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URGENTE: quando è nata la modulazione AM e quando quella FM?
#1
chi lo sa risponda al più presto, grazieeeee :ridi:
e se lo sapete, sono state usate durante la 1° o la 2° guerra mondiale?
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«To see things thousands of miles away, things hidden behind walls and within rooms, things dangerous to come to, to draw closer, to see and be amazed. That’s Life.»

«Cos'è il genio? Fantasia, intuizione, colpo d'occhio e velocità d'azione.»
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#2
Che roba è? :lolA:
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#3
AM radio began with the first, experimental broadcast on Christmas Eve of 1906 by Canadian experimenter Reginald Fessenden, and was used for small-scale voice and music broadcasts up until World War I. San Francisco, California radio station KCBS claims to be the direct descendant of KQW, founded by radio experimenter Charles "Doc" Herrold, who made regular weekly broadcasts in San Jose, California as early as June 1909. On that basis KCBS has claimed to be the world's oldest broadcast station and celebrated its 100th anniversary in the summer of 2009. The great increase in the use of AM radio came late in the following decade as radio experimentation increased worldwide following World War I. The first licensed commercial radio services began on AM in the 1920s. XWA of Montreal, Quebec (later CFCF, now CINW) claims status as the first commercial broadcaster in the world, with regular broadcasts commencing on May 20, 1920. The first licensed American radio station was started by Frank Conrad, KDKA in Pittsburgh, Pennsylvania. Radio programming boomed during the "Golden Age of Radio" (1920s–1950s). Dramas, comedy and all other forms of entertainment were produced, as well as broadcasts of news and music.

FM broadcasting is a broadcast technology pioneered by Edwin Howard Armstrong that uses frequency modulation (FM) to provide high-fidelity sound over broadcast radio.

Even as the regenerative-circuit lawsuit continued, Armstrong was working on another momentous invention. While working in the basement laboratory of Columbia's Philosophy Hall, he created wide-band frequency modulation radio (FM). Rather than varying the amplitude of a radio wave to create sound, Armstrong's method varied the frequency of the wave instead. FM radio broadcasts delivered a much clearer sound, free of static, than the AM radio dominant at the time. (Armstrong received a patent on wide-band FM on December 26, 1933.[7]

In 1922, John Renshaw Carson of AT&T, inventor of Single-sideband modulation (SSB modulation), had published a paper in the Proceedings of the IRE arguing that FM did not appear to offer any particular advantage.[8] Armstrong managed to demonstrate the advantages of FM radio despite Carson's skepticism in a now-famous paper on FM in the Proceedings of the IRE in 1936,[9] which was reprinted in the August 1984 issue of Proceedings of the IEEE.[10]

Today the consensus regarding FM is that narrow band FM is not so advantageous in terms of noise reduction, but wide band FM can bring great improvement in signal to noise ratio if the signal is stronger than a certain threshold. Hence Carson was not entirely wrong, and the Carson bandwidth rule for FM is still important today. Thus, both Carson and Armstrong ultimately contributed significantly to the science and technology of radio. The threshold concept was discussed by Murray G. Crosby (inventor of Crosby system for FM Stereo) who pointed out that for wide band FM to provide better signal to noise ratio, the signal should be above a certain threshold, according to his paper published in Proceedings of the IRE in 1937.[11] Thus Crosby's work supplemented Armstrong's paper in 1936.

Armstrong conducted the first large scale field tests of his FM radio technology on the 85th floor of RCA's (Radio Corporation of America) Empire State Building from May 1934 until October 1935. However RCA had its eye on television broadcasting, and chose not to buy the patents for the FM technology.[12] A June 17, 1936, presentation at the Federal Communications Commission (FCC) headquarters made headlines nationwide. He played a jazz record over conventional AM radio, then switched to an FM broadcast. "[I]f the audience of 50 engineers had shut their eyes they would have believed the jazz band was in the same room. There were no extraneous sounds," noted one reporter. He added that several engineers described the invention "as one of the most important radio developments since the first earphone crystal sets were introduced."[13]

In 1937, Armstrong financed construction of the first FM radio station, W2XMN, a 40 kilowatt broadcaster in Alpine, New Jersey. The signal (at 42.8 MHz) could be heard clearly 100 miles (160 km) away, despite the use of less power than an AM radio station.[14]

RCA began to lobby for a change in the law or FCC regulations that would prevent FM radios from becoming dominant. By June 1945, the RCA had pushed the FCC hard on the allocation of electromagnetic frequencies for the fledgling television industry. Although they denied wrongdoing, David Sarnoff and RCA managed to get the FCC to move the FM radio spectrum from (42-50 MHz), to (88-108 MHz), while getting new low-powered community television stations allocated to a new Channel 1 in the 44-50 MHz range. In fairness to the FCC, the 42-50 MHz band was plagued by frequent tropospheric and E-layer stratospheric propagation which caused distant high powered stations to interfere with each other. The problem becomes even more severe on a cyclical basis when sunspot levels reach a maximum every 11 years and lower VHF band signals below 50 MHz can travel across the Atlantic Ocean or from coast to coast within North America on occasion. Sunspot levels were near their cyclical peak when the FCC reallocated FM in 1945. The 88-108 MHz range is a technically better location for FM broadcast because it is less susceptible to this kind of frequent interference. (Channel 1 eventually had to be deleted as well, with all TV broadcasts licensed at frequencies 54 MHz or higher, and the band is no longer widely used for emergency first responders either, those services having moved mostly to UHF.)

But the immediate economic impact of the shift, whatever its technical merit, was devastating to early FM broadcasters. This single FCC action would render all Armstrong-era FM receivers useless within a short time as stations were moved to the new band, and it also protected both RCA's AM-radio stronghold and that of the other major competing networks, CBS, ABC and Mutual. Armstrong's radio network did not survive the shift into the high frequencies and was set back by the FCC decision. This change was strongly supported by AT&T, because loss of FM relaying stations forced radio stations to buy wired links from AT&T.

Furthermore, RCA also claimed invention of FM radio and won its own patent on the technology. A patent fight between RCA and Armstrong ensued. RCA's momentous victory in the courts left Armstrong unable to claim royalties on any FM receivers, including televisions, sold in the United States. The undermining of the Yankee Network and his costly legal battles brought ruin to Armstrong, by then almost penniless and emotionally distraught. Eventually, after Armstrong's death, many of the lawsuits were decided or settled in his favor, greatly enriching his estate and heirs—but the decisions came too late for Armstrong himself to enjoy his legal vindication.
C'è un confine sottile tra uno sbaglio e un colpo di genio; purtroppo dovresti essere un genio per vederlo.

Sheldon Cooper

L'Italia è ancora come la lasciai, ancora polvere sulle strade,
ancora truffe al forestiero, si presenti come vuole.
Onestà tedesca ovunque cercherai invano,
c'è vita e animazione qui, ma non ordine e disciplina;
ognuno pensa per sé, è vano, dell'altro diffida,
e i capi dello stato, pure loro, pensano solo per sé


Johann Wolfgang von Goethe
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#4
dio santo google è stato fatto apposta
C'è un confine sottile tra uno sbaglio e un colpo di genio; purtroppo dovresti essere un genio per vederlo.

Sheldon Cooper

L'Italia è ancora come la lasciai, ancora polvere sulle strade,
ancora truffe al forestiero, si presenti come vuole.
Onestà tedesca ovunque cercherai invano,
c'è vita e animazione qui, ma non ordine e disciplina;
ognuno pensa per sé, è vano, dell'altro diffida,
e i capi dello stato, pure loro, pensano solo per sé


Johann Wolfgang von Goethe
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#5
Meso ti tromberei fin quando vuoi quando fai così :ridi:
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Le mie corse su Strava

«To see things thousands of miles away, things hidden behind walls and within rooms, things dangerous to come to, to draw closer, to see and be amazed. That’s Life.»

«Cos'è il genio? Fantasia, intuizione, colpo d'occhio e velocità d'azione.»
Cita messaggio
#6
Hartman Ha scritto:dio santo google è stato fatto apposta

eh cerco sempre su Google, solo non trovavo niente.. tu sai qualche trucco in più di me mi sa :lolB:
Instagram - 500px - LinkedIn
Le mie corse su Strava

«To see things thousands of miles away, things hidden behind walls and within rooms, things dangerous to come to, to draw closer, to see and be amazed. That’s Life.»

«Cos'è il genio? Fantasia, intuizione, colpo d'occhio e velocità d'azione.»
Cita messaggio
#7
:facepalm:
C'è un confine sottile tra uno sbaglio e un colpo di genio; purtroppo dovresti essere un genio per vederlo.

Sheldon Cooper

L'Italia è ancora come la lasciai, ancora polvere sulle strade,
ancora truffe al forestiero, si presenti come vuole.
Onestà tedesca ovunque cercherai invano,
c'è vita e animazione qui, ma non ordine e disciplina;
ognuno pensa per sé, è vano, dell'altro diffida,
e i capi dello stato, pure loro, pensano solo per sé


Johann Wolfgang von Goethe
Cita messaggio
#8
Matte 92 Ha scritto:eh cerco sempre su Google, solo non trovavo niente.. tu sai qualche trucco in più di me mi sa :lolB:

l'inglese? :p:lolA::facepalm:
"Nel tempo dell'inganno universale, dire la verità è un atto rivoluzionario" (G. Orwell).

"L'inferno dei viventi non è qualcosa che sarà; se ce n'è uno, è quello che è già qui, l'inferno che abitiamo tutti i giorni, che formiamo stando insieme. Due modi ci sono per non soffrirne. Il primo riesce facile a molti: accettare l'inferno e diventarne parte fino al punto di non vederlo più. Il secondo è rischioso ed esige attenzione e apprendimento continui: cercare e saper riconoscere chi e cosa, in mezzo all'inferno, non è inferno, e farlo durare, e dargli spazio." (Italo Calvino, Le Città Invisibili)
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#9
ma neanche

bastava scrivere

am radio

dopodichè ti saltava fuori la pagina "am broadcasting"

sulla base dell'esperienza recente scrivevi "fm broadcasting" dopodichè passavi alla pagina dell'inventore, tiravi fuori le parti con le date ed era tutto fatto


menti superiori :lolA:
C'è un confine sottile tra uno sbaglio e un colpo di genio; purtroppo dovresti essere un genio per vederlo.

Sheldon Cooper

L'Italia è ancora come la lasciai, ancora polvere sulle strade,
ancora truffe al forestiero, si presenti come vuole.
Onestà tedesca ovunque cercherai invano,
c'è vita e animazione qui, ma non ordine e disciplina;
ognuno pensa per sé, è vano, dell'altro diffida,
e i capi dello stato, pure loro, pensano solo per sé


Johann Wolfgang von Goethe
Cita messaggio
#10
Non è che serva l'inglese... :occhio:
Cronologia della radio - Wikipedia
Invenzione della radio - Wikipedia :lolA:
Peraltro come si può vedere stabilire la paternità e la data di nascita della AM non è una delle cose più semplici...
"Il governissimo come è stato fatto in Germania qui non è attuabile." (Enrico Letta, 8 aprile 2013). :buah:

La mia stazioncina meteo online (versione "quasi" definitiva)... Smile
http://rieticentrometeo.altervista.org

Terminillo.ORG Smile
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