The Yagi-Uda directional antenna array achieves high forward directive gain through mutual parasitic electromagnetic coupling. Driven by a single active dipole element, currents are parasitically induced in slightly longer rear reflector elements (acting inductively to reflect waves forward) and slightly shorter forward director elements (acting capacitively to reinforce radiation ahead). The superposition of these phase-delayed currents produces an intense forward end-fire radiation lobe with strong front-to-back rejection.