Extra exam question E9D12

WhyA Yagi's parasitic elements are made longer or shorter than resonance to control the phase shift between them and the driven element. A Yagi's parasitic elements are deliberately made either longer or shorter than resonance specifically to control the phase shift between the current induced in them and the current in the driven element, which is exactly what makes them behave as a reflector (element made longer) or director (element made shorter) rather than just another resonant radiator, answer C. It isn't done for wind torque cancellation, mechanical balance, or to minimize losses, those aren't the electrical reason parasitic element lengths are detuned from resonance.