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However, Yagi who provided the conception which was originally vague expression to Uda, always acknowledged Uda's principal contribution towards the design which will currently be recognized as the reduction to practice, and if the novelty is not considered, the proper name for the antenna is, as above, the Yagi–Uda antenna (or array).
A quad antenna is a type of directional wire radio antenna used on the HF and VHF bands. A quad is a Yagi–Uda antenna ("Yagi") made from loop elements instead of dipoles: It consists of a driven element and one or more parasitic elements; however in a quad, each of the loop elements may be square, round
Hidetsugu Yagi (八木 秀次, Yagi Hidetsugu, January 28, 1886 – January 19, 1976) was a Japanese electrical engineer from Osaka, Japan. When working at Tohoku Imperial University , he wrote several articles that introduced a new antenna designed by his assistant Shintaro Uda to the English-speaking world.
Quad antennas are Yagi-Uda antennas made from loops instead of dipoles or monopoles, and are likewise used as a directional antennas on the HF bands for shortwave communication. They are sometimes preferred for longer wavelengths because (if square) they are half as wide as a Yagi built from dipoles and have slightly better directivity.
It is a two element Yagi-Uda antenna with folded dipole elements, and no director(s). Because of the folded ends, the element lengths are approximately 70% of the equivalent dipole length. The two-element design gives modest directivity (about 2.0 dB ) with a null towards the rear of the antenna, yielding a high front-to-back ratio : Gain up to ...
However, a Yagi with the same number of elements as a log-periodic would have far higher gain, as all of those elements are improving the gain of a single driven element. In its use as a television antenna, it was common to combine a log-periodic design for VHF with a Yagi for UHF, with both halves being roughly equal in size.
Outdoor antenna designs are often based on the Yagi–Uda antenna [16] or log-periodic dipole array (LPDA). [17] These are composed of multiple half-wave dipole elements, consisting of metal rods approximately half of the wavelength of the television signal, mounted in a line on a support boom.
The term antenna array most commonly means a driven array consisting of multiple identical driven elements all connected to the receiver or transmitter. A parasitic array consists of a single driven element connected to the feedline, and other elements which are not, called parasitic elements. It is usually another name for a Yagi–Uda antenna.
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