File:Marconi parabolic shortwave antenna 1922 Hendon, UK.png

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Marconi_parabolic_shortwave_antenna_1922_Hendon,_UK.png ‎(641 × 423 pixels, file size: 76 KB, MIME type: image/png)

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Summary

Description
English: Experimental wire parabolic antenna built by radio entrepreneur Guglielmo Marconi at Hendon, UK, to investigate transatlantic beam shortwave transmission. It consists of a vertical half-wave monopole feed antenna consisting of a hanging wire at the focus of a parabolic reflector consisting of a curtain of hanging vertical wires suspended from the towers by horizontal cables. It was driven at 15 meters (20 MHz) by a 700 watt vacuum tube transmitter. Alterations to image: increased contrast and used sharpening filter in Gimp to bring out wires against sky
Date
Source Retrieved 21 June 2020 from Frank Parker Stockbridge, "Marconi tells what radio needs" in Popular Science magazine", Popular Science Publishing Co., New York, NY, Vol. 112, No.1, January 1928, p. 32 on Google Books
Author Frank Parker Stockbridge
Permission
(Reusing this file)		 This 1928 issue of Popular Science magazine would have the copyright renewed in 1956. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. Search of the Renewals for Periodicals for 1955, 1956, and 1957 show no renewal entries for Popular Science. Therefore the copyright was not renewed and it is in the public domain.

Licensing

Public domain
This work is in the public domain because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the copyright was not renewed. For further explanation, see Commons:Hirtle chart and the copyright renewal logs.
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 (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.

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Parabolic antenna built by Guglielmo Marconi at Hendon UK 1922

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current02:47, 22 June 2020Thumbnail for version as of 02:47, 22 June 2020641 × 423 (76 KB)wikimediacommons>ChetvornoUploaded a work by Frank Parker Stockbridge from Retrieved 21 June 2020 from [https://books.google.com/books?id=fycDAAAAMBAJ&pg=PA32 Frank Parker Stockbridge, "Marconi tells - what radio needs" in ''Popular Science magazine", Vol. 112, No.1, January 1928, p. 32] on Google Books with UploadWizard

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