Audion: Difference between revisions

| publisher = American Institute of Electrical and ElectronicElectronics Engineers

| url = https://earlyradiohistorybabel.ushathitrust.org/cgi/1907audpt?id=uiug.htm30112089533605&view=1up&seq=356

| access-date = JanuaryMarch 730, 20132021}} The link is to a reprint of the paper in the ''Scientific American Supplement'', NoNos. 1665 and 1666, November 30, 1907 and December 7, 1907, p.348-350, copiedand on Thomas H354-356. White's [https://earlyradiohistory.us/ United States Early Radio History] website</ref><ref name="Godfrey">{{cite encyclopedia

| first = Donald G.

| encyclopedia = Historical Dictionary of American Radio

| isbn = 9780313296369

| first = Sōgo

| encyclopedia = Newnes Dictionary of Electronics, 4th Ed.

| publisher = Newnes

| access-date = January 7, 2013}}</ref><ref name="Hijiya">{{cite book

| first = James A.

| isbn = 0934223238}}</ref><ref name="Lee">{{cite book

| first = Thomas H.

| isbn = 0521835267}}</ref><ref name="Hempstead">{{cite book

| isbn = 1579584640}}</ref> consisting of an evacuated [[glass tube]] containing three [[electrode]]s: a heated [[Electrical filament|filament]] (the cathode, made out of [[tantalum]]), a [[control grid|grid]], and a [[Plate electrode|plate]] (the anode).<ref name="Godfrey" /> It is important in the [[history of technology]] because it was the first widely used electronic device which could [[amplifier|amplify]];.<ref aname="Godfrey" small/> electricalA signallow appliedpower tosignal at the grid could control amuch largermore currentpower flowing fromin the filament to plate.<ref name="Godfrey" /><ref name="Newnes" />circuit.

The original triode AudionAudions had more [[Gas-filled tube|residual gas in the tube]] than later versions and [[vacuum tube]]stubes; the extra residual gas limited the [[dynamic range]] and gave the Audion non-linear characteristics and erratic performance.<ref name="Okamura" /><ref name="Lee" /> Originally developed as a radio receiver [[detector (radio)|detector]]<ref name="De Forest" /> by adding a grid electrode to the [[Fleming valve]], it found little use until its amplifying ability was recognized around 1912 by several researchers,<ref name="Lee" /><ref name="Nebeker">{{cite book

|title=Some Recent Developments in the Audion Receiver

|journal=Proceedings of the IRE

|volume=3

|number=9

}}. Republished as {{cite journal

|last=Armstrong

|first=E. H.

|author-link=Edwin Howard Armstrong

|title=Some Recent Developments in the Audion Receiver

|journal=Proceedings of the IEEE

|volume=85

|number=4

|url=http://www.ieee.org/documents/00573757.pdf

|doi=10.1109/jproc.1997.573757}}</ref> The many practical applications for amplification motivated its rapid development, and the original Audion was superseded within a few years by improved versions with a higher vacuum.<ref name="Lee" /><ref name="Nebeker" />

[[Image:Audion receiver.jpg|thumb|One of the earliestAn Audion [[radio receivers, constructedreceiver]] by De[[Lee de Forest|de in 1914Forest]]. The Audion tubes were mounted upside down, withto prevent the delicate filament hanging down, to prevent itfilaments from sagging and touching the gridgrids. This wasreceiver aprovided detectorthe (rectifier)ability andto twochoose stageoperation [[audioof amplifier]]either unit;one of the radiotwo signalprovided camedetector from a separate "tuner" unittubes.]]

It had been known since the middle of the 19th century that gas flames were [[Electrical conduction|electrically conductive]], and early wireless experimenters had noticed that this conductivity was affected by the presence of [[Radio frequency|radio waves]]. De Forest found that gas in a partial [[vacuum]] heated by a conventional lamp filament behaved much the same way, and that if a wire were wrapped around the glass housing, the device could serve as a detector of radio signals. In his original design, a small metal plate was sealed into the lamp housing, and this was connected to the positive terminal of a 22&ndash;volt22–volt battery via a pair of headphones, the negative terminal being connected to one side of the lamp filament. When wireless signals were applied to the wire wrapped around the outside of the glass, they caused disturbances in the current which produced sounds in the headphones.

This was a significant development as existing commercial wireless systems were heavily protected by [[patent]]s; a new type of detector would allow Dede Forest to market his own system. He eventually discovered that connecting the antenna circuit to a third electrode placed directly in the space current path greatly improved the sensitivity; in his earliest versions, this was simply a piece of wire bent into the shape of a [[Gridiron (cooking)|grid-irongridiron]] (hence "''grid"'').

De Forest and everybody else at the time greatly underestimated the potential of his originalgrid deviceAudion, imagining it to be limited to mostly military applications. It is significant that hede Forest apparently neverdid not sawsee its potential as a [[long distance calling|telephone repeater amplifier]] at the time he filed the patent claiming it, even though he had previously patented amplification devices and crude electromechanical ''note magnifiers'' had been the bane of the telephone industry for at least two decades. (Ironically, in the years of patent disputes leading up to World War I, it was only this "loophole" that allowed vacuum triodes to be manufactured at all since none of Dede Forest's patentsgrid Audion patent did specificallynot mentionedmention this application).

| footer = ''(left)'' The first prototype Audion with the grid (zigzag wires) between the filament and plate.<ref name="RadioNews">{{cite journal | last = Dede Forest | first = Lee | title = Evolution of the Vacuum Tube | journal = Radio News | volume = 9 | issue = 11 | pages = 990 | publisher = Experimenter Publications |date=May 1930 | url = http://www.americanradiohistory.com/Archive-Radio-News/30s/Radio-News-1930-05-R.pdf | access-date = August 3, 2014}}</ref> ''(right)'' Later design of an audion tube. The grid and plate are in two parts on either side of the central filament. In both these tubes the filament is burned out.

De Forest was granted a patent for his early two-electrode [[diode]] version of the Audion on November 13, 1906 ({{US patent|841386}}), and the "triode" (three-electrode) version was patented in 1908 ({{US patent|879532}}). De Forest continued to claim that he developed the Audion independently from [[John Ambrose Fleming]]'s earlier research on the [[thermionic valve]] (for which Fleming received Great Britain patent 24850 and the American [[Fleming valve]] patent {{US patent|803684}}), and Dede Forest became embroiled in many radio-related patent disputes. De Forest was famous for saying that he "didn't know why it worked, it just did".{{citation needed|date=July 2017}}

He always referred to the vacuum triodes developed by other researchers as "Oscillaudions", although there is no evidence that he had any significant input to their development. It is true that after the invention of the true vacuum triode in 1913 (see below), Dede Forest continued to manufacture various types of radio transmitting and receiving apparatus, (examples of which are illustrated on this page). However, although he routinely described these devices as using "Audions", they actually used high-vacuum triodes, using circuitry very similar to that developed by other experimenters.

In 1914, [[Columbia University]] student [[Edwin Howard Armstrong]] worked with professor [[John Harold Morecroft]] to document the electrical principles of the Audion. Armstrong published his explanation of the Audion in ''[[Electrical World]]'' in December 1914, complete with circuit diagrams and [[oscilloscope]] graphs.<ref name="Armstrong-audion">{{cite journal

|last=Armstrong

|first=E. H.

|author-link=Edwin Howard Armstrong

|title=Operating Features of the Audion

|journal=Electrical World

|volume=64

|number=24

|url=https://books.google.com/books?id=6WgfAQAAMAAJ&pg=PA1149

|pages=1149–1152

|date=December 12, 1914 }}</ref> In March and April 1915, Armstrong spoke to the [[Institute of Radio Engineers]] in New York and Boston, respectively, presenting his paper "Some Recent Developments in the Audion Receiver", which was published in September.<ref name="Armstrong1915" /> A combination of the two papers was reprinted in other journals such as the ''Annals of the New York Academy of Sciences''.<ref name="Armstrong-audion" /> When Armstrong and Dede Forest later faced each other in a dispute over the [[Regenerative circuit|regeneration]] patent, Armstrong was able to demonstrate conclusively that Dede Forest still had no idea how it worked.<ref name="Lee" /><ref>{{cite book |url=https://books.google.com/books?id=3iIOAAAAQAAJ&pg=PA178 |pages=178–184 |last=McNicol |first=Donald Monroe |title=Radio's Conquest of Space the Experimental Rise in Radio Communication |publisher=Taylor & Francis |year=1946}}</ref>

The problem was that (possibly to distance his invention from the Fleming valve) Dede Forest's original patents specified that low-pressure gas inside the Audion was essential to its operation (Audion being a contraction of "Audio-Ion"), and in fact early Audions had severe reliability problems due to this gas being adsorbed by the metal electrodes. The Audions sometimes worked extremely well; at other times they would barely work at all.

As well as Dede Forest himself, numerous researchers had tried to find ways to improve the reliability of the device by stabilizing the partial vacuum. Much of the research that led to the development of true vacuum tubes was carried out by [[Irving Langmuir]] in the [[General Electric]] (GE) research laboratories.

[[Image:Early triode vacuum tubes.jpg|thumb|upright=1.24|Audions and early triodes developed from them, 1918.
<br /ul>

<li>''Bottom row (D):'' De Forest Audions<br and oscillaudions</li>

<li>''Third row (C):'' Pliotrons, developed at [[General Electric]] by Langmuir<br /li>

<li>''Second row (B):'' triodes developed at [[Western Electric]] which bought the rights from Dede Forest in 1913. These were used in telephone [[repeater]]s which made possible the first transcontinental telephone line in 1915.<br /li>

<li>''Top row (A):'' French triodes. The French government gained the right to manufacture Audions in 1912 when Dede Forest failed to renew his French patents for lack of $125.]]</li>

He soon realized that his "vacuum" Audion had markedly different characteristics from the Dede Forest version, and was really a quite different device, capable of linear amplification and at much higher frequencies. To distinguish his device from the Audion he named it the "Pliotron", from the Greek ''plio'' (more or extra, in this sense meaning [[gain (electronics)|gain]], more signal coming out than went in).

[[File:1973 airmail stamp C86.jpg|thumb|1973 postage stamp honoring Dede Forest's audion]]

* {{cite court

* {{citation |first=Sungook |last=Hong |title=Wireless: From Marconi's Black-box to the Audion |year=2001 |publisher=MIT Press |isbn=9780262082983 |url=https://books.google.com/books?id=UjXGQSPXvIcC&pg=PA225 |ref=none}}

* ''Where Good Ideas Come From'', Chapter V, Steven Johnson, Riverhead Books, (2011).

* [https://web.archive.org/web/20121010212743/http://digitalgallery.nypl.org/nypldigital/dgkeysearchdetail.cfm?trg=1&strucID=51420&imageID=99555&total=7075&num=20&word=col_id%3A187&s=1&notword=&d=&c=&f=&k=0&lWord=&lField=&sScope=images&sLevel=&sLabel=%26quot%3BThe%20Pageant%20of%20America%26quot%3B%20Photograph%20Archive&imgs=20&pos=34&e=w 1906 photograph of the original Audion tube, from New York Public Library Digital Gallery]

* {{Cite web |last=Lewis |first=Tom |date=1991 |title=Telephone History - Empire of The Air: The Men Who Made Radio |url=http://www.privateline.com/TelephoneHistory3/empireoftheair.html |url-status=dead |archive-url=https://web.archive.org/web/20140511182508/http://www.privateline.com/TelephoneHistory3/empireoftheair.html |archive-date=May 11, 2014 |website=Privateline.com}}

* http://www.britannica.com/EBchecked/topic/1262240/radio-technology/25131/The-Fleming-diode-and-De-Forest-Audion

* {{citation |url=http://www.ieee.org/publications_standards/publications/proceedings/langmuir.pdf |title=The Pure Electron Discharge and Its Applications in Radio Telegraphy and Telephony |journal=Proceedings of the IEEE |volume=85 |issue=9 |pages=1496&ndash;15081496–1508 |date=September 1997 |orig-year=1915 |first=Irving |last=Langmuir |author1-link=Irving Langmuir |doi=10.1109/jproc.1997.628726 |s2cid=47501618 |ref=none}}{{dead link|date=July 2024|bot=medic}}{{cbignore|bot=medic}}. Reprint of {{citation |first=Irving |last=Langmuir |author1-link=Irving Langmuir |title=The Pure Electron Discharge and Its Applications in Radio Telegraphy and Telephony |journal=Proceedings of the IRE |volume=3 |issue=3 |pages=261–293 |date=September 1915 |url=https://books.google.com/books?id=AF0AAAAAMAAJ&pg=PA261 |ref=none |doi=10.1109/jrproc.1915.216680}}. (Includes comments from Dede Forest.)

* [https://earlyradiohistorybabel.ushathitrust.org/cgi/1907audpt?id=uiug.htm30112089533605&view=1up&seq=356 The Audion: A new Receiver for Wireless Telegraphy], Lee de Forest, Scientific American Supplement No. 1665, November 30, 1907, pages 348-350, Scientific American Supplement No. 1666, December 7, 1907, page 354–356.

* [http://120years.net/wordpress/the-audion-pianolee-de-forestusa1915/ Lee Dede Forest's Audion Piano on '120 years Of Electronic Music']

* https://books.google.com/books?id=YEASAAAAIAAJ&pg=PA166 Dede Forest and Armstong debate

* {{cite journal |last=Cole |first=A. B. |title=Practical Pointers on the Audion |journal=QST |pages=41&ndash;4441–44 |date=March 1916 |quote=The Audion Amplifier Bulb is entirely different from the Audion Detector Bulb in construction and vacuum. [page 43] |url=https://en.wikisource.org/wiki/QST/March_1916/Practical_Pointers_on_the_Audion}}

*: Also page 43 stating,

*:: Regular Audion Detector Bulbs are not adapted for the reception of continuous waves, because the vacuum is not correct for the purpose and because the filaments must be operated at such a high intensity that they give very short service, making them unnecessarily expensive.

*: Also page 44 stating,

*:: BLUE DISCHARGE OF GLOW

*::  This appears in some Audion Bulbs and not in others. If allowed to persist, the vacuum automatically increases. For this reason the glow should not be allowed to appear and certainly not to continue, as the vacuum may rise to a very high value, requiring very high voltage in the “B” battery.