Which of the following antenna types will be most effective as a near vertical incidence skywave (NVIS) antenna for short-skip communications on 40 meters during the day?
A horizontal dipole placed between 1/10 and 1/4 wavelength above the ground✓Richtige Antwort
A vertical antenna placed between 1/4 and 1/2 wavelength above the ground
A horizontal dipole placed at approximately 1/2 wavelength above the ground
A vertical dipole placed at approximately 1/2 wavelength above the ground
Erklärung
NVIS requires energy radiated almost straight up, and a horizontal dipole low over ground has its reflected field adding in phase at the zenith. A vertical concentrates energy at low angles, while a dipole around one-half wavelength high has already begun splitting its pattern away from straight up.