Editing Spark-gap transmitter (section)

===Quenched-spark transmitters===
<gallery mode="packed" heights="140">
File:Telefunken ship radio room 1919.jpg|Ship radio room with 1.5&nbsp;kW Telefunken quenched-spark transmitter
File:Ship spark transmitter tuned circuit 1921.jpg|Tuned circuit of transmitter. ''(top)'' quenched gap, ''(center)'' oscillation transformer, Leyden jars
File:Quenched spark gap 1915.jpg|Quenched spark gap from transmitter, left. The handle turns a screw which puts pressure on the stack of cylindrical electrodes, allowing the gap widths to be adjusted.
File:Quenched spark gap - cutaway drawing.png|Cross section of portion of quenched spark gap, consisting of metal disks ''(F)'' separated by thin insulating mica washers ''(M)'' to make multiple microscopic spark gaps ''(S)'' in series
File:Powerful spark gap transmitter.png|A powerful quenched-spark transmitter in Australia. The 6 cylinders in front of the Leyden jars are the quenched spark gaps.
</gallery>

{{multiple image
| align= right
| direction= vertical
| image1= Spark-gap transmitter current waveforms.png
| caption1= Ordinary inductively coupled transmitter
| image2= Spark-gap transmitter current waveforms - quenched gap.png
| caption2= Quenched-spark transmitter<ref name="Leggett2"/>
| footer =
}}
The inductively-coupled transmitter had a more complicated output waveform than the non-syntonic transmitter, due to the interaction of the two resonant circuits. The two magnetically coupled tuned circuits acted as a [[Oscillation|coupled oscillator]], producing [[beat frequency|beats]] ''(see top graphs)''. The oscillating radio frequency energy was passed rapidly back and forth between the primary and secondary resonant circuits as long as the spark continued.<ref name="Leggett1">{{cite journal
| last1= Leggett
| first1= Bernard John
| title= Wireless Telegraphy, with special reference to the quenched-spark system
| journal= Nature
| volume= 107
| issue= 2691
| date= 1921
| pages= 51–55
| url= https://books.google.com/books?id=b843AAAAMAAJ&q=two+oscillations&pg=PA51
| doi= 10.1038/107390b0
| bibcode= 1921Natur.107..390.
| hdl= 2027/mdp.39015063598398
| s2cid= 4075587
| hdl-access= free
}}</ref><ref name="Beauchamp3"/><ref name="Huurdeman3">[https://books.google.com/books?id=SnjGRDVIUL4C&pg=PA271&dq=Wien+telefunken+squenched Huurdeman, Anton (2003) ''The Worldwide History of Telecommunications'', p. 271-272]. This author misspells the word "quenched" as "squenched"</ref> Each time the energy returned to the primary, some was lost as heat in the spark.<ref name="Huurdeman3"/><ref name="Beauchamp3"/> In addition, unless the coupling was very loose the oscillations caused the transmitter to transmit on two separate frequencies.<ref name="Beauchamp3"/><ref name="Burns2"/> Since the narrow passband of the receiver's resonant circuit could only be tuned to one of these frequencies, the power radiated at the other frequency was wasted.

This troublesome backflow of energy to the primary circuit could be prevented by extinguishing (quenching) the spark at the right instant, after all the energy from the capacitors was transferred to the antenna circuit.<ref name="Leggett2">[https://archive.org/details/wirelesstelegra00legggoog/page/n76 <!-- pg=55 --> Bernard Leggett (1921) ''Wireless Telegraphy, with special reference to the quenched-spark system'', p. 55-59]</ref><ref name="Burns2">{{cite book
| last1= Burns
| first1= Russell W.
| title= Communications: An International History of the Formative Years
| publisher= Institute of Electrical Engineers
| date= 2004
| pages= 361–362
| url= https://books.google.com/books?id=7eUUy8-VvwoC&q=quenched&pg=PA361
| isbn= 978-0863413278
}}</ref> Inventors tried various methods to accomplish this, such as air blasts and [[Elihu Thomson]]'s [[magnetic blowout]].<ref name="Beauchamp3"/><ref name="Burns2"/>

In 1906, a new type of spark gap was developed by German physicist [[Max Wien]],<ref name="Bard">{{cite book
| last1= Bard
| first1= Allen J.
| last2= Inzelt
| first2= György
| last3= Scholz
| first3= Fritz
| title= Electrochemical Dictionary
| edition= 2nd
| publisher= Springer Science and Business Media
| date= 2012
| pages= 972
| url= https://books.google.com/books?id=4TBWg3dIyKQC&q=max+wien&pg=PA972
| isbn= 978-3642295515
}}</ref> called the ''series'' or ''quenched'' gap.<ref name="Stanley1">{{cite book
| last1= Rupert
| first1= Stanley
| title= Text-book on Wireless Telegraphy, Vol. 1: General Theory and Practice
| publisher= Longmans Green and Co.
| date= 1919
| location= London
| pages= 200–204
| url= https://books.google.com/books?id=b4tCAQAAMAAJ&q=quenched+spark+singing&pg=PA200
}}</ref><ref name="Beauchamp2">{{cite book
| last1= Beauchamp
| first1= Ken
| title= History of Telegraphy
| publisher= IET
| date= 2001
| pages= 194–197
| url= https://books.google.com/books?id=k3XCkncd83AC&pg=PA193
| isbn= 978-0852967928
}}</ref><ref name="Leggett3">[https://archive.org/details/wirelesstelegra00legggoog/page/n81 <!-- pg=60 --> Bernard Leggett (1921) ''Wireless Telegraphy, with special reference to the quenched-spark system'', p. 60-63]</ref><ref name="Huurdeman3"/> A quenched gap consisted of a stack of wide cylindrical electrodes separated by thin insulating spacer rings to create many narrow spark gaps in series,<ref name="Beauchamp2"/> of around {{convert|0.1|-|0.3|mm|inch|sigfig=1|abbr=on}}.<ref name="Stanley1"/> The wide surface area of the electrodes terminated the ionization in the gap quickly by cooling it after the current stopped. In the inductively coupled transmitter, the narrow gaps extinguished ("quenched") the spark at the first nodal point (<span style="color:red;">Q</span>) when the primary current momentarily went to zero after all the energy had been transferred to the secondary winding ''(see lower graph)''.<ref name="Leggett2"/> Since without the spark no current could flow in the primary circuit, this effectively uncoupled the secondary from the primary circuit, allowing the secondary resonant circuit and antenna to oscillate completely free of the primary circuit after that (until the next spark). This produced output power centered on a single frequency instead of two frequencies. It also eliminated most of the energy loss in the spark, producing very lightly damped, long "ringing" waves, with decrements of only 0.08 to 0.25<ref name="Arco">{{cite journal
| last1= von Arco
| first1= Georg
| title= The New Telefunken Telegraph: A combination of the arc and spark systems
| journal= Scientific American Supplement
| volume= 67
| issue= 1746
| pages= 390
| date= 19 June 1909
| url= https://books.google.com/books?id=FgYiAQAAMAAJ&q=Max+wein+%22quenched+arc%22+damping&pg=PA390
| doi =10.1038/scientificamerican06191909-390supp
| access-date= 5 December 2018| url-access= subscription
}}</ref> (a Q of 12-38) and consequently a very "pure", narrow bandwidth radio signal. Another advantage was the rapid quenching allowed the time between sparks to be reduced, allowing higher spark rates of around 1000&nbsp;Hz to be used, which had a musical tone in the receiver which penetrated radio static better. The quenched gap transmitter was called the "singing spark" system.<ref name="Arco"/><ref name="Stanley1"/>

The German wireless giant [[Telefunken]] Co., Marconi's rival, acquired the patent rights and used the quenched spark gap in their transmitters.<ref name="Leggett3"/><ref name="Stanley1"/><ref name="Huurdeman3"/>
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