Production of eight wood antennas, YAGI Antenna
Keywords: eight wooden antenna design
Eight wooden antennas is a lead antenna, which is placed on the same plane from an active vibrating and a plurality of passive vibrators and is perpendicular to metal rods connecting their center. Generally, a passive vibrator is a reflector, and the remaining passive vibrator is a leader. Because the metal rod passes through the voltage wave node on the vibrator, the metal rod has a small influence on the antenna of the antenna. The active vibrator must be insulated from the metal rod. As can be seen by the data below, the gain of the eight wooden antenna is higher than the vertical antenna and dipole antenna. (Excerpted from "Antenna Electric Wave Communication", Northern Jiaotong University Xu Kunsheng, Jiang Zhongyong) Antenna Form Reflector Number The number of active vibrators Directional coefficient dipole 0 0 1 0 dB two unit eight wood 1 0 1 3 ~ 4 .5db two units eight wood 0 0 1 3 ~ 4.5dB three unit eight wood 1 1 1 6 ~ 8dB four unit eight wood 1 2 1 7 ~ 10db five unit eight wood 1 3 1 9 ~ 11db can be seen from the above table, the unit of eight wood antennas The more, the stronger the directionality. However, the increase in units is not proportional to the directionality. When the unit is too much, the working frequency band is narrowed, and the entire antenna size will also be large. In short-wave band, the wavelength is longer, and the self-made eight wood antennas is more difficult. In the ultra-short wave band (V / U), the wavelength is short, and it is more convenient to make a homemade low-cost eight-wood antenna. The mathematical calculation of the eight-timber antenna is complex (I am experiencing the math derivation, but many projects or theoretical books give its size, as long as they can make a good YAGI! The size of the five units eight wooden antennas is incorporated in FIG. 1 If the homemade four units eight wooden antennas, as long as the leader D is installed, the antenna will look small. If you want to make a seven units, two leader units are added on the basis of the above, and the lengths are 84%, 82%, respectively. The spacing of the newly added unit is still 0.2 times the wavelength. I did the 70cm band eight wood antenna, which was originally four units, each vibrator, and a metal rod therefor, made of copper welding (diameter 2.5 mm) provided by BG4RUV. About one month later, I bought a copper strip of 2 meters long and 4mm in diameter. It has also made a detachable four-unit eight-timbene antenna (find a rectangular copper tube as a struts to connect the respective vibrators, each vibrator is used for screws and support The rod is fixed and easy to carry. The resonance point of the first antenna is less than about 2 MHz, but the SWR is not high in 430 to 440 MHz, and the lowest SWR <1.1, the="" highest="" swr="" is="" not="" more="" than="" 1.="" 4.="" the="" swr="" of="" the="" second="" antenna="" is="" not="" large="" in="" the="" entire="" 70="" cm="" band,="" up="" to="" about="" 1.2.="" later,="" i="" made="" some="" changes="" to="" this="" detachable="" antenna,="" using="" the="" remaining="" materials,="" so="" that="" my="" antenna="" can="" be="" assembled="" into="" four="" units="" eight="" wooden="" antennas,="" or="" it="" can="" be="" assembled="" into="" seven="" units.="" if="" you="" want="" to="" make="" an="" eight-timber="" antenna,="" it="" is="" not="" required="" to="" be="" strong,="" you="" can="" try,="" do="" a="" three-unit="" eight-timbera.="" it="" is="" given="" here="" (figure="" 2).="">
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