Editing Spark-gap transmitter (section)

==== Marconi's timed spark system ====
In 1912 in his high-power stations Marconi developed a refinement of the rotary discharger called the "timed spark" system, which generated what was probably the nearest to a [[continuous wave]] that sparks could produce.<ref name="Bucher2">{{cite book
| last1= Bucher
| first1= Elmer E.
| title= Practical Wireless Telegraphy
| publisher= Wireless Press, Inc.
| date= 1917
| location= New York
| pages= 274–275
| url= https://archive.org/stream/wirelesstele00buchrich#page/274/mode/2up
}}</ref><ref name="Coursey">{{cite journal
| last1= Coursey
| first1= Phillip R.
| title= The Marconi Timed-Spark Continuous-Wave Transmitter
| journal= Wireless World
| volume= 7
| issue= 78
| pages= 310–316
| date= September 1919
| url= https://www.americanradiohistory.com/Archive-Wireless-World/10s/Wireless-World-1919-09.pdf
| access-date= 19 August 2018}}</ref><ref name="Sarkar" />{{rp|p.399}} He used several identical resonant circuits in parallel, with the capacitors charged by a DC [[dynamo]].<ref name="Goldsmith">{{cite book
| last1= Goldsmith
| first1= Alfred N.
| title= Radio Telephony
| publisher= Wireless Press, Inc.
| date= 1918
| location= New York
| pages= 73–75
| url= https://archive.org/stream/radiotelephony00goldgoog#page/n86/mode/2up
}}</ref> These were discharged sequentially by multiple rotary discharger wheels on the same shaft to create overlapping damped waves shifted progressively in time, which were added together in the oscillation transformer so the output was a [[superposition principle|superposition]] of damped waves. The speed of the discharger wheel was controlled so that the time between sparks was equal to an integer multiple of the wave period. Therefore, oscillations of the successive wave trains were [[in phase]] and reinforced each other. The result was essentially a continuous sinusoidal wave, whose amplitude varied with a ripple at the spark rate. This system was necessary to give Marconi's transoceanic stations a narrow enough bandwidth that they didn't interfere with other transmitters on the narrow [[very low frequency|VLF]] band. Timed spark transmitters achieved the longest transmission range of any spark transmitters, but these behemoths represented the end of spark technology.<ref name="Sarkar" />{{rp|p.399}}

{{multiple image
| align= center
| direction= horizontal
| header =
| image1= Marconi transatlantic wireless station at Carnarvon, Wales 1917.jpg
| width1= 302
| caption1= Transmitter building, showing the 36 feedlines feeding power to the 3,600 ft. flattop wire antenna.
| image2= Marconi Carnarvon 300kW transatlantic spark transmitter 1919 - tuning coil.png
| width2= 235
| caption2= 5 ft diameter primary coil of oscillation transformer, consisting of 3 turns of specialized [[litz wire]] one foot thick
| image3= Marconi Carnarvon 300kW transatlantic spark transmitter 1919 - rotary spark dischargers.png
| width3= 260
| caption3= The three 5 ft rotary spark discharger wheels of the "timed spark" system.
| footer= Marconi 300&nbsp;kW transatlantic timed spark transmitter built 1916 at [[Caernarfon|Carnarvon]], [[Wales]], one of the most powerful spark transmitters ever built. During World War I it transmitted telegram traffic at 200 words per minute on 21.5&nbsp;kHz to receivers in Belmar, New Jersey.<ref name="WirelessWorld">{{cite journal
| title= Great Wireless Stations: Carnarvon
| journal= Wireless World
| volume= 7
| issue= 78
| pages= 301–307
| date= September 1919
| url= https://www.americanradiohistory.com/Archive-Wireless-World/10s/Wireless-World-1919-09.pdf
| access-date= 19 August 2018}}</ref> The roar of the spark could reportedly be heard a kilometer away. On 22 September 1918 it transmitted the first wireless message from Britain to Australia, a distance of 15,200&nbsp;km (9,439&nbsp;miles).<ref name="MacKinnon">{{cite web
| last= MacKinnon
| first= Colin
| title= The first direct wireless messages from England to Australia
| work= Australian Amateur Radio History
| publisher= VK2DYM's military radio and radar information site
| date= 2004
| url= https://www.qsl.net/vk2dym/radio/Marconi.htm
| access-date= 4 May 2018}}</ref> In 1921 it was replaced by [[Alexanderson alternator]] transmitters.
}}