Although radios may seem somehow obsolete today, considering the numerous audio devices available on the market, such as MP3 and portable media players, the radio has a very long and controversial history behind it, being one of the most important discoveries of its time and of the civilized world as we know it, together with the telephone and television.
What probably only few people know is that, even though the invention of the radio is granted to Guglielmo Marconi, there has been a great controversy regarding its “paternity”. Thus, in the history of radio and development of wireless telegraphy, several people claimed to have invented the radio, such as Jagadish Chandra Bose, the already mentioned Marconi (equipped ships with life-saving wireless communications, conducted a reported transatlantic radio communications experiments in 1901 and established the first commercial transatlantic radio service in 1907), Alexander Stepanovich Popov and Nikola Tesla (developed means to reliably produce radio frequency currents, publicly demonstrated the principles of radio, and transmitted long distance signals).
The reason why it's still not clear, up to this date, who is the actual inventor of the radio is the fact that the technology is a product of many different discoveries and developments. After all, it's a well-known fact that the radio couldn't have existed without the telegraph and telephone having been invented first.
What is it?
But to get a clearer picture, we must first define radio. Hence, radio is the transmission of signals, by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information is carried by systematically changing (modulating) some property of the radiated waves, such as amplitude, frequency, or phase.
When radio waves pass through an electrical conductor, the oscillating fields induce an alternating current in the conductor. This can be detected and transformed into sound or other signals that carry information. As you might have noticed already, radio can refer to either the electronic appliance that we listen with or the content listened to. But for the relevance of the radio's history, the content clearly prevails as importance.
Etymology
The radio's connection to the previous inventions (the telegraph and the telephone) can be noticed from its very etymology, as, originally, radio or radiotelegraphy was called “wireless telegraphy”, which was shortened to “wireless”. Radio, as a noun, appeared in a 1907 article by Lee de Forest and was adopted by the United States Navy in 1912, to become common by the time of the first commercial broadcasts in the US, in the 1920s.
Even though the term “wireless” has gained renewed popularity through the rapid growth of short-range computer networking (Wireless Local Area Network - WLAN, WiFi and Bluetooth), as well as mobile telephony (GSM and UMTS), today, the term “radio” often refers to the actual transceiver device or chip, whereas “wireless” refers to the system and/or method used for radio communication. Hence, one talks about radio transceivers and Radio Frequency Identification (RFID), but about wireless devices and wireless sensor networks.
Processes
Overseas radiotelegraphy service developed slowly, primarily because the initial radiotelegraph transmitter discharged electricity within the circuit and between the electrodes, which made it unstable, causing a high amount of interference.
The Alexanderson high-frequency alternator (a device that converts direct current into alternating current) and the De Forest tube resolved many of these early technical problems. Lee Deforest invented space telegraphy, the triode amplifier and the Audion. In the early 1900s, the great requirement for further development of radio was an efficient and delicate detector of electromagnetic radiation.
Lee De Forest provided that detector. It made it possible to amplify the radio frequency signal picked up by the antenna before application to the receiver detector; thus, much weaker signals could be utilized than had previously been possible. The result of Lee DeForest's work was the invention of amplitude-modulated or AM radio that allowed for a multitude of radio stations. The earlier spark-gap transmitters did not allow for this.
Short history
Many individuals - inventors, engineers, developers, businessmen - contributed to produce the modern idea of radio and thus the origins and 'invention' are multiple and controversial. Development from a laboratory demonstration to commercial utility spanned across several decades and required the efforts of many practitioners.
Twenty years after the telephone was invented and music was first sent down a telephone line, Guglielmo Marconi sent radio signals. Marconi (1874-1937) was born in Italy and studied at the University of Bologna. He was fascinated by Heinrich Hertz's earlier discovery of radio waves and realized that it can be used for sending and receiving telegraph messages, referring to it as “wireless telegraphs.”
Marconi's first radio transmissions, in 1896, were coded signals that were transmitted only about 1,6 km (a mile) away. Marconi realized that it held huge potential. He offered the invention to the Italian government but they turned it down. He moved to England, took out a patent, and experimented further. In 1898, he flashed the results of the Kingstown Regatta to the offices of a Dublin newspaper, thus making a sports event the first “public” broadcast.
The next year Marconi opened the first radio factory in Chelmsford, Essex and established a radio link between Britain and France. A link with the USA was established in 1901. In 1909 Marconi shared the Nobel prize in physics for his wireless telegraph. But Marconi's wireless telegraph transmitted only signals. Voice over the air, as we know radio today, came only in 1921. Marconi went on to introduce short wave transmission in 1922. He was not the first to invent the radio, however.
Four years before Marconi started experimenting with wireless telegraph, Nikola Tesla, a Croatian who moved to the USA in 1884, invented the theoretical model for radio. Tesla tried, with no success, to obtain a court injunction against Marconi in 1915. In 1943, the US Supreme Court reviewed the decision and Tesla became acknowledged as the inventor of the radio - even though he did not build a working radio.
The first public demonstration of wireless telegraphy took place in the lecture theater of the Oxford University Museum of Natural History on August 14, 1894, carried out by Professor Oliver Lodge and Alexander Muirhead. During the demonstration a radio signal was sent from the neighboring Clarendon laboratory building, and received by apparatus in the lecture theater.
In 1895 Alexander Stepanovich Popov built his first radio receiver, which contained a coherer. Further refined as a lightning detector, it was presented to the Russian Physical and Chemical Society on May 7, 1895. A depiction of Popov's lightning detector was printed in the Journal of the Russian Physical and Chemical Society the same year. Popov's receiver was created on the improved basis of Lodge's receiver, and originally intended for reproduction of its experiments. The first radio broadcasts have been aired in 1920, in the US, Europe and Argentina.
Developments
One of the first developments in the early 20th century (1900-1959) was that aircrafts used commercial AM radio stations for navigation. This continued until the early 1960s, when VOR systems finally became widespread. In the early 1930s, single sideband and frequency modulation were invented by amateur radio operators.
By the end of the decade, the first commercial modes were established. Radio was used to transmit pictures visible as television as early as the 1920s. Commercial television 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 22.5 V Battery".
In 1960, Sony introduced its 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 20 years, transistors replaced tubes almost completely except for very high-power uses.
By 1963, color television was being regularly transmitted commercially, 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. Digital transmissions began to be applied to broadcasting in the late 1990s.
Uses of the radio
Early uses of the radio were maritime and military. Today, radio takes many forms, including wireless networks and mobile communications of all types, as well as radio broadcasting. AM broadcast radio sends music and voice in the Medium Frequency radio spectrum, using amplitude modulation, while FM broadcast radio sends music and voice with higher fidelity, using frequency modulation. Due to its need for a wider bandwidth, FM is transmitted in Very High Frequency radio spectrum.
Radio is also used in field like telephony, television, navigation, radar (Radio Detection And Ranging), heating (microwave ovens, diathermy equipment, induction furnaces etc), amateur and unlicensed radio services, radio control (RC). But the 21st century radio developments that are very en vogue nowadays are digital audio broadcasting (DAB) and the Internet radio, as well as the HD Radio, a technology incorporated by numerous companies into their products.
Digital Audio Broadcasting (DAB), also known as Eureka 147, with its DAB+ and DMB variations, is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe, while the Internet radio consists of sending radio-style audio programming over streaming Internet connections: no radio transmitters need to be involved at any point in the process. Such devices have already been developed by large companies, such as Pure, Tangent, Roberts, Intempo, Sony, iRiver and Teac.
DAB was the first standard based on orthogonal frequency division multiplexing (OFDM) modulation technique, which since then has become one of the most popular transmission schemes for modern wideband digital communication systems. The first country to receive a wide range of stations via DAB was UK, several other European countries following, together with Australia.
Traditionally radio programs were broadcast on different frequencies via FM and AM, and the radio had to be tuned into each frequency. This used up a comparatively large amount of spectrum for a relatively small number of stations, limiting listening choice. DAB is a digital radio broadcasting system that through the application of multiplexing and compression combines multiple audio streams onto a single broadcast frequency called a DAB ensemble.
Within an overall target bit rate for the DAB ensemble, individual stations can be allocated different bit rates. The number of channels within a DAB ensemble can be increased by lowering average bit rates, but at the expense of the quality of streams. Error correction under the DAB standard makes the signal more robust but reduces the total bit rate available for streams. However, there's quite a lot of criticism brought against the DAB radio too, regarding the reception quality, signal delay, coverage, transmission cost, compatibility and power requirements.
HD Radio is a digital transmission system for audio broadcast stations, a proprietary trademark for iBiquity Digital Corporation's in-band on-channel (IBOC) technology. Although the company claims that HD Radio is just a brand name, the documents that it submitted to the FCC refer to it as “hybrid digital radio technology”.
Praised by its producer as approaching CD quality sound and offering reduction of both interference and static, the HD Radio is officially known as NRSC-5. Digital information is transmitted using COFDM with an audio compression algorithm called HDC with SBR (based upon MPEG-4 HE-AAC).
If digital signal reception is lost, the HD radio will revert to the analog signal, thereby providing seamless operation between the newer and older transmission methods. Alternatively, the HD Radio can revert to a more-robust ~20 kilobit per second stream. Datacasting is also possible, with metadata providing song titles or artist information. Competing systems include FmeXtra, DRM+ ( Digital Radio Mondiale) and CAM-D (Compatible AM-Digital).
Judging by the course of the radio's history, the only conclusion we could reach is that it won't be too long until new technologies will transform the radio again, as they have along the years. Numerous innovations are standing at the gates of today's technological world, waiting to make a change, and the radio will definitely not be spared.
