File:Telefunken arc radiotelephone.jpg
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DescriptionTelefunken arc radiotelephone.jpg |
English: One of the first pre-vacuum tube AM radio transmitters, developed December 1906 by the German firm Telefunken (Gesellschaft für drahtlose Telegrafie). In experiments on December 14, 1906 it transmitted voice signals 36 km (24 mi) from Berlin to Nauen, Germany. Based on the Poulsen arc transmitter invented by William Duddell and Valdemar Poulsen in 1903, it used 6 short electric arcs between carbon an copper electrodes (inside vertical tubes) with 220 VDC applied, connected to a tuned circuit consisting of a coil and capacitor in series (located under the table) to make a continuous wave electronic oscillator. The negative resistance of the arcs excited radio frequency oscillations in the tuned circuit. The radio signal was modulated by the carbon microphone (cone, above) in the transmitter's antenna wire. The pressure of the sound waves varied the resistance of the carbon granules, which varied the current applied to the antenna. The small breadboard mounted on standoffs on the desk is the receiving apparatus. Due to lack of a magnetic blowout the efficiency was low. Arc transmitters like this were one of the first technologies that could transmit sound, but were only used for a short period until the early 1920s, when they were replaced by the vacuum tube invented by Lee De Forest in 1906. More information in Alfred N. Goldsmith, "Radio Telephony, Article 4" in Wireless Age magazine, April 1917, p. 472-476 |
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Source | Downloaded 21 September 2013 from Ernst Walter Rühmer 1908 Wireless Telephony in Theory and Practice, D. Van Nostrand Co., New York, translated by James Erskine-Murray, p. 171, fig. 127 on Google Books |
Author | Ernst Walter Rühmer |
Licensing edit
Public domainPublic domainfalsefalse |
This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See this page for further explanation.
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This image might not be in the public domain outside of the United States; this especially applies in the countries and areas that do not apply the rule of the shorter term for US works, such as Canada, Mainland China (not Hong Kong or Macao), Germany, Mexico, and Switzerland. The creator and year of publication are essential information and must be provided. See Wikipedia:Public domain and Wikipedia:Copyrights for more details.
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Annotations InfoField | This image is annotated: View the annotations at Commons |
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English: Six arcs in series between carbon and copper electrodes generate the radio frequency oscillations
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English: Crystal receiver
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English: Carbon microphone in antenna lead
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current | 10:55, 3 May 2021 | 1,095 × 2,135 (568 KB) | Materialscientist (talk | contribs) | FFT | |
19:29, 21 September 2013 | 1,095 × 2,135 (322 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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