在甚高频(VHF)频段上,发射天线的输入阻抗随环境和天气条件的变化而变化,如暴雨或严重裹冰等情况会引起一定的变化,从而影响馈线的匹配情况,使发射机的工作状态以及输出功率也跟着发生变化。为了监视这种变化,往往需要在发射机内对输出功率以及馈线驻波比进行测量。对于自动化、无人值班的发 In the VHF frequency band, the input impedance of the transmitting antenna changes with the environment and weather conditions, such as heavy rain or severe ice wrapping will cause some changes, thus affecting the matching of the feeder so that the transmitter’s Working conditions and output power also followed change. In order to monitor for this change, it is often necessary to measure the output power and the VSWR of the feeder in the transmitter. For automated, unattended hair