前言越短波天线主要电气参数有:增益、方向性图、驻波比、输入阻抗及工作带宽等。其中增益是决定通信系统性能的最重要参数。一个天线的设计,除了理论计算分析外,如何精确地测量天线增益是个值得探讨的问题,尤其是超短波天线增益的测量。由于地面反射场的存在,模拟自由空间十分困难,致使天线增益测量产生较大误差。例如:同一个四元八木天线,工作频率,f_0=80MHz,天线长度L=0.5λ。有的测得增益G_D=7dB,有的测得G_D=9dB,有的测得G_D=10dB。而依理论计算,八木天线相对于标准半波天线 The shorter the foreword The main electrical parameters of the antenna are: gain, directional pattern, standing wave ratio, input impedance and working bandwidth. The gain is the most important parameter that determines the performance of the communication system. An antenna design, in addition to the theoretical calculation and analysis, how to accurately measure the antenna gain is a question worth exploring, especially the gain of ultra-shortwave antenna measurements. Due to the presence of the ground reflection field, it is very difficult to simulate the free space, resulting in a large error in the antenna gain measurement. For example: the same four yuan Yagi antenna, operating frequency, f_0 = 80MHz, antenna length L = 0.5λ. Some measured gain G_D = 7dB, some measured G_D = 9dB, some measured G_D = 10dB. According to theoretical calculations, Yagi antenna relative to the standard half-wave antenna