| 摘要 |
An antenna minimizes radiation from the outer conductor ( 44 ) of a coaxial cable ( 40 ) that is coupled to the antenna by providing a balancing tab ( 90 ) that lies near the connection ( 72 ) of the cable outer conductor ( 44 ) to the antenna. One antenna includes a Yagi structure ( 12 ) constructed of a plate of metal that forms a long boom ( 20 ) and a plurality of directors ( 28 ) extending laterally across the boom, with an electrical coupling loop mounted at a rear region of the Yagi structure. The coupling loop includes a folded dipole in the form of a metal coupling plate that forms a loop ( 54 ) with a gap ( 70 ), the loop having a laterally elongated front loop end ( 60 ). The Yagi structure is formed with a balancing tab ( 90 ) that lies forward of the loop, that has a lateral length (D) less than half that of one of the directors, and that extends from only one side ( 22 ) of the boom which is the side to which the outer coax conductor ( 44 ) is connected to the loop. The metal coupling plate lies facewise adjacent to a face ( 24 ) of the Yagi plate, with a dielectric spacer ( 76 ) between them.
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