Yagi antennas are formerly known as Yagi-Uda antennas. Actually it was Shintaro Uda in 1926 who invented this type of antenna, but it was Hidetsugu Yagi who filed for the patent and didn’t include Uda’s name in the application.
A Yagi antenna consists of a driver element, usually in the form of a dipole or folded dipole. The other main parts of this antenna are the reflector element, and the driven elements.
The Yagi-Uda antenna has many benefits.
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They are directional types of antennae which offer a good gain in signal. It comes with a beam width of 50° to 70°.
- Yagi-Uda antennas have significant signal polarity. They should be mounted either vertically or horizontally, depending on the orientation of the receiving antenna.
- These antennas are directional and offer good gain.
4. Yagi-Uda antennas are popular with local club communication, communicating with boats off-shore, satellite communication and field days.
These antennas typically operate in the HF to UHF bands (around 3 MHz to 3 GHz), although their bandwidth is usually small, on the order of a small percentage of the center frequency.
An image of Professor Yagi with a Yagi-Uda antenna is shown.
Design
The development of the guide antennas is generally carried out on the basis of the experimental data. The required directional diagram can be obtained with a different number of dipoles, different distances between them, different settings of them. However, it is necessary to tend to obtain the desired pattern provided that the dimensions of the antenna are minimal.
The lengths of the elements and their separation are not very critical, allowing variations in length and 1 to 5% of separation. The length of the reflector is approximately 5% greater than the dipole and this 5% greater than the director. Sometimes you tend to increase the size of the reflector and reduce the size of the directors, thus increasing the bandwidth of the antenna. If the reflector is smaller than the dipole and it is smaller than the directors, the effect will be totally harmful and cancels its behavior.
The dipole is not counted as an element, this is an essential factor and its existence is taken for granted in the diagram, an antenna of one element is made up of a dipole and a reflector, the antenna of two elements of a reflector, a dipole and a director.
