prehistory of radio (19th century)
In 182, the relationship was discovered between and in a very simple experiment. He showed that the current carried by wires could deflect the magnetized compass needle. In 1831, he began a series of experimental electromagnetic induction, which was mathematically shaped by Faraday's law, and later became one of the four.
Faraday proposed that the electromagnetic force extend to the empty space near the conductor, but did not complete his work to intervene in that proposal. The theoretical basis of electromagnetic wave propagation was first described in 1873 by a dynamic theory of electromagnetic field in royal society in his paper, which followed his work between 1861 and 1865.1878. Hughes experienced the transmission and reception of radio waves when he noticed the noise caused by his inductive balance in his receiver. In 188, he showed his discovery to the royal society but told it was only inductive.
it was in 1886 and 1888 that Maxwell's theory was confirmed. Through experiments, it was shown that radio radiation had all the products of waves (now called Hertzian waves), and it was found that electromagnetic equations could be re-formed into partial differential equations called wave equations. It was required to put forward that Murray, a Kentucky farmer Nathan Stubblefield, was invented in the period of 1885-1892, but his equipment seemed to be.
the wireless starting point
was in St. Louis Tesla gave a public demonstration of "wireless" radio communication. Speaking at Franklin College in Philadelphia and the National Electric Association, he described in detail the principles of radio communication. [1] The appliance he used contains all the elements of the merged radio system before its development. Tesla is an application mechanism for electronic conduction to wireless practice. Moreover, he initially used the sensitive electromagnetic receiver [2], which was different from the less sensitive coherers used by Marconi and other early experimenters. The transmission of radio waves and a public demonstration of the reception were used for communication by Russian physicists Alexander? Popov celebrated the Union in Russia as "Radio Day" on May 7, 1895 in the Russian physical and chemical society.
in 1896, Marconi was granted a patent for radio and British 1239, which was improved in transmitting electronic impulses and signals and in appliances. Therefore, this was recognized as the first patent in the world for radio, although it used various earlier technologies of Tesla and similar instruments were displayed by Popov. Marconi established a radio station in 1897, and in the same year in U. S 。 Tesla applied for two key radio patents issued as early as 19.u. S 。 In 194, the Patent Office overturned its judgment and granted Marconi a patent for the invention of radio, which was possibly influenced by Marconi's financial backers, including Thomas Edison, and some believed that this allowed U. S 。 The government avoided having to pay the royalty who was asked by Tesla for the use of his patent.
radio communication
after Tesla made a public demonstration of radio communication in 1893, the principle of signals sent by radio communication was widely publicized through space receivers. Telsa appliances contain all the elements of the radio system that were used in vacuum tubes before the development.
On August 19th, 1894, Mr. Oliver, a British physicist, showed a reception in Morse code to signal the use of radio waves, using a found device called a coherer, and the tube was filled with debris Temistocle Calzecchi-Onesti in Fermo in Italy in 1884. Edouard Branly France and Alexandria? Popov coherer's Russia later led to an improved version. Popov, who developed a practical communication system according to Cohen, is generally regarded as the inventor of radio by his own villagers.
an Indian physicist, Jagdish Chandra Bose, publicly demonstrated the use of radio waves in Calcutta in November 1894, but he was not interested in patenting his work. [3] Bose was ignited by gunpowder and rang the bell at a distance using electromagnetic waves, which proved that communication signals could be sent without using wires. Bose took part in a lecture tour to London in 1896 and met Marconi, doing a wireless experiment for the British post office. Later, in 1899, Bose announced that "coherer's invention of molten steel, silver steel and telephone detector" was introduced in the paper in Royal Society, London.
in 1895, Marconi sent the message of A communication machine, but he didn't send sound on the radio waves. Reginald Fessenden, 19, completed that and made a weak transmission. On Christmas Eve, in 196, using his heterodyne principle, Fessen transmitted the first radio broadcast in history from Brandt Rock, Massachusetts. Ships at sea heard a song including Fessen playing "Radio O Holy Night" on the violin and reading a passage from the Bible.
In 199, Marconi, together with, was awarded the Nobel Prize for "contribution to the development of wireless telegraph" in physics. However, Tesla's patent (number 645576) was restored in 1943 by U. S 。 The Supreme Court, after his death. This decision is based on the fact that avant-garde art existed before Marconi's patent was created. Some believe in the decision and have been made to allow u for financial reasons. S 。 The government avoided having to pay for the damage caused by the Marconi Company's request for the use of its patents during World War I (though, this people ignored Tesla's avant-garde art).
Radio Factory
Marconi opened a radio factory in Hall Street, Chelmsford, England in 1898, employing about 5 people. Nearby, in 19, Tesla opened the Wardenclyffe tower facilities and advertising services. From 193, the tower structure was nearing completion. Various theories exist about how Tesla intends to achieve the goal of this wireless system (reportedly, a 2 kW system). Tesla claims that Wardenclyffe, as a part of the transmitter world system, will allow information, universal navigation, time synchronization, and a global positioning system for secure multi-channel transmission.
blank wireless telegraphy (1896–192)
The first benefit from the radio telecommunication law is the ability to establish communication between coastal radio stations and ships at sea. The company told "Britain" to set up Marconi and others. The company, together with its assistant, has a stranglehold in Marconi, USA, to support communication on board. It operated the way the American telephone and communication machine operated until 1983, owning all its own equipment and refusing to communicate with non-Marconi to equip the ship. Many inventions improved the quality of radios, and enthusiasts experimented with the use of radios, so the first seed of broadcasting was planted.
The use of spark gap transmitters in wireless telegraphy quickly became common. After the sinking of a large ship, the RMS force was extremely great. In 1912, the international conference was held for the safety of life at sea in 1913, and the production treaty required the ship's radio station to provide personnel 24 hours a day.
A typical powerful spark gap is a rotating commutator connecting each wheel with six to twelve, nine inches wide for one foot, and driving Volt DC about 2 years ago. Because the blank connects and breaks the connection, the radio wave is audible because the breath gathers in the crystal. The telegraph key was made and often directly broke the 2 volt supply. One side of the spark gap is directly connected to the antenna. The valves of receivers and hot electrons became common before the blank transmitter was replaced by the continuous wave transmitter.
Audio-visual Broadcasting (1915-Gift)
Invented the vacuum tube detector, and the team invented Westinghouse Electric Engineer. On Christmas Eve, in 196, Reginald Fessenden (using his heterodyne principle) transmitted the first radio audio-visual broadcast. Historically, ships at sea from Brandt Rock, Massachusetts heard the broadcast including Fessenden playing O Holy Night on the violin and reading a passage.
The first known radio news program was broadcast. In 192, by station 8MK, the unlicensed predecessor WWJ (in the morning), regular radio broadcasting began for entertainment. In 1922, from the research center in Writtle in nearby Chelmsford, England, the early radio ran the whole power of the transmitter through the carbon microphone.
When some early radios used some types of amplification through current or battery, the most similar type of receiver in the middle 192s was crystal collection. In the 192s, the amplification vacuum tube revolutionized two radio receivers and transmitters.
The invention of triode amplifier, generator and detector enabled audio-visual radios. Invent (morning) radio so that more than one station may send signals (as opposed to causing blank radios, one transmitter reports the entire bandwidth of the spectrum) for early work in Reginald Fessenden and Li? De Forest.
the starting point of radio broadcasting
Charles? David Herrold, an electronic counselor in San Jose, California, built a radio station in April 199. It uses spark gap technology, but adjusts carrier frequency to human voice, and the latest music. The resident "San Jose Call" (no radio call sign) continued in the intact descendants and eventually became KCBS in San Francisco today.
Herold, the son of A, a farmer in Santa Clara Valley, cast "narrowcasting" and "broadcast", respectively recognizing that transmissions are destined to be a unique receiver, such as that on the ship, and those transmissions are destined to be ordinary viewers. The stipulation that "broadcasting" was used in farming defined throwing seeds in all directions.
when Charles? Herrold didn't claim to be a transmitter's voice, he claimed to be a "broadcast". Promoting the spread of radio signals in all directions, he designed omni-directional antennas, and he boarded roofs of various buildings in San Jose. Herrold also won the title and accepted it as the first broadcaster, although advertising generally involves paid announcements. He exchanged propaganda for a local record store to make records play in his residence.
Westinghouse Electric in Pittsburgh, Pennsylvania became the first American licensed commercial radio station when it was awarded the radio call sign KDKA in October 192. Their engineers frankly broadcast from his own station since 1916. E 。 W 。 Scripps' WWJ was in Detroit and claimed priority, but they didn't accept their business license until almost a year later. Broadcasting is not supported by advertising. Stations are owned by manufacturers and department stores to sell radios and those owned by newspapers to sell newspapers and express the views of owners.
Westinghouse was led into the patent alliance group, American telephone and communication machine, and Radio Corporation America, and became the partial owner of RCA. All radios made by GE and Westinghouse were sold under RCA label 6% GE and 4% Westinghouse. ATT's western electric conference builds radio transmitter. Patent franchises tried to set up exclusivity, but they failed due to successful competition. For patent allies, several frustrated contracts have held entries for inventors' patents to protect "enthusiasts" and give them access to patents. Whether the makers of competition are really enthusiasts is ignored by these competitors.
Business (USA) or government (government) resident network
Federal Radio Commission
Federal Telecommunications and Transportation Commission
Soap operas
Race to Short Wave and FM
FM Radio
FM Radio was invented and patented in 1933. FM use was minimized static and interfered from electrical equipment and the atmosphere in audio-visual programs. W1XOJ is the first experimental FM station, which was granted the construction license by FCC in 1937.
Europe
After FM radio broadcasting was introduced in Europe in World War II, in 1948, a new wavelength plan was set for the conference. Due to the recent war, it was not even invited. Germany (only given several media to wave frequencies, not very good for broadcasting). So Germany began broadcasting in USW, "ultrashort wave" (now called VHF). After some experience with VHF, it is realized that FM radio is a better choice for VHF radio than in the morning.
Development in the 2th century
Development in the 2th century:
Business morning radio was used for navigation. This continued through the early 196s when the VOR system finally became universal (the morning station was still marked in U .. S 。 Aviation chart).
in the early days