Precision cat's whisker detector



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English: A cat's whisker detector, an antique radio component used in early crystal radios, from a 1914 book on wireless telegraphy. This was a precision micrometer type. The vertical needle on the right gently touches the face of a crystal of iron pyrite (Fool's gold) contained in the cylindrical metal capsule below it, forming a diode which is used to rectify the received radio signal. Only certain sites on the crystal's face functioned as rectifying junctions, so the device had to be adjusted by trial and error to find a "sweet spot" before each use. The crude device was very sensitive to the contact between needle and crystal, so the spring loaded micrometer screw on the left can be used to adjust the pressure precisely.
Date 1914(1914)
Source Downloaded 2009-11-08 from Alfred Powell Morgan (1914) Wireless Telegraph Construction for Amateurs, 3rd Ed., p. 134, fig. 106 on Google Books
Author Alfred Powell Morgan
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Public domain in USA - published in USA prior to 1923


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