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Greenleaf Whittier Pickard : 1877 - 1956


In 1906 Greenleaf Whittier Pickard used a fused silicon detector, a year later he perfects the 'crystal' detector and takes out a patent for the use of silicon in detectors. In 1911 Pickard filed his 'cats whisker' detector patent


Source: Crystal Radio: History, Fundamentals and Design


Greenleaf Whittier Pickard, (b. Feb 14, 1877 d. 1956>. Engineer, invented the crystal detector (one of the first devices widely used for receiving radio broadcasts) and who was also one of the first scientists to demonstrate the wireless electromagnetic transmission of speech.


Source: http://interprep.com/datebook/date0108.htm


Greenleaf Whittier Pickard conducted numerous experiments to determine the effect of the sun and sunspots on radio. In his study of the polarisation of radio waves, he contributed to development of the direction finder, and noted as early as 1908 that errors in reading radio compasses might be caused by buildings, trees and other objects which flip flopped the waves or through reflection fooled the direction finder.

Linked with the name Pickard in crystal detector development was that of General H. C. Dunwoody of the United States Army, he [also?] observed that carborundum could be used as a detector. Pickard had more than 100 patents [to his name]. He became consulting engineer of the Yankee Network in 1934 specialising ultra high frequencies and radio frequency modulation more popularly known as FM.


Source: Loren Haroldson, Ellendale, MN, 56026, USA


The rectifying properties of crystals were discovered in 1912 by the American electrical engineer Greenleaf Whittier Pickard, who pointed out that crystals can be used as detectors. This discovery gave rise to the so-called crystal sets popular about 1920.


Source: http://www.penstock.avnet.com/radio.htm


Greenleaf Whittier Pickard (b. Feb. 14, 1877, Portland, Maine, U.S.--d. Jan. 8, 1956, Newton, Mass.), U.S. electrical engineer who invented the crystal detector (one of the first devices widely used for receiving radio broadcasts) and who was also one of the first scientists to demonstrate the wireless electromagnetic transmission of speech.

Pickard, who was a grandnephew of the poet John Greenleaf Whittier, was educated at Harvard University and the Massachusetts Institute of Technology, Cambridge. In 1899, at the Blue Hills Observatory in Milton, Mass., he transmitted spoken messages by radio over a distance of 10 miles, using a carbon-steel detector to recover the audible signal that had been impressed on the radio-frequency carrier waves.

As an engineer at the American Telephone and Telegraph Company (1902-06), he contributed to the development of the radiophone; from 1907 until 1930 he worked with the Wireless Specialty Apparatus Co., and after 1945 he headed the electronics engineering firm of Pickard and Burns.

Pickard is best known for discovering that the contact between a fine metallic wire ("cats whisker") and the surface of certain crystalline materials (notably silicon) rectifies and demodulates high-frequency alternating currents, such as those produced in a receiving antenna by radio waves.

This device, called a crystal detector and patented by Pickard in 1906, was an essential component of the crystal set, a form of radio receiver that was popular until the crystal detector was superseded by the triode vacuum tube. (The point-contact rectifier was the forerunner of the transistor, invented in 1948.)


Source: http://www.eb.com:180/cgi-bin/g?DocF=micro/466/71.html


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