![]() As Yagi Uda antenna is commonly known as Yagi and is refers as directional antenna. The design of antenna relates to the radiation pattern which refers to the dependence of directional radiation from antenna. Typically, the reflector element is 5 % longer than the driven element and the director is 5% shorter than the driven element. The reflector reflects RF energy and the director directs the RF energy. The other three outer elements are called parasitic elements. It is termed the ‘driven element’ because it is only element that is directly connected to the FM transmitter circuit, driving the entire antenna. The middle element is the simple half-wave, folded dipole. The above fig shows a Yagi antenna consisting of four elements. Basically a Yagi antenna consists of one reflector (in the rear), one driven element and one or more directors (in the direction of direction/reception). For the highest gain or discriminating against an interfering signal 20deg-40 deg azimuth off the desired signal, we use a Yagi antenna. A well designed Yagi antenna as per the design given below can cover a line of site distance of even 5 KMs with just 1 watt RF power. It has the best gain for its sizes and a correspondingly narrow main lobe (beam). The Yagi antenna is a narrow-band antenna designed to work only on FM channel.
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