Detectors 089
Detectors 089 : Particle Detectors: (4.3) Cat's-Whisker Detector: (4) History: Unlike modern radio stations that transmit sound, the radio transmitters during the first three decades of radio transmitted information by telegraphy, turning the transmitter on and off with a switch called a telegraph key to spell out messages in Morse code, consisting of "dots" and "dashes", so early radio receiving apparatus merely had to detect the presence or absence of the radio signal, not convert it into audio. The device that did this was called a detector. The crystal detector was the most successful of many detector devices that were used in the early days of radio. It replaced electrolytic, magnetic, and particularlycoherer detectors in radio receivers around 1906. Later, when AM radio transmission was developed to transmit sound, around World War I, crystal detectors proved able to receive this as well. The "unilateral conduction" of crystals, as it was then called, was discovered by Ferdinand Braun, a German physicist, in 1874 at the University of W?rzburg, before radio had been invented. Indian scientist Jagadish Chandra Bose was the first to use a crystal to detect radio waves, in his pioneering experiments with microwaves in 1894, applying for a patent on a galena detector in 1901. The cat's-whisker detector was developed as a practical device mainly by G. W. Pickard. His first detector, which used a silicon crystal, was patented in 1906. At nearly the same time, Henry Harrison Chase Dunwoody, a retired general in the U. S. Army Signal Corps, patented the silicon carbide (carborundum) detector, an artificial substance created accidentally during attempts by Edward Acheson to create diamonds. Pickard tested more than 30,000 combinations of crystal and wire contacts and developed several types of detectors that saw wide use. One variation consisted of a pair of different crystals with their faces touching, such as zincite touching bornite or chalcopyrite. Pickard named this the Perikon detector, from "PERfect pIcKard cONtact". Other detectors patented by Pickard included the common crystal iron pyrite
No records Found