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词汇 Turnstile antenna
分类 英语词汇 英语翻译词典
释义

Turnstile antenna

英语百科

Turnstile antenna

An axial-mode turnstile antenna for 136-137 MHz LEO weather satellites comprising a single turnstile crossed dipole above a passive set of dipoles serving as a reflector.High gain axial mode Yagi turnstile array used to communicate with weather satellites on 136-137 MHz at Bedu, Belgium.  Each component of the array consists of two 9-element Yagi antennas mounted on the same axis at right angles and fed in quadrature to radiate a narrow beam of circularly polarized radio waves
(left) First turnstile antenna, a normal-mode array built by station W8XH, Buffalo, NY, in 1936 that broadcast on 41 MHz (right) Normal-mode turnstile (lower antenna) for NBC's  experimental 46.5 MHz TV station W2XBS  (lower), Empire State Building 1939.  The cigar-shaped elements gave antenna a wider bandwidth of 30 MHz necessary for TV transmission.

A turnstile antenna is a radio antenna consisting of a set of two identical dipole antennas aligned at right angles to each other and fed in phase quadrature; the two currents applied to the dipoles are 90° out of phase. The name reflects the notion the antenna looks like a turnstile when mounted horizontally. The turnstile antenna is often referred to as crossed dipoles. The antenna can be used in two possible modes. In normal mode the antenna radiates horizontally polarized radio waves perpendicular to its axis. In axial mode the antenna radiates circularly polarized radiation along its axis.

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