No other antenna has a better relation between gain and expense than the 2-Element-Yagi. One element additional to the dipole will give you 4dB gain. Each further element will give much more mechanical problems and the increase in gain is only 1-2dB for the same bandwidth. What says the ARRL-Antenna-Book about this antenna? "The must bang for the buck". Right!Because the 10m, 15m and 20m-Bands need a greater bandwidth, the radiation resistance must be higher than for the smaller WARC-Bands. Therefore we take the Yagis with radiator-reflector and 50Ohms for 10m (greatest bandwidth), 28Ohms for 15 and 20m and the Yagis with radiator-director and 28Ohms for the WARC-Bands.If you have a height above ground of 10m or higher for a 12m-Yagi, you can try a 12,5Ohm-type for that band. The antenna needs a very clear surrounding! With a very short boom and small bandwidth you get very high F/B. |

**Gain, F/B, Boomlength and Elements of the 50-Ohm-Yagi with Reflector**

Band | Impedance | Gain | F/B | Boom | Radiator | Reflector |

10m | 50Ohm | 4,0dBd | 10,5dB | 1,76m | 4,93m | 5,36m |

**Gain, F/B, Boomlength and Elements of the 28-Ohm-Yagis with Reflector**

Band | Impedance | Gain | F/B | Boom | Radiator | Reflector |

15m | 28Ohm | 4,2dBd | 10dB | 1,61m | 6,87m | 7,22m |

20m | 28Ohm | 4,0dBd | 10dB | 2,30m | 10,26m | 11,08m |

**Gain, F/B, Boomlength and Elements of the 28-Ohm-Yagis with Director**

Band | Gain | | Boom | Radiator | Director |

12m | 4,3dBd | 14,5dB | 1,18m | 6,05m | 5,60m |

17m | 4,5dBd | 13,5dB | 1,70m | 8,32m | 7,80m |

30m | 4,4dBd | 14dB | 3,00m | 14,92m | 14,04m |

**Gain, F/B, Boomlength and Elements of the 12,5-Ohm-Yagi for 12m with Director**

Band | Gain | | Boom | Radiator | Director |

12m | 4,4dBd | >25dB | 0,67m | 6,09m | 5,78m |

A quarter-wave choke of coax is grounded at the socket.50Ohm: Single Lambda/4*V-coax 50Ohm28 Ohm: 2xLambda/4*V-coax 75Ohm parallel12,5 Ohm: 2xLambda/4*V-coax 50Ohm parallel Length of the cables see table below |

**Lengths of the Lambda/4-coax for the choke:**

Band | Lambda | Full-PE V=0,667 | Foam-PE V=0,82 (CATV) |

10m | 10,60m | 1,77m | 2,17m |

12m | 12,03m | 2,00m | 2,47m |

15m | 14,18m | 2,36m | 2,90m |

17m | 17,53m | 2,76m | 3,60m |

20m | 21,18m | 3,53m | 4,34m |

30m | 29,62m | 4,94m | 6,07m |