One of the most used and most well known antenna’s
Invented by Yagi-Uda in Japan the Yagi is a Directional antenna, the Yagi exhibits more gain than any other antenna, and some amateur Yagis have many directors.
That said optimal spacing is the key, some of the biggest stations use seven element beams with massive boom lengths to achieve great results.
Yagi antenna’s can also be used in another way to most, they can have the elements crossed (Forming an + shape) both fed independently, giving a horizontal and vertical polorisation, but as well as that by using a phasing harness you can clockwise and anti-clockwise polarize the antenna for Satellite work or EME
The theory is quite straight forwards for designing them, I will not even try but instead direct you to this website
In keeping however with the rest of the site I will give the following based on a 5 element 144 Mhz beam, in free space.
144Mhz Yagi SWR
144Mhz Yagi Far Field Plot
144Mhz Yagi Far Field Plot