Yagi antenna is a directional antenna consisting of an active element and multiple passive elements placed on the same plane and perpendicular to a metal rod connecting their centers. Generally, one passive oscillator is a reflector, and the other passive oscillators are directors. Because the metal rod passes through the voltage wave node on the vibrator and is perpendicular to the antenna, the metal rod has little effect on the near field of the antenna. The active oscillator must be insulated from the metal rod.