Crystal sets represented an inexpensive and technologically simple method of receiving these signals at a time when the embryonic radio broadcasting industry was beginning to grow. This device brought radiotelephones and voice broadcast to a public audience. Another benefit of crystals was that they could demodulate amplitude modulated signals. Several other minerals also performed well as detectors. The most common crystal used is a small piece of galena pyrite was also often used, as it was a more easily adjusted and stable mineral, and quite sufficient for urban signal strengths. Ī crystal detector includes a crystal, usually a thin wire or metal probe that contacts the crystal, and the stand or enclosure that holds those components in place. On August 30, 1906, Greenleaf Whittier Pickard filed a patent for a silicon crystal detector, which was granted on November 20, 1906. patent for "A Device for Detecting Electrical Disturbances" that mentioned the use of a galena crystal this was granted in 1904, #755840. Indian physicist Jagadish Chandra Bose was first to use a crystal as a radio wave detector, using galena detectors to receive microwaves starting around 1894. In the early 20th century, various researchers discovered that certain metallic minerals, such as galena, could be used to detect radio signals. These, however, lacked the sensitivity to detect weak signals. The coherer was the first means of detecting a radio signal. Ĭrystal radio (1915) kept at the Museum of the radio - Monteceneri (Switzerland)Įarly radio telegraphy used spark gap and arc transmitters as well as high-frequency alternators running at radio frequencies. The first crystal sets received wireless telegraphy signals broadcast by spark-gap transmitters at frequencies as low as 20 kHz. A few receive shortwave bands, but strong signals are required. They can be designed to receive almost any radio frequency band, but most receive the AM broadcast band. Ĭrystal radios receive amplitude modulated (AM) signals, although FM designs have been built. They are still sold as educational devices, and there are groups of enthusiasts devoted to their construction. With this technological advance, crystal sets became obsolete for commercial use but continued to be built by hobbyists, youth groups, and the Boy Scouts mainly as a way of learning about the technology of radio. Īround 1920, crystal sets were superseded by the first amplifying receivers, which used vacuum tubes. 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. Crystal radios were the first widely used type of radio receiver, and the main type used during the wireless telegraphy era. They were first used as a demodulator for radio communication reception in 1902 by G. Crystals were first used as a detector of radio waves in 1894 by Jagadish Chandra Bose, in his microwave optics experiments. The rectifying property of a contact between a mineral and a metal was discovered in 1874 by Karl Ferdinand Braun. 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. 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. This component is now called a diode.Ĭrystal radios are the simplest type of radio receiver 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). It is named for its most important component, a crystal detector, originally made from a piece of crystalline mineral such as galena. It uses only the power of the received radio signal to produce sound, needing no external power. 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.Ī crystal radio receiver, also called a crystal set, is a simple radio receiver, popular in the early days of radio. 1970s-era Arrow crystal radio marketed to children.
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