File:Carborundum detector & bias battery 1928.jpg
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Carborundum_detector_&_bias_battery_1928.jpg (327 × 350 pixels, file size: 27 KB, MIME type: image/jpeg)
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[edit]DescriptionCarborundum detector & bias battery 1928.jpg |
English: A carborundum crystal detector used in early vacuum tube radio receivers, from a 1928 radio magazine. An early semiconductor diode, its function was to rectify the radio signal, extracting the audio (sound) signal from the radio frequency carrier wave. Crystal detectors, first used in unpowered crystal radios in the first decades of the 20th century, were also used in early vacuum tube radios during the 1920s because they were more sensitive than the triode grid leak detectors also used. The detector, inside the cartridge at top, consisted of a piece of carborundum (silicon carbide) with a spring-loaded contact pressing against it. Carborundum was used because it did not require the delicate "cat's whisker" wire contact that other crystal detectors such as galena did, so it did not require adjustment and could be mounted in a sealed cartridge. The carborundum diode had a wide band gap and required a DC bias voltage of several volts across it to reach full sensitivity. This module consists of the diode (top), a bias battery (bottom), and a potentiometer (variable resistor) (center), to adjust the bias. It was mounted on the front panel of the receiver and the potentiometer was adjusted until the radio station was heard loudest from the speaker. |
Date | |
Source | Retrieved July 19, 2014 from Radio News magazine, Experimenter Publishing Co., New York, Vol. 9, No. 8, February 1928, p. 941 on http://www.americanradiohistory.com |
Author | Unknown authorUnknown author |
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This image is from an advertisement without a copyright notice published in a 1928 US magazine. In the United States, advertisements published in collective works (magazines and newspapers) are not covered by the copyright notice for the entire collective work. (See U.S. Copyright Office Circular 3, "Copyright Notice", page 3, "Contributions to Collective Works".) Since the advertisement was published before 1978 without a copyright notice, it falls into the public domain. |
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This work is in the public domain in the United States because it was published in the United States between 1929 and 1977, inclusive, without a copyright notice. For further explanation, see Commons:Hirtle chart as well as a detailed definition of "publication" for public art.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties. العربية ∙ беларуская (тарашкевіца) ∙ čeština ∙ Deutsch ∙ Ελληνικά ∙ English ∙ español ∙ français ∙ Bahasa Indonesia ∙ italiano ∙ 日本語 ∙ 한국어 ∙ македонски ∙ Nederlands ∙ português ∙ русский ∙ sicilianu ∙ slovenščina ∙ ไทย ∙ Tiếng Việt ∙ 中文(简体) ∙ 中文(繁體) ∙ +/− |
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current | 08:27, 30 October 2015 | ![]() | 327 × 350 (27 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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