用于业余无线电的接收——发射天线,较多地采用大型的双极天线,其效果好。但架设天线占地大且不能随意移动。鞭状天线简单、轻便,但接收效果不好。单方面加长天线,尽管可以增大接收信号电平,但噪声同时也增大,因此,信噪比并未得到明显改善。众所周知,通常接收到的业余电台信号场强只有短波广播电台的千分之一甚至更弱。有时反而因加长天线感应了较多的噪波而淹没了有用的业余电台信号。用定向的 For amateur radio receiver - transmitting antenna, the use of more large bipolar antenna, the effect is good. But the erection of the antenna covers a large area and can not move freely. Whip antenna is simple, lightweight, but the reception is not good. Unilaterally lengthening the antenna, although it can increase the received signal level, but the noise also increases, so the signal to noise ratio has not been significantly improved. As we all know, the signal strength of amateur stations that are usually received is only one-thousandth or less than that of short-wave radio stations. Sometimes, however, the useful amateur radio signal is overwhelmed by the prolonged antenna sensing more noise. With directional