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?
Why A horizontal dipole interacts with its reflected image in the ground, which is 180 degrees out of phase. As the antenna gets very low, that out-of-phase image increasingly cancels the radiation, so the radiation resistance and hence the feed point impedance drops steadily, heading toward near zero at zero height. Above roughly 1/5 wavelength the impedance wiggles around the free-space value of about 73 ohms, but below that it falls off continuously, so a dipole at 1/10 wavelength shows a noticeably lower impedance than 73 ohms.
Watch out The choice about a peak near 1/8 wavelength confuses low heights with the higher region, around 0.3 to 0.4 wavelength, where the impedance actually rises above 73 ohms. The claim that height has no effect ignores ground reflection entirely, which also controls the takeoff angle.
Low dipole, low impedance: the ground image cancels it. Only vertical monopoles like being near ground.