Guide to the Greenleaf Pickard Notebooks and Nikola Tesla Patents

Arrangement

Biographical / Historical

Dr. Greenleaf Whittier Pickard was born February 14, 1877, in Portland, Maine and died on January 8, 1956 in Newton, Massachusetts. Dr. Pickard was a grandnephew of the poet John Greenleaf Whittier, and was a graduate of Harvard University and the Massachusetts Institute of Technology. In 1899 he received a grant from the Smithsonian Institution to support his wireless research at Blue Hill Observatory in Milton, Massachusetts. He was an engineer at the American Telephone and Telegraph Company (1902-1906); and after 1945 he was head of Pickard and Burnes, an electronics engineering firm.

Pickard discovered that a number of naturally occurring crystalline minerals could detect radio signals. The contact between a fine metallic wire (cat's whisker) and the surface of certain crystalline materials rectifies and demodulates high frequency alternating currents, such as those produced in a receiving antenna by radio waves. Pickard patented a crystal detector in 1906. The point-contact rectifier was the forerunner of the transistor invented in 1948. Pickard conducted experiments to determine the effect of sun and sunspots, meteor showers, atmosphere pressure and temperature on reception. He contributed to the development of the direction finder, and noted in 1908 that errors in reading radio compasses might be caused by buildings, trees, and other objects.