How does the feed point impedance of a horizontal 1/2 wave dipole antenna change as the antenna height is reduced to 1/10 wavelength above ground?
It steadily increases
It steadily decreases✓Правильный ответ
It peaks at about 1/8 wavelength above ground
It is unaffected by the height above ground
Объяснение
The earth acts as a mirror that inverts the phase of a horizontally polarized antenna, and as the dipole is brought close to that image the cancellation reduces its radiation resistance, so the feed point impedance falls steadily as the height drops toward 1/10 wavelength.