File:Radiola AR-812 superheterodyne receiver.png
Radiola_AR-812_superheterodyne_receiver.png (737 × 304 pixels, file size: 62 KB, MIME type: image/png)
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Summary
[edit]DescriptionRadiola AR-812 superheterodyne receiver.png |
English: The RCA Radiola AR-812 radio receiver, the first consumer superheterodyne receiver. The superheterodyne circuit, invented by US inventor Edwin Armstrong in 1918 during World War 1 when he was working for the US Army Signal Corps, is the circuit used in the vast majority of radio receivers today. The rights were purchased by RCA, and the AR-812 medium wave receiver was released March 4, 1924. It used 6 UV-199 triodes: a mixer, a local oscillator, two IF and two audio amplifiers in a push-pull output stage, with an IF of 45 kHz, and was priced at $289 with tubes and horn speaker, and $220 without. It was built to be semi-portable, with compartments for the batteries in back and a handle on top, although it weighed 30 lbs. without batteries. The two large knobs are the input and local oscillator tuning, they had to be adjusted in tandem. They had blank carboard dials, so users could mark the positions of stations on them. The small knobs adjust the filament current. Its superior sensitivity and selectivity compared to competing receivers made it a commercial success. There are many reports of transcontinental and transoceanic reception. |
Date | |
Source | Retrieved July 6, 2014 from James Martin, 'The "How and Why" of Superhet Circuits' in Radio News magazine, Ziff-Davis Publishing Co., New York, Vol. 12, No. 5, November 1930, p. 396 on American Radio History site |
Author | James Martin |
Permission (Reusing this file) |
This 1930 issue of Radio News magazine would have the copyright renewed in 1958. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. [1] Search of the Renewals for Periodicals for 1957, 1958 and 1959 show no renewal entries for Radio News. Therefore the copyright was not renewed and it is in the public domain. |
Licensing
[edit]Public domainPublic domainfalsefalse |
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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File change date and time | 05:58, 7 July 2014 |