Greenleaf Whittier Pickard (February 14, 1877 – January 8, 1956) was an American

electrical engineer Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems that use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...

and inventor. He was largely responsible and most famous for the development of the

crystal detector A crystal detector is an obsolete electronic component used in some early 20th century radio receivers. It consists of a piece of crystalline mineral that rectifies an alternating current radio signal. It was employed as a detector ( demod ...

, the earliest type of diode detector, although he was not the earliest discoverer of the

rectifying A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as ''rectification'', since it "straightens" t ...

properties of contact between certain solid materials.G. W. Pickard, "How I Invented the Crystal Detector". ''Electrical Experimenter'', vol. VII, no. 4, p. 325, Aug. 1919
/ref> The crystal detector was the central component in many early

radio receiver In radio communications, a radio receiver, also known as a receiver, a wireless, or simply a radio, is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. ...

s from around 1906 until about 1920. Pickard also experimented with

antennas In radio-frequency engineering, an antenna (American English) or aerial (British English) is an electronic device that converts an alternating electric current into radio waves (transmitting), or radio waves into an electric current (receivi ...

radio wave Radio waves (formerly called Hertzian waves) are a type of electromagnetic radiation with the lowest frequencies and the longest wavelengths in the electromagnetic spectrum, typically with frequencies below 300 gigahertz (GHz) and wavelengths g ...

propagation and noise suppression. On August 30, 1906 he filed a patent for a

silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

detector, which was granted on November 20, 1906. On June 10, 1907 he filed a patent for a "Magnetic Aerial" (a loop aerial) which was granted on January 21, 1908. Pickard's loop antenna had directional properties that could be used to reduce interference to the intended wireless communications. On June 21, 1911 he filed a patent on a crystal detector incorporating a springy low inertia wire of about 24

gauge Gauge ( ) may refer to: Measurement * Gauge (instrument), any of a variety of measuring instruments * Gauge (firearms) * Wire gauge, a measure of the size of a wire ** American wire gauge, a common measure of nonferrous wire diameter, especia ...

formed with a loop or helix and pointed to make contact with the crystal. Crystal detectors incorporating this construction would become the most widely used and popularly known by the term ''cat whisker detector''. This patent was granted on July 21, 1914. Greenleaf Whittier Pickard was named after his great-uncle, the American Quaker

John Greenleaf Whittier John Greenleaf Whittier (December 17, 1807 – September 7, 1892) was an American Quaker poet and advocate of the abolition of slavery in the United States. Frequently listed as one of the fireside poets, he was influenced by the Scottish poet ...

(1807-1892). He was the grandson of author and humorist Mathew Franklin Whittier. Pickard was president of the

Institute of Radio Engineers The Institute of Radio Engineers (IRE) was a professional organization which existed from 1912 until December 31, 1962. On January 1, 1963, it merged with the American Institute of Electrical Engineers (AIEE) to form the Institute of Electrical ...

in 1913.

Patents

* - ''Electrostatic separation'' * - ''Electrostatic separation'' * - ''Electrostatic separation'' * - ''Electrostatic separation'' * - ''Means for receiving intelligence communicated by electric waves'' (silicon detector), 1906 * - ''Electrostatic separator'', 1907 * - ''Means for receiving intelligence communicated by electric waves'' (

copper sulfate Copper sulfate may refer to: * Copper(II) sulfate, CuSO4, a common, greenish blue compound used as a fungicide and herbicide * Copper(I) sulfate, Cu2SO4, an unstable white solid which is uncommonly used {{chemistry index Copper compounds ...

solution detector), 1907 * - ''Intelligence intercommunication by magnetic wave component'' (loop antenna), 1908 * - ''Means for receiving intelligence communicated by electric waves'' (spring-loaded detector contact), 1908 * - ''Oscillation receiver'' (fused zinc oxide detector), 1908 * - ''Oscillation receiver'' (polished silicon detector, 1908 * - ''Oscillation detecting means'' (

molybdenite Molybdenite is a mineral of molybdenum disulfide, Mo S2. Similar in appearance and feel to graphite, molybdenite has a lubricating effect that is a consequence of its layered structure. The atomic structure consists of a sheet of molybdenum at ...

detector), 1908 * - ''Oscillation detector and rectifier'' ("plated"

silicon carbide Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing silicon and carbon. A wide bandgap semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder a ...

detector with DC bias), G.W. Pickard, 1909 * - ''Oscillation receiver'' (fractured surface red zinc oxide ( zincite) detector), 1909 * - ''Oscillation device'' (iron pyrite detector), 1909 * - ''Electrical Space Communication'' (interference mitigation), 1909 * - ''Telephone receiving apparatus'' (protective piece and adjustable diaphragm distance), 1910 * - ''Detector for wireless telegraphy and telephony'' (looped or humped springy wire detector contact), 1914 * - ''Oscillation detectors'' (pairs of minerals), 1914 * - ''Valve detector for wireless'' (vacuum tube with conducting shield to drain static), 1915 * - ''Receiver for wireless telephony and telegraphy'' (interrupted or switched circuit instead of rectifier), 1916 * - ''Means for receiving intelligence communicated by electric waves'' (receiving circuit, divided from #836531), 1917 * - ''Optical selection of split mica sheets'' * - ''Distinguishing dielectric sheets'' * - ''Electrical reactance and method and apparatus'' * - ''Radio Receiving Apparatus'' (multiple loop antennas), 1920 * - ''Extreme loading condenser'' ''Reissued'' * - ''Means for receiving intelligence communicated by electric waves''

References

;Citations {{DEFAULTSORT:Pickard, Greenleaf Whittier Radio pioneers American inventors IEEE Medal of Honor recipients People from Portland, Maine 1877 births 1956 deaths