File:Radiola AR-812 superheterodyne ad.jpg
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Summary
| Description |
English: An advertisement for the RCA Radiola AR-812 radio, the first commercially produced superheterodyne radio receiver. The superheterodyne receiver circuit, used in virtually all modern radios, was invented by US engineer Edwin Armstrong in 1918 during World War 1. 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 amplifier stages, 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. In an apparent attempt to prevent competitors "reverse-engineering" it, the innards were encased in solid wax. Alterations to image: Cropped out advertising copy |
| Date | |
| Source | Retrieved February 19, 2014 from Motorboating, International Magazine Co., New York, Vol. 33, No. 5, May, 1924, p. 71 on Google Books |
| Author | Unknown author |
| Permission (Reusing this file) |
This 1924 issue of Motorboating magazine would have the copyright renewed in 1952. 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 1951, 1952 and 1953 show no renewal entries for Motorboating. Therefore the copyright on the magazine was not renewed and it is in the public domain. |
Licensing
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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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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 04:34, 20 February 2014 | | 1,218 × 881 (149 KB) | Chetvorno | User created page with UploadWizard |
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