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Crystal radio

This article is about unpowered radio receivers. For crystal-controlled oscillators (as used in radios), see Crystal oscillator.
"Crystal set" redirects here. For the Australian rock band, see The Crystal Set.
Swedish crystal radio from 1922 made by Radiola, with earphones. The device at top is the radio's cat's whisker detector. A second pair of earphone jacks is provided.
1970s-era Arrow crystal radio marketed to children. The earphone is on left. The antenna wire, right, has a clip to attach to metal objects such as a bedspring, which serve as an additional antenna to improve reception.

A crystal radio receiver, also called a crystal set, is a simple radio receiver, popular in the early days of radio. It uses only the power of the received radio signal to produce sound, needing no external power. It is named for its most important component, a crystal detector, originally made from a piece of crystalline mineral such as galena.[1] This component is now called a diode.

Crystal radios are the simplest type of radio receiver[2] and can be made with a few inexpensive parts, such as a wire for an antenna, a coil of wire, a capacitor, a crystal detector, and earphones (because a crystal set has insufficient power for a loudspeaker).[3] However they are passive receivers, while other radios use an amplifier powered by current from a battery or wall outlet to make the radio signal louder. Thus, crystal sets produce rather weak sound and must be listened to with sensitive earphones, and can receive stations only within a limited range of the transmitter.[4]

The rectifying property of a contact between a mineral and a metal was discovered in 1874 by Karl Ferdinand Braun.[5][6][7] Crystals were first used as a detector of radio waves in 1894 by Jagadish Chandra Bose,[8][9] in his microwave optics experiments. They were first used as a demodulator for radio communication reception in 1902 by G. W. Pickard.[10] Crystal radios were the first widely used type of radio receiver,[11] and the main type used during the wireless telegraphy era.[12] Sold and homemade by the millions, the inexpensive and reliable crystal radio was a major driving force in the introduction of radio to the public, contributing to the development of radio as an entertainment medium with the beginning of radio broadcasting around 1920.[13]

Around 1920, crystal sets were superseded by the first amplifying receivers, which used vacuum tubes. With this technological advance, crystal sets became obsolete for commercial use[11] but continued to be built by hobbyists, youth groups, and the Boy Scouts[14] mainly as a way of learning about the technology of radio. They are still sold as educational devices, and there are groups of enthusiasts devoted to their construction.[15][16][17][18][19]

Crystal radios receive amplitude modulated (AM) signals, although FM designs have been built.[20][21] They can be designed to receive almost any radio frequency band, but most receive the AM broadcast band.[22] A few receive shortwave bands, but strong signals are required. The first crystal sets received wireless telegraphy signals broadcast by spark-gap transmitters at frequencies as low as 20 kHz.[23][24]

  1. ^ Carr, Joseph J. (1990). Old Time Radios! Restoration and Repair. US: McGraw-Hill Professional. pp. 7–9. ISBN 0-8306-3342-1.
  2. ^ Petruzellis, Thomas (2007). 22 Radio and Receiver Projects for the Evil Genius. US: McGraw-Hill Professional. pp. 40, 44. ISBN 978-0-07-148929-4.
  3. ^ Field, Simon Quellen (2003). Gonzo gizmos: Projects and devices to channel your inner geek. US: Chicago Review Press. p. 85. ISBN 978-1-55652-520-9.
  4. ^ Schaeffer, Derek K.; Thomas H. Lee (1999). The Design and Implementation of Low Power CMOS Receivers. Springer. pp. 3–4. ISBN 0-7923-8518-7.
  5. ^ Braun, Ernest; Stuart MacDonald (1982). Revolution in Miniature: The history and impact of semiconductor electronics, 2nd Ed. UK: Cambridge Univ. Press. pp. 11–12. ISBN 978-0-521-28903-0.
  6. ^ Riordan, Michael; Lillian Hoddeson (1988). Crystal fire: the invention of the transistor and the birth of the information age. US: W. W. Norton & Company. pp. 19–21. ISBN 0-393-31851-6.
  7. ^ Sarkar, Tapan K. (2006). History of wireless. US: John Wiley and Sons. p. 333. ISBN 0-471-71814-9.
  8. ^ Bose was first to use crystals for electromagnetic wave detection, using galena detectors to receive microwaves starting around 1894 and receiving a patent in 1904 Emerson, D. T. (Dec 1997). "The work of Jagadis Chandra Bose: 100 years of millimeter-wave research". IEEE Transactions on Microwave Theory and Techniques. 45 (12): 2267–2273. Bibcode:1997ITMTT..45.2267E. doi:10.1109/22.643830. ISBN 9780986488511. Retrieved 2010-01-19.
  9. ^ Sarkar (2006) History of wireless, pp. 94, 291–308
  10. ^ Douglas, Alan (April 1981). "The crystal detector". IEEE Spectrum. New York: Inst. of Electrical and Electronic Engineers: 64. doi:10.1109/MSPEC.1981.6369482. hdl:10366/158938. S2CID 44288637. Retrieved 2010-03-14. on Stay Tuned website
  11. ^ a b Basalla, George (1988). The Evolution of Technology. UK: Cambridge University Press. p. 44. ISBN 0-521-29681-1.
  12. ^ crystal detectors were used in receivers in greater numbers than any other type of detector after about 1907. Marriott, Robert H. (September 17, 1915). "United States Radio Development". Proc. of the Inst. Of Radio Engineers. 5 (3). US: Institute of Radio Engineers: 184. doi:10.1109/jrproc.1917.217311. S2CID 51644366. Retrieved 2010-01-19.
  13. ^ Corbin, Alfred (2006). The Third Element: A Brief History of Electronics. AuthorHouse. pp. 44–45. ISBN 1-4208-9084-0.
  14. ^ Kent, Herb; David Smallwood; Richard M. Daley (2009). The Cool Gent: The Nine Lives of Radio Legend Herb Kent. US: Chicago Review Press. pp. 13–14. ISBN 978-1-55652-774-6.
  15. ^ Jack Bryant (2009) Birmingham Crystal Radio Group, Birmingham, Alabama, US. Retrieved 2010-01-18.
  16. ^ The Xtal Set Society Archived 2006-01-14 at the Wayback Machine midnightscience.com . Retrieved 2010-01-18.
  17. ^ Darryl Boyd (2006) Stay Tuned Crystal Radio website. Retrieved 2010-01-18.
  18. ^ Al Klase Crystal Radios, Klase's SkyWaves website . Retrieved 2010-01-18.
  19. ^ Mike Tuggle (2003) Designing a DX crystal set Archived 2010-01-24 at the Wayback Machine Antique Wireless Association Archived 2010-05-23 at the Wayback Machine journal. Retrieved 2010-01-18.
  20. ^ Solomon, Larry J. (2007-12-30). "FM Crystal Radios". Archived from the original on 2007-12-30. Retrieved 2022-02-20.
  21. ^ Petruzellis, Thomas (2007). 22 Radio and Receiver Projects for the Evil Genius. US: McGraw-Hill Professional. p. 39. ISBN 978-0-07-148929-4.
  22. ^ Williams, Lyle R. (2006). The New Radio Receiver Building Handbook. The Alternative Electronics Press. pp. 20–23. ISBN 978-1-84728-526-3.
  23. ^ Lescarboura, Austin C. (1922). Radio for Everybody. New York: Scientific American Publishing Co. pp. 4, 110, 268.
  24. ^ Long distance transoceanic stations of the era used wavelengths of 10,000 to 20,000 meters, correstponding to frequencies of 15 to 30 kHz.Morecroft, John H.; A. Pinto; Walter A. Curry (1921). Principles of Radio Communication. New York: John Wiley & Sons. p. 187.
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