History of radio
- 1 Origins and developments
- 2 20th century developments
- 3 21st century development
- 4 Exotic technologies
- 5 Television
- 6 See also
- 7 Further reading
- 8 External links
Origins and developments
The identity of the original inventor of radio, at the time called wireless telegraphy, is contentious. The key invention for the beginning of "wireless transmission of data using the entire frequency spectrum" [spark-gap radio] has been attributed to Nikola Tesla, Guglielmo Marconi, and Alexander Popov (possibly in that order).
Radio's prehistory (19th century)
In 1820, Hans Christian Ørsted discovered the relationship between electricity and magnetism in a very simple experiment. He demonstrated that a wire carrying a current was able to deflect a magnetized compass needle.
In 1831, Michael Faraday began a series of experiments in which he discovered electromagnetic induction. The relation was mathematically modelled by Faraday's law, which subsequently became one of the four Maxwell equations.
Faraday proposed that electromagnetic forces extended into the empty space around the conductor, but did not complete his work involving that proposal. The theoretical basis of the propagation of electromagnetic waves was first described in 1873 by James Clerk Maxwell in his paper to the Royal Society A Dynamical Theory of the Electromagnetic Field, which followed his work between 1861 and 1865.
In 1878 David E. Hughes realized the transmission and reception of radio waves when he noticed that his induction balance caused noise in the receiver of his homemade telephone. He demonstrated his discovery to the Royal Society in 1880 but was told it was merely induction.
It was Heinrich Rudolf Hertz who, between 1886 and 1888, validated Maxwell's theory through experiment, demonstrating that radio radiation had all the properties of waves (now called Hertzian waves), and discovering that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation.
Claims have been made that Murray, Kentucky farmer Nathan Stubblefield invented radio during the period of 1885–1892, but his devices seem to have worked by induction transmission rather than radio transmission.
In 1893 in St. Louis, Missouri, Tesla gave a public demonstration of "wireless" radio communication. Addressing the Franklin Institute in Philadelphia and the National Electric Light Association, he described in detail the principles of radio communication.  The apparatus that he used contained all the elements that were incorporated into radio systems before the development of the vacuum tube. Tesla was the first to apply the mechanism of electrical conduction to wireless practices. Also, He initially used sensitive electromagnetic receivers , unlike the less responsive coherers used by Marconi and other early experimenters.
A public demonstration of transmission and reception of radio waves used for communication was performed by the Russian physicist Alexander Popov at the Russian Physical and Chemical Society on May 7, 1895—which has since been celebrated in the Russian Federation as "Radio Day".
In 1896 Marconi was awarded a patent for radio with British Patent 12039, Improvements in Transmitting Electrical Impulses and Signals and in Apparatus There-for. This was recognised as the world's first patent for radio, though it used various earlier techniques of Tesla, and resembled the instrument demonstrated by Popov. In 1897 Marconi established the a radio station on the Isle of Wight, England. The same year in the U.S., Tesla applied for two key radio patents which were issued in early 1900. The U.S. Patent Office reversed its decision in 1904, awarding Marconi a patent for the invention of radio, possibly influenced by Marconi's financial backers in the States, who included Thomas Edison and Andrew Carnegie. Some believe this allowed the U.S. government to avoid having to pay the royalties that were being claimed by Tesla for use of his patents.
After the public demonstrations of radio communication that Tesla made in 1893, the principle of radio communication—sending signals through space to receivers—was publicized widely. The Telsa apparatus contained all the elements of radio systems used before the development of the vacuum tube.
On 19 August 1894, British physicist Sir Oliver Lodge demonstrated the reception of Morse code signalling using radio waves using a detecting device called a coherer, a tube filled with iron filings which had been invented by Temistocle Calzecchi-Onesti at Fermo in Italy in 1884. Edouard Branly of France and Alexander Popov of Russia later produced improved versions of the coherer. Popov, who was the first to develop a practical communication system based on the coherer, is usually considered by his own countrymen to have been the inventor of radio.
The Indian physicist, Jagdish Chandra Bose, demonstrated publicly the use of radio waves in November of 1894 in Calcutta, but he was not interested in patenting his work.  Bose ignited gunpowder and rang a bell at a distance using electromagnetic waves, proving that communication signals can be sent without using wires. Bose went to London on a lecture tour in 1896 and met Marconi, who was conducting wireless experiments for the British post office. Later in 1899 Bose announced his invention of the "iron-mercury-iron coherer with telephone detector" in a paper presented at Royal Society, London.
In 1895, Marconi sent a telegraph message without wires, but he didn't send voice over the airwaves; Reginald Fessenden, in 1900, accomplished that and made a weak transmission. On Christmas Eve, 1906, using his heterodyne principle, Fessenden transmitted the first radio broadcast in history from Brant Rock, Massachusetts. Ships at sea heard a broadcast that included Fessenden playing the song "O Holy Night" on the violin and reading a passage from the bible.
In 1909, Marconi, with Karl Ferdinand Braun, was also awarded the Nobel Prize in Physics for "contributions to the development of wireless telegraphy". However, Tesla's patent (number 645576) was reinstated in 1943 by the U.S. Supreme Court, shortly after his death. This decision was based on the fact that prior art existed before the establishment of Marconi's patent. Some believe the decision was also made for financial reasons, to allow the U.S. government to avoid having to pay damages that were being claimed by the Marconi Company for use of its patents during World War I (though, these people ignore Tesla's prior art).
Marconi opened a radio factory in Hall Street, Chelmsford, England in 1898, employing around 50 people. Around 1900, Tesla opened the Wardenclyffe Tower facility and advertised services. By 1903, the tower structure neared completion. Various theories exist on how Tesla intended to achieve the goals of this wireless system (reportedly, a 200 kW system). Tesla claimed that Wardenclyffe, as part of a World System of transmitters, would have allowed secure multichannel transceiving of information, universal navigation, time synchronization, and a global location system.
The first benefit to come from radio telegraphy was the ability to establish communication between coast radio stations and ships at sea. A company called "British Marconi" was established to make use of Marconi's and others' patents. This company along with its subsidiary American Marconi, had a stranglehold on ship to shore communication. It operated much the way American Telephone and Telegraph operated until 1983, owning all of its own equipment and refusing to communicate with non-Marconi equipped ships. Many inventions improved the quality of radio, and amateurs experimented with uses of radio, thus the first seeds of broadcasting were planted.
Wireless telegraphy using spark gap transmitters quickly became universal on large ships after the sinking of the RMS Titanic in 1912. The International Convention for the Safety of Life at Sea was convened in 1913 and produced a treaty requiring shipboard radio stations be manned 24 hours a day.
A typical high-power spark gap was a rotating commutator with six to twelve contacts per wheel, nine inches to a foot wide, driven by about 2000 volts DC. As the gaps made and broke contact, the radio wave was audible as a tone in a crystal set. The telegraph key often directly made and broke the 2000 volt supply. One side of the spark gap was directly connected to the antenna. Receivers with thermionic valves became commonplace before spark-gap transmitters were replaced by continuous wave transmitters.
Audio broadcasting (1915–Present)
The invention of the vacuum tube detector, invented by a team of Westinghouse engineers. On Christmas Eve, 1906, Reginald Fessenden (using his heterodyne principle) transmitted the first radio audio broadcast in history from Brant Rock, Massachusetts. Ships at sea heard a broadcast that included Fessenden playing O Holy Night on the violin and reading a passage from the Bible.
The first known radio news program was broadcast August 31, 1920 by station 8MK, the unlicensed predecessor of WWJ (AM) in Detroit, Michigan. Regular wireless broadcasts for entertainment commenced in 1922 from the Marconi Research Centre at Writtle near Chelmsford, England. Early radios ran the entire power of the transmitter through a carbon microphone.
While some early radios used some type of amplification through electric current or battery, through the mid 1920s the most common type of receiver was the crystal set. In the 1920s, amplifying vacuum tubes revolutionized both radio receivers and transmitters.
Inventions of the triode amplifier, generator, and detector enables audio radio. The invention of amplitude-modulated (AM) radio, so that more than one station can send signals (as opposed to spark-gap radio, where one transmitter covers the entire bandwidth of spectra) was pioneered by Reginald Fessenden and Lee de Forest.
Radio broadcasting beginnings
Charles David Herrold, an electronics instructor in San Jose, California constructed a broadcasting station in April 1909. It used spark gap technology, but modulated the carrier frequency with the human voice, and later music. The station "San Jose Calling" (there were no call letters), continued in an unbroken lineage to eventually become today's KCBS in San Francisco.
Herrold, the son of a Santa Clara Valley farmer, coined the terms "narrowcasting" and "broadcasting", respectively to identify transmissions destined for a single receiver such as that on board a ship, and those transmissions destined for a general audience. The term "broadcasting" had been used in farming to define the tossing of seed in all directions.
While Charles Herrold did not claim to be the first to transmit the human voice, he did claim to be the first to conduct "broadcasting". To facilitate the spreading of the radio signal in all directions, he designed omni-directional antennas, which he mounted on the rooftops of various buildings in San Jose. Herrold also claims the title as the first broadcaster to accept advertising, although advertising generally involves paid announcements. He exchanged publicity for a local record store for records to play on his station.
Westinghouse in Pittsburgh, Pennsylvania became the first US licensed commercial broadcasting station when it was granted call letters KDKA in October 1920. Their engineer Frank Conrad had been broadcasting from his own station since 1916. E.W. Scripps's WWJ in Detroit also claims priority, but they did not receive their commercial license until nearly a year later. Broadcasting was not yet supported by advertising. The stations owned by manufacturers and department stores were established to sell radios and those owned by newspapers to sell papers and express the opinions of the owners.
Westinghouse was brought into the patent allies group, General Electric, American Telephone and Telegraph, and Radio Corporation of America, and became a part owner of RCA. All radios made by GE and Westinghouse were sold under the RCA label 60% GE and 40% Westinghouse. ATT's Western Electric would build radio transmitters. The patent allies attempted to set up a monopoly, but they failed due to successful competition. Much to the dismay of the patent allies, several of the contracts for inventor's patents held clauses protecting "amateurs" and allowing them to use the patents. Whether the competing manufacturers were really amateurs was ignored by these competitors.
- Commercial (United States) or governmental (Europe) station networks
- Federal Radio Commission
- Federal Communications Commission
- Birth of the soap opera
- Race towards shorter waves and FM
FM radio was invented by Edwin H. Armstrong and patented in 1933. FM employs frequency modulation of the radio wave to minimize static and interference from electrical equipment and the atmosphere, in the audio program. W1XOJ was the first experimental FM radio station, granted a construction permit by the FCC in 1937.
In Europe the FM radio broadcast was introduced in Germany after World War II. In 1948 a new wavelength plan was set up for Europe at a meeting in Copenhagen. Because of the recent war, Germany (which was not even invited) was only given a few medium-wave frequencies, which are not very good for broadcasting. For this reason Germany began broadcasting on USW, "ultra short wave" (nowadays called VHF). After some amplitude modulation experience with VHF, it was realized that FM radio was a much better alternative for VHF radio than AM.
20th century developments
Developments in the 20th century:
- Aircraft used commercial AM radio stations for navigation. This continued through the early 1960s when VOR systems finally became widespread (though AM stations are still marked on U.S. aviation charts).
- In the early 1930s, single sideband and frequency modulation were invented by amateur radio operators. By the end of the decade, they were established commercial modes.
- Radio was used to transmit pictures visible as television as early as the 1920s. Standard analog transmissions started in North America and Europe in the 1940s.
- In 1954, Regency introduced a pocket transistor radio, the TR-1, powered by a "standard 22.5V Battery".
- In 1960, Sony introduced their first transistorized radio, small enough to fit in a vest pocket, and able to be powered by a small battery. It was durable, because there were no tubes to burn out. Over the next twenty years, transistors displaced tubes almost completely except for very high power, or very high frequency, uses.
- In 1963 color television was commercially transmitted, and the first (radio) communication satellite, TELSTAR, was launched.
- In the late 1960s, the U.S. long-distance telephone network began to convert to a digital network, employing digital radios for many of its links.
- In the 1970s, LORAN became the premier radio navigation system. Soon, the U.S. Navy experimented with satellite navigation, culminating in the invention and launch of the GPS constellation in 1987.
- In the early 1990s, amateur radio experimenters began to use personal computers with audio cards to process radio signals. In 1994, the U.S. Army and DARPA launched an aggressive, successful project to construct a software radio that could become a different radio on the fly by changing software.
- Digital transmissions began to be applied to broadcasting in the late 1990s.
Telex on Radio
Telegraphy did not go away on radio. Instead, the degree of automation increased. On land-lines in the 1930s, Teletypewriters automated encoding, and were adapted to pulse-code dialing to automate routing, a service called telex. For thirty years, telex was the absolute cheapest form of long-distance communication, because up to 25 telex channels could occupy the same bandwidth as one voice channel. For business and government, it was an advantage that telex directly produced written documents.
Telex systems were adapted to short-wave radio by sending tones over single sideband. CCITT R.44 (the most advanced pure-telex standard) incorporated character-level error detection and retransmission as well as automated encoding and routing.
For many years, telex-on-radio (TOR) was the only reliable way to reach some third-world countries. TOR remains reliable, though less-expensive forms of e-mail are displacing it. Many national telecom companies historically ran nearly pure telex networks for their governments, and they ran many of these links over short wave radio.
21st century development
- Early technology wars: Push or pull, streaming media or multicast
- Run your own station with live365 or almost like Geocities or Hotmail
Digital audio broadcasting (DAB) appears to be set grow in importance relative to FM radio for airborne broadcasts in several countries.
- Digital audio broadcasting
- XM Radio
- Sirius Satellite Radio
- Wireless LANs
- Personal area networks
- Digital Radio Mondiale
- Nationwide networks
- Satellite transmission
- Seifer, Marc J., "The Secret History of Wireless". Kingston, Rhode Island.
- Massie, Walter Wentworth, "Wireless telegraphy and telephony popularly explained". New York, Van Nostrand, 1908.