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A quad antenna is a type of radio antenna frequently used by amateur radio operators. Like a Yagi-Uda antenna ("Yagi"), a quad consists of a driven element and parasitic elements; however in a quad, each of these elements takes the form of a loop, which may be square, round, or some other shape. == History == The quad antenna is a development of several inventions. In 1924, Moses Jacobson patented a loop antennas with rhombic shape.〔U.S. Patent 1747008, Antenna. http://www.google.com/patents/US1747008〕 In 1938, George Brown et al. patented a loop antenna with rhombic shape and quarterwave sides.〔U.S. Patent 2207781, Ultra high frequency antenna. http://www.google.com/patents/US2207781〕 In 1951 Clarence C. Moore, W9LZX, a Christian Missionary and engineer at HCJB (a shortwave missionary radio station high in the Andean Mountains) developed and patented 〔U.S. Patent 2537191. http://www.google.com/patents/US2537191〕a two-turn loop antenna that he called a "quad". He developed this antenna to resolve issues caused by large coronal discharges while using a beam antenna in the thin air of higher altitudes. This is not the antenna termed "quad" today. Moore describes his antenna as "a pulled-open folded dipole" and describes the time when it was developed: Moore's design eliminated interference from coronal discharge. "End effect", which is inherent with the Yagi, is absent in a quad because its elements have no ends. But other advantages appeared. The higher impedance mentioned in the quote above translates to lower current and thus lower loss on the transmission lines, and gain is higher than that of a Yagi. In 1957 James Sherriff McCaig patented what we now as a "cubical" (two-element) multi-band quad antenna.〔GB Patent 850974 Improvements relating to composite aerials. http://www.puertobalsillas.com/radio/GB850974A.pdf GB850974A〕 In 1960 Rudolf Baumgartner patented the Swiss quad〔Swiss Patent 384644, Vollgespeiste Richtantenne für Kurz- und Ultrakurzwellen. http://www.puertobalsillas.com/radio/384644.pdf 384644〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Quad antenna」の詳細全文を読む スポンサード リンク
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