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河南省周口地区广播局试制了安装在边宽50cm拉线塔上的四层四面组合的双环天线。该发射天线的功率增益约为9dB,驻波比1.1以内的频带宽度为23MHz。单元天线的驻波比1.1内的频带宽度达50MHz,占设计频率的20%以上。该天线使用两年来稳定可靠,效果良好。本文简单介绍圆环周长为1.2波长的双环天线的工程近似计算法,用支撑腿上的金属片补偿电容的频带展宽法,以及电缆变阻器采用一段容性电缆并终接半可变电容的补偿方法.文末还对天线的功率增益进行了粗略的讨论。
Zhoukou Prefecture, Henan Province, Bureau of Radio trial installed in the width of 50cm cable tower four-layer combination of four-ring antenna. The transmit antenna has a power gain of about 9 dB and a bandwidth within a standing wave ratio of 1.1 is 23 MHz. The bandwidth of the unit antenna in the standing wave ratio of 1.1 is 50 MHz, accounting for more than 20% of the designed frequency. The antenna used two years to be stable and reliable, good effect. In this paper, a simple approximation of the engineering calculation for a double loop antenna with a perimeter of 1.2 wavelengths is presented. The band broadening method is used to compensate for the capacitance of the metal sheet on the support leg, and a section of capacitive cable is used for the cable varistor to terminate the compensation of the semi-variable capacitor Method.At the end of this article, the power gain of the antenna is also discussed roughly.