Editing History of radio (section)

==Audio transmission==

[[File:Reginald Fessenden, probably 1906.jpg|thumb|Reginald Fessenden (around 1906)]]

In the late 1890s, Canadian-American inventor [[Reginald Fessenden]] came to the conclusion that he could develop a far more efficient system than the spark-gap transmitter and coherer receiver combination.<ref>''The Continuous Wave'' by Hugh G. J. Aitken, 1985, p. 50.</ref><ref>Fessenden, Helen (1940), [https://babel.hathitrust.org/cgi/pt?id=uc1.b4540711&view=1up&seq=74 pp. 60–61, 76].</ref> To this end he worked on developing a high-speed alternator (referred to as "an alternating-current dynamo") that generated "pure sine waves" and produced "a continuous train of radiant waves of substantially uniform strength", or, in modern terminology, a  [[continuous wave|continuous-wave]] (CW) transmitter.<ref>{{patent|US|706737|patent: "Wireless Telegraphy"}}</ref> While working for the [[United States Weather Bureau]] on [[Cobb Island (Maryland)|Cobb Island]], Maryland, Fessenden researched using this setup for audio transmissions via radio. By fall of 1900, he successfully transmitted speech over a distance of about 1.6 kilometers (one mile),<ref name="experiments">"Experiments and Results in Wireless Telephony" by John Grant, ''The American Telephone Journal''. [https://babel.hathitrust.org/cgi/pt?id=mdp.39015057240221&view=1up&seq=111 Part I]: January 26, 1907, pp. 49–51; [https://babel.hathitrust.org/cgi/pt?id=mdp.39015057240221&view=1up&seq=147 Part II]: February 2, 1907, pp. 68–70, 79–80.</ref> which appears to have been the first successful audio transmission using radio signals.<ref>T. K. Sarkar, Robert Mailloux, Arthur A. Oliner, [[Magdalena Salazar Palma]], Dipak L. Sengupta, ''History of Wireless'', Wiley – 2006, p. 92</ref><ref>John W. Klooster, ''Icons of Invention – The Makers of the Modern World from Gutenberg to Gates'' – Vol. 1, Greenwood Press – 2009, p. 400</ref> Although successful, the sound transmitted was far too distorted to be commercially practical.<ref>Hugh G. J. Aitken, ''The Continuous Wave: Technology and American Radio, 1900–1932''. Princeton University Press. Princeton, New Jersey – 1985,  p. 61</ref> According to some sources, notably Fessenden's wife Helen's biography, on [[Christmas Eve]] 1906, [[Reginald Fessenden]] used an [[Alexanderson alternator]] and rotary [[spark-gap transmitter]] to make the first radio audio broadcast, from [[Ocean Bluff-Brant Rock, Massachusetts|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]].<ref>[https://archive.org/details/radioindustrysto00harvrich/page/190/mode/1up "The Early History of Radio in the United States"] by H. P. Davis, in ''The Radio Industry: The Story of its Development'', 1928, p. 190.</ref><ref>Helen M. Fessenden, ''Reginald Fessenden: Builder of Tomorrow'', New York: Coward-McCann, 1940</ref>

Around the same time American inventor [[Lee de Forest]] experimented with an [[arc converter|arc transmitter]], which unlike the discontinuous pulses produced by spark transmitters, created steady "continuous wave" signal that could be used for [[amplitude modulated]] (AM) audio transmissions. In February 1907 he transmitted electronic [[telharmonium]] music from his laboratory station in New York City.<ref>''Father of Radio'' by Lee de Forest, 1950, p. 225.</ref> This was followed by tests that included, in the fall, [[Eugenia Farrar]] singing "I Love You Truly".<ref>[https://babel.hathitrust.org/cgi/pt?id=mdp.39015020686641&view=1up&seq=60 ''I Looked and I Listened''] by Ben Gross, 1954, p. 48.</ref> In July 1907 he made ship-to-shore transmissions by radiotelephone—race reports for the Annual Inter-Lakes Yachting Association (I-LYA) Regatta held on [[Lake Erie]]—which were sent from the steam yacht ''Thelma'' to his assistant, Frank E. Butler, located in the Fox's Dock Pavilion on [[South Bass Island]].<ref>[https://archive.org/stream/electricalworld50newy#page/293/mode/1up "Reporting Yacht Races by Wireless Telephony"], ''Electrical World'', August 10, 1907, pp. 293–94. (archive.org)</ref>

===Broadcasting===
{{See also|Old-time radio|History of broadcasting|Radio broadcasting#History|AM broadcasting#History|FM broadcasting#History}}

The Dutch company ''Nederlandsche Radio-Industrie'' and its owner-engineer, [[Hanso Idzerda]], made its first regular entertainment radio broadcast over station [[PCGG]] from its workshop in [[The Hague]] on 6 November 1919. The company manufactured both transmitters and receivers. Its popular program was broadcast four nights per week using narrow-band FM transmissions on 670 metres (448&nbsp;kHz),<ref>[[:File:Soireé-Musicale.jpg|"Radio Soireé-Musicale"]] ''Nieuwe Rotterdamsche Courant'', 05 November 1919, p. 16</ref> until 1924 when the company ran into financial trouble.

Regular entertainment broadcasts began in [[Argentina]], pioneered by [[Enrique Telémaco Susini]] and his associates. At 9 pm on August 27, 1920, Sociedad Radio Argentina aired a live performance of Richard Wagner's opera ''Parsifal'' from the Coliseo Theater in downtown [[Buenos Aires]]. Only about twenty homes in the city had receivers to tune in this program.

On 31 August 1920 the ''[[Detroit News]]''  began publicized daily news and entertainment "Detroit News Radiophone" broadcasts, originally as licensed amateur station 8MK, then later as WBL and [[WWJ (AM)|WWJ]] in [[Detroit|Detroit, Michigan]].

Union College in Schenectady, [[New York (state)|New York]] began broadcasting on October 14, 1920, over [[WRUC|2ADD]], an amateur station licensed to Wendell King, an [[African-American]] student at the school.<ref name="Radio Broadcasting">{{cite web|url=http://w2uc.union.edu/RADIO_web.htm |title=Radio Broadcasting at Union College|publisher=W2UC.union.edu |author=Rowan Wakefield|date=February 1959|access-date=2009-07-22 |url-status=dead |archive-url=https://web.archive.org/web/20080515103959/http://w2uc.union.edu/RADIO_web.htm |archive-date=May 15, 2008}}</ref> Broadcasts included a series of Thursday night concerts initially heard within a {{convert|100|mi|adj=on}} radius and later for a {{convert|1000|mi|adj=on}} radius.<ref name="Radio Broadcasting"/><ref>{{cite web|title=From a Shed to the World Wide Web|publisher=Union College Magazine|access-date=2018-02-03 |url=https://muse.union.edu/newsarchives/1995/11/01/from-a-shed-to-the-world-wide-web/|date=1 November 1995}}</ref>

In 1922 regular audio broadcasts for entertainment began in the UK from the [[Guglielmo Marconi|Marconi]] Research Centre [[2MT]] at [[Writtle]] near [[Chelmsford, England]].

==== Wavelength and frequency  ====
In early radio, and to a limited extent much later, the transmission signal of the radio station was specified in meters, referring to the [[wavelength]], the length of the radio wave. This is the origin of the terms [[long wave]], [[medium wave]], and [[short wave]] radio.<ref>{{Cite web|title=Radio Waves and the Electromagnetic Spectrum|url=https://radiojove.gsfc.nasa.gov/education/lesson_plans/lesson4.pdf|website=radiojove}}</ref> Portions of the radio spectrum reserved for specific purposes were often referred to by wavelength: the [[40-meter band]], used for [[History of amateur radio|amateur radio]], for example. The relation between wavelength and frequency is reciprocal: the higher the frequency, the shorter the wave, and vice versa.

As equipment progressed, precise frequency control became possible; early stations often did not have a precise frequency, as it was affected by the temperature of the equipment, among other factors. Identifying a radio signal by its frequency rather than its length proved much more practical and useful, and starting in the 1920s this became the usual method of identifying a signal, especially in the United States. Frequencies specified in number of cycles per second (kilocycles, megacycles) were replaced by the more specific designation of [[hertz]] (cycles per second) about 1965.