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Tech2025
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How exactly do the elements "connect" to each other to make an antenna directional? I see some Yagi's have a reflector but most do not.
A Yagi antenna is an end fire array of dipoles. Energy is supplied to a driven element via a transmission line, and the remaining dipoles are excited by mutual coupling rather than by the use of a transmission line. Each element has a fairly high Q factor, and so the coupling can be sufficient even when the mutual impedance is small. K=MQ where K is the coupling coefficient and M is the mutual impedance. The mutual impedance is a mixture of reactive and radiative coupling. The required phasing to obtain end-fire action is obtained by de-tuning the elements.Tech2025 said:How exactly do the elements "connect" to each other to make an antenna directional? I see some Yagi's have a reflector but most do not.
really ? ... show us a photoTech2025 said:I see some Yagi's have a reflector but most do not.
What you mean is that the reflector often has a large area. There is always at least a dipole 'reflector'. It reflects because its length is greater than the driven element and the phase of the re-radiated wave from it is opposite (approx) to the phase of the wave from the driven element so there is (partial) cancellation in the rear direction. As has been hinted at above, the simplest form of Yagi is an H antenna which has a roughly cardioid pattern.Tech2025 said:I see some Yagi's have a reflector but most do not.
Early work on some very successful Yagi arrays was done decades before the dreaded simulations were available.berkeman said:For more elements it looks like simulations are used to optimize the gain and directivity..
A yagi antenna, also known as a Yagi-Uda antenna, is a type of directional antenna commonly used in radio and television applications. It is named after its inventors, Japanese scientists Hidetsugu Yagi and Shintaro Uda.
A yagi antenna works by using a series of elements, including a driven element, directors, and a reflector, to focus and amplify radio waves in a specific direction. The elements are arranged in a specific pattern and size to create a narrow beam of radiation, making the antenna directional.
A yagi antenna is directional because of its design and construction. The elements of the antenna are arranged in a specific direction, and the dimensions of each element are carefully calculated to focus the radiation in that direction. This makes the antenna more efficient at transmitting and receiving signals in that specific direction compared to other directions.
Several factors can affect the directionality of a yagi antenna, including the spacing and size of the elements, the number of directors, and the length and angle of the reflector. Additionally, the frequency of the signal and the type of terrain can also impact the directionality of the antenna.
Yagi antennas have several advantages over other types of antennas, including their high directionality, efficiency, and gain. They are also relatively easy to construct and can be used for a wide range of applications, such as point-to-point communication, television broadcasting, and satellite communication.