皮皮学，免费搜题
登录
搜题
【单选题】
垂直接地天线(GP)的构造为电气长度为1/4波长的垂直振子加一个“接地”反射体,因其简单而被大量应用于手持和车载业余电台,但这种天线的实际工作情况往往与理论值相差较大,尤其在频率较低的频段。最常见的原因和改善办法是:A.
缺乏有效的接地反射体。GP天线必须有足够大的接地反射体来形成振子镜像，否则谐振频率和阻抗都将与理论值有显著偏差，应尽量用大面积金属体与天线的接地端直接连接
B.
1/4波长垂直振子太短。改成1/2波长即可解决问题
C.
1/4波长垂直振子太短。在振子中串联加感线圈即可解决问题
D.
一般天线与电缆直接相连，匹配不良。在天线和电联之间加接“巴伦”即可解决问题
拍照语音搜题，微信中搜索"皮皮学"使用
参考答案：
参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【简答题】A．He is not equal to the job. B．He is not well paid for his work. C．He doesn't think the job challenging enough. D．He cannot keep his mind on his work.
【简答题】A．He is not satisfied with the pay. B．He is not able to enjoy paid holidays. C．The job is not very challenging for him. D．There is no hope of promotion.
【简答题】A. Because he is not equal to the job. B. Because he is not well paid for his work. C. Becausehedoesn'tthinkthejOB ischallengingenough D. Because he cannot keep his mind on his work.
【单选题】于是 1658年捷克的教育家夸美纽斯出版了专门为儿童的教科书( ),这本书标志着人类对儿童的认识有了一个飞跃性的转折——童年开始被当作一个独立的人生阶段。
A.
《世界图解》
B.
《儿童的第一本书》
C.
《爱弥儿》
D.
《不不园》
【单选题】B/S结构的描述错误的是哪一项?
A.
B表示客户端浏览器，S表示服务器
B.
需要在服务端使用Web服务器
C.
该构架中的数据库只能采用mySQL
D.
客户端发送请求，服务端响应，并将客户端的请求资源发送给客户端
【单选题】捷克教育家夸美纽斯在1658年出版了(),以绘画的形式介绍了幼儿百科知识,是世界上最早的幼儿图画书。
A.
《五卷书》
B.
《世界图解》
C.
《爱弥儿》
D.
《鹅妈妈的故事》
【单选题】A.Because he is not equal to the job.B.Because he is not well paid for his work.#
A.
Because he is not equal to the job.
B.
Because he is not well paid for his work.
C.
BecausehedoesntthinkthejOB ischallengingenough
D.
Because he cannot keep his mind on his work.
相关题目：