dear friends while i was searching about Formulas of yagi antenna i find this web side and im asking if its right or not coz my teacher said there is no basic for that which is in the internet so dear friends do u have formules that can help me to desgin it
That formula is ok, but in general to get the best performance the Yagi antenna needs some optimization (for elements length and spacing) which depends by some parameters as, thickness of the elements and antenna height from the ground.