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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.
Foxhole radios consisted of a wire aerial, a coil of wire serving as inductor, headphones, and some sort of improvised diode detector to rectify the signal. Detectors consisted of an electrical contact between two different conductors with a semiconducting film of corrosion between them. They were devised from various common objects.
The most common type was the so-called cat's whisker detector, which consisted of a piece of crystalline mineral, usually galena (lead sulfide), with a fine wire touching its surface. [1] [4] [5] The "asymmetric conduction" of electric current across electrical contacts between a crystal and a metal was discovered in 1874 by Karl Ferdinand ...
Recreation of the 1907 experiment by H. J. Round on the observation of electroluminescence from a point contact with a carborundum (silicon carbide) crystalIn some later experiments with cat's whisker detectors using a variety of substances, he passed current through them and noticed that some gave off light – the first known report of the effect of the light-emitting diode (LED).
Greenleaf Whittier Pickard (February 14, 1877 – January 8, 1956) was an American electrical engineer and inventor. He was largely responsible and most famous for the development of the crystal detector, the earliest type of diode detector, although he was not the earliest discoverer of the rectifying properties of contact between certain solid materials. [1]
Prior to the introduction of the Audion, radio receivers had used a variety of detectors including coherers, barretters, and crystal detectors. The most popular crystal detector consisted of a small piece of galena crystal probed by a fine wire commonly referred to as a "cat's-whisker detector". They were very unreliable, requiring frequent ...
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Both natural and synthetic zincite crystals are significant for their early use as semiconductor crystal detectors in the early development of crystal radios before the advent of vacuum tubes. As an early radio detector it was used in conjunction with another mineral, galena, and this device was known as the cat's-whisker detector.