8 wood antenna

  8 wood antenna is one kind is brought to aerial, by an active many passive Zhenzi places Zhen Zihe to go up in same plane, and perpendicular at join the metallic lever of their center. General a passive brace up child for reflector, the passive of the others brace up child for director. Because metallic lever is passed brace up child the voltage wave node that go up, line of perpendicular Yu Tian, so, metallic staff is very small to the near field influence of aerial. And
Active brace up child must be isolated from with metallic lever.
   The data that expresses through falling can see, perpendicular antenna reachs the gain prep above of 8 wood antenna occasionally extremely aerial. (Pick from " aerial electric wave travels " , xu Kun of northward traffic university unripe, Jiang Zhong emerges compile)

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Aerial form   Reflector number Director number Active brace up child several   Directional coefficient

  Occasionally extremely       0      0        1         0 DB
2 unit 8 wood      1      0        1    3 ~ 4. 5 d B
2 unit 8 wood      0      0        1    3 ~ 4. 5 d B
3 unit 8 wood      1      1        1      8 d of 6 ~ B      
4 unit 8 wood      1      2        1      10 d of 7 ~ B
5 unit 8 wood      1      3        1      11 d of 9 ~ B

   From go up on the watch knowable, the unit of 8 wood antenna is more, directional stronger. But unit addition not with directional into direct ratio. When unit is overmuch, bring about narrow of working frequency band, whole antenna dimension also will slant big.

   In shortwave wave band, wavelengh is longer, abstain 8 wood antenna to compare difficulty, in ultrashort wave band (V / U) , because wavelengh is short, can compare the convenient 8 wood antenna that contains low cost.

   The mathematical calculation of 8 wood antenna is complex (I encounter mathematical derivation to feel dazed to the head goes up) , nevertheless a lot of projects or academic literature give out its dimension, want according to only these data, OK and self-restrained give a pair of pretty good YAGI!
    The dimension of 8 wood antenna joins 5 unit graph 1

   If abstain 4 unit 8 wood antenna, it is OK to should not install director D only, aerial also can appear a bit more cabinet. If think make it 7 unit, going up two director unit is added on the foundation of the graph, length is the 84 % of half wavelengh respectively, 82 % . 0 the unit interval that adds newly still is wavelengh. 2 times.

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