Magic eye tube
A vacuum tube that visually indicates signal strength for tuning.
Last updated
A cathode ray tube tuning indicator, the magic eye tube, was created to offer a less expensive option compared to needle-based meters.[1] Vacuum tube receivers incorporated these tuning indicators from approximately 1936 until 1980, after which transistors superseded vacuum tubes in radios.[1]
Quick Facts
- Inventor
- Allen B. DuMont
- Year of invention
- 1932
- First commercial tube
- RCA 6E5
- Period of use
- around 1936 to 1980
Facts from the source article.
Key facts and history
The magic eye arrived in 1935 and began to replace earlier tuning methods like meters, shadow meters, and neon indicators.[2] Earlier tuning aids included separate voltmeters and milliamp-meters on a Ducretet radio from 1923/24.[2] Signal sources for early indicators were anode current from RF tubes, screen grid current, or rectified current from the second detector.[2] The magic eye had to be adapted for new demands like double action for weak and strong stations, FM, and stereo.[2]
The magic eye was replaced by solid state techniques such as LEDs and LCDs.[2] Allen B. DuMont invented the magic eye tube in 1932, and during the 1930s he focused on extending the operational life of cathode ray tubes.[3] The initial magic eye tube offered for sale was the RCA 6E5, which debuted in 1935.[4]
What the cited sources add
RCA followed the 6E5 with a 6G5 registered February 21, 1936, and later introduced the 2E5 and 2G5 for sets with 2.5 volt filaments.[5] The Radio Museum entry for the Tuneon describes a neon-filled three-electrode tuning indicator used before the magic eye.[6] The Tuneon record also lists other early tuning indicator systems such as the Viso-Glo, Tune-A-Lite, Flash-O-Graph, and Shadowgraph.[6]
References
- Wikipedia, "Magic eye tube" (CC BY-SA 4.0), which cites: "Precise dB Monitoring With Eye Tubes"; Erb, "History of tuning indicators; meters, graphs, Magic Eye, LED", Radio History forum, 2009-07-27; Erb, "History of tuning indicators; meters, graphs, Magic Eye, LED", Radio History forum, 2009-07-27; Radio Museum: Tuneon (we also read that source) en.wikipedia.org
- Erb, "History of tuning indicators; meters, graphs, Magic Eye, LED", Radio History forum, 2009-07-27. facts only, no text reused. radiomuseum.org
- Wikipedia, "Magic eye tube" (CC BY-SA 4.0), which cites: "Cathode ray device"; "Cathode ray tube"; David Weinstein, The Forgotten Network: DuMont and the Birth of American Television. Temple University Press, 2006, p.11 (original not read by us) en.wikipedia.org
- Wikipedia, "Magic eye tube" (CC BY-SA 4.0), which cites: "Tuning indicator tube"; Radio Museum: 6E5 (we also read that source) en.wikipedia.org
- Radio Museum: 6E5. facts only, no text reused. radiomuseum.org
- Radio Museum: Tuneon. facts only, no text reused. radiomuseum.org
Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Magic eye tube (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Magic eye tube (CC BY-SA 4.0).
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