Greenleaf Whittier Pickard (February 14, 1877, Portland, Maine– January 8, 1956, Newton, Massachusetts) was a United States radio pioneer. Pickard was a researcher in the early days of wireless. While not the earliest discoverer of the rectifying properties of contact between certain solid materials, he was largely responsible and most famous for the development of the crystal detector, the earliest type of diode detector. The crystal detector was the central component in many early radio receivers from around 1906 until about 1920. Pickard also experimented with antennas, radio wave propagation and noise suppression.On August 30, 1906 he filed a patent for a silicon crystal detector, which was granted on November 20, 1906.On June 10, 1907 he filed a patent for a Magnetic Aerial (a loop ae