a technique for transferring information using a way of modifying electromagnetic waves with lower frequencies than light, radio waves.
Radio and electromagnetic projection charts
Radio waves or radio waves are a form of electromagnetic radiation that has a longer spectrum than infrared light, the frequency from 3 kHz to 300 GHz. Radio waves transmit at the speed of light and in nature, it comes from lightning.
The radio is also used to refer to a radio receiver - an electronic device used to receive sound waves that have been modulated via antennas to amplify, restore the original sound, and emit in the speaker.
During the study of this field of wireless signal transmission, a series of experiments have been 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 create electricity. Next is Gian Domenico Romagnosi with research on the relationship between electric and magnetic currents but his research has not been recognized.
It was not until 1829 that Hans Christian nghiệmrsted gave an experiment to prove the magnetic property of an electric current, which is the current flowing in a coil that deflects the compass needle near. It was Ørsted's own experiment that initiated André-Marie Ampère to develop the theory of electromagnetism and then Francesco Zantedeschi with the study of the connection between light, electricity and magnetism.
Hans Christian stedrsted's experiment
In 1831, Michael Faraday conducted a series of experiments to prove the existence of electromagnetic induction . This relationship was built by him into a mathematical model of Faraday's law. Accordingly, the electromagnetic force can spread to the space around the wires.
Based on previous studies, Joseph Henry performed an experiment that demonstrated magnetic force that could impact from a height of 61 m in 1832. He was also the first person to generate alternating current with high frequency . In the experiment, he realized that alternating current would produce an oscillating force with a reduced number of layers until it returned to equilibrium.
. to electromagnetic waves theory:
James Clerk Maxwell (1831-1879) the father of the theory of electromagnetic waves.
From 1861 to 1865, based on studies by Faraday and other scientists, James Clerk Maxwell developed a theory called the electromagnetic wave published in royal science magazine with the title " dynamics theory of electric fields ". He is the one who unifies the important concepts of modern physics: electricity, magnetism and light with four famous Maxwell equations. Although he was not the inventor of radio waves, it was this theory that laid a solid foundation for the birth of radio waves and radio today.
"Early childhood" radio tool:
Mahlon Loomis and experimental sketchbook in 1866.
In 1866, Mahlon Loomis - an American dentist conducted an experiment to prove the concept of "wireless telegraphy ." In it, he used 2 flying kites in the air. On the first kite string, he installed an electric meter while the other kite string was fitted with an electromagnetic coil. The results from the experiment showed that in the air, the magnetic field from the second coil twisted the electric meter on the 1st kite wire. This is the case that marks the first success of the signal transmission. wire in the air. And 20 years later, the famous German physicist Heinrich Rudolph Hertz once again demonstrated the rapid variability of electric current that could be transmitted in space as radio waves similar to light and heat.
First radio signals:
Guglielmo Marconi , an Italian inventor demonstrated the feasibility of transmitting radio information in space. He successfully sent and received the first radio signals in 1895. And in the early years of the 20th century, Marconi began investing in an idea of transatlantic signaling to compete with the type of transmission. Branded by cable. In 1901, he transmitted the first wireless signal through the ocean from Poldhu, Cornwall - a county in southwestern England to Signal Hill at St John's, Newfoundladn - now a Canadian-owned archipelago. . The distance between the two points is about 3500 km. The feedback signal that Marconi receives is 3 click sounds - corresponding to the letter S according to Morse code. In 1909, Marconi and Karl Fedinand Braun both received the Nobel Prize in physics for their "contribution to the recognition of the development of wireless communications technology."
Electrical engineer / house invented Guglielmo Marconi (1874-1937) and his first transatlantic wireless communication system in the United Kingdom in 1901.
In addition to Marconi's case, his contemporaries Nikola Tesla and Nathan Stufflefield also received a patent for radio transmitters in the United States.
Complete development stage:
The messages transmitted by radio waves are similar to long-short signals (Morse code). In the beginning, the signal generator was called "spark-gap machines" . It was developed to guide ships while docking or to keep in touch between ships. It is a way of signaling between two points but that is not the radio that we see today.
Marconi's first 230kW "spark-gap machines" transmitter.The characters cast on the camera body are W MACKIE & C, 47 1/2 OLD ST, LONDON EC.
The method of transmitting wireless signals by radio waves has proved its effectiveness in rescuing and rescuing people when disasters occur. These wireless signal transmitters are installed on a number of ships. In 1899, the US Navy established a wireless communication network between lighthouse ships off the island of Fire in New York state. Two years later, the US Navy officially adopted this radio-based wireless communication system in the military, used in parallel with visual communication methods and pigeon communication.
Image of broadcasting station in Hawaii in 1901. (Source: radiomarine.org)
In 1901, the radio telegraph service was established between five islands of the Hawaiian Islands. In 1903, the Marconi station located in Wellfleet, Massachusetts sent a welcome message from President Theodore Roosevelt to King Edward VII of England. In 1905, reports of naval battles at Port Arthur during the Russo-Japanese War were transmitted by wireless telegraphy, and in 1906, the US weather forecast department applied this method to improve the speed of weather forecast information transmission.
The famous telegram content between President Theodore Roosevelt and King King Edward VII in 1903.
In 1910, Marconi opened a wireless communication service between the United States and Europe and a few months later, a murderer escaped from England on the sea with information transmitted by the service. this. In 1912, the first trans-Pacific telegraph service was established between San Francisco and Hawaii.
Lee De Forest - Father of radio:
Radio communication services in other countries developed quite slowly due to the initial generation of transmitters with high manufacturing costs, the current in the system and the flow of electricity between the electrodes have not been stabilized. . However, then Alexanderson's high-frequency generator and De Forest's vacuum Triode tube overcame most of these early defects.
Lee DeForest and his 3-foot triot light emitted.
(Photo taken between 1914 and 1932, Wikipedia source)
Lee De Forest invented telegraphy in space using Triode amplifiers and 3-pole lamps (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 the radio frequency signal transmitted by the antenna before being retrieved by a receiver detector. The broadcast signal is more intense than before. De Forest was also the first person to name this amplifier system " Radio".
De Forest's Radio AM broadcast system.(photo taken around 1916, Wikipedia source)
De Forest's invention is the Amplitude-Modulated or AM radio amplifier and modulator that allows the signal to be transmitted to different stations compared to the previous spark-gap transmission method that only allows transmission believe between 2 points. This is the premise of modern radio communication technology that De Forest is the father.
Military applications and periods of control:
When the United States participated in World War I, all radio stations in the United States were controlled by the military to prevent the possibility of enemy spies using it to transmit information. The US government also took over control of all patents related to this wireless technology.
In 1919, after the government abolished the policy of restricting these patents, the US Broadcasting Corporation (RCA) was established to control the distribution and application of radio-related patents. was restricted in the war.
First radio voice:
Human voices transmitted through radio are still a controversial issue. It is argued that Nathan B. Stubblefied's first voice was recognized as " Hello Rainey " to his collaborator in Muray, Kentucky in 1892. Another argument argued that the first voice was broadcast. belong to the chat program of Reginald A. Fessenden in 1906 and heard by a radio device on ships hundreds of miles away.
Reginald A. Fessenden and his radio system.
The Canadian inventor, Reginald A. Fessenden, is also known for his radio wave inventions and depth detectors. Fessenden was a chemist who worked for Thomas Edison in the 1880s. After that, he founded his own company and invented radio wave modulation based on " heterodyne principle". Allows signal transmission in the air without interference.
"True" radio programs are born:
Photo of NAA radio station in Arlington in 1917. (Source: virhistory)
In 1915, the first voice was transmitted across the continent by the NAA naval radio station in Arlington, Virginia, across New York to San Francisco, across the Atlantic to the Eiffel Tower in Paris. On November 2, 1920, radio station KDKA - Pittsburgh broadcast Harding-Cox election results and started a daily radio program.
In 1927, the North American and European radio communications system was established, and three years later, South America could be connected. Until 1935, the first calls were made worldwide, using a combination of wired and wireless radio systems.
The birth of FM radio and radio today:
In 1933, Edwin Howard Armstrong invented frequency-modulated radio, or FM radio . FM waves have the advantage of limiting the interference of other electronic devices and the Earth's magnetic field. By 1936, all US transatlantic telephone communications transmitted to England and Paris all applied this method. Up to that point, both wired and wireless communication networks could connect the US with nearly 187 other points abroad.
Picture Howard and the Radio caught the first FM in the honeymoon with his wife.(photo taken in 1923, source: world.std)
Since then, radio technology has always been developed in an extremely fast way. In 1947, scientists at Bell Labs in New Jersey, USA invented transistors. And in 1954, Tokyo Telecommunications Engineering Corp. - precursor of Sony was the first company to produce mobile semiconductor radios.
Sony's first transistor station (Source: xtimeline)
In 1965, the world's first FM radio antenna system was built on the Empire State Building in New York, allowing private FM radio stations to broadcast from one source to several other receivers. together. This is also the radio model that is widely applied all over the world to this day.
Details of the antenna broadcast the first FM at the top of the Empire State building
(Photo taken around 1965, source: lnl.com)
Thus, from the first studies of the theory of electromagnetic waves, until very primitive signals such as an S by Morse code or a "hello" sentence passed between 2 points, we have found Today's series of modern radio stations with extremely rich and diverse news, news and entertainment programs.
Underneath all these successes is an endless effort by scientists, inventors to turn the impossible into possible, turn the wired communication into wireless. Thereby, creating the utility and a series of applications of wireless signal transmission method for many different fields.