Total posts : 45366
Below for consideration are some comments prompted by parts of the post of kk7cw.
Ground radials, either elevated above ground or below the surface, work more uniformly if they cover 360 degrees around the antenna.
Radials elevated more than a few feet above the ground, and in the horizontal plane, behave much differently than when they are buried. Dr. George Brown, the inventor of the ground-plane antenna stated that only two ~1/4-wave radials extending in opposite directions from the base of an elevated, 1/4-wave vertical radiator gave the same free-space pattern gain/shape as for a 1/2-wave dipole, and that using more than two elevated radials gave no benefit. NEC modeling also confirms this.
However, understanding the ground potential of the radials is what the vertical antenna works against, any ground radials 5% longer than the actual length of the antenna is sufficient to raise the radiation efficiency of the antenna.
The true function of ground radials is to collect the r-f currents induced into the earth by radiation from a vertical antenna. These earth currents exist out to a radius of at least 1/2 wavelength, regardless of the antenna height, and need to be delivered back to the “ground” terminal of the tx+antenna system in order to maximize radiation from the vertical radiator.
A few ground rods around the base of the antenna will provide a connection to “ground potential,” but they will be a lossy means of collecting the r-f currents at distances of 1/2-wave and more from the antenna — which have to travel that distance through a poorly conducting earth to reach them.
Field studies done in 1937, and verified in thousands of installations since prove that the radiation efficiency of even an electrically short antenna will benefit from using a large number (up to 120) of buried radials of longer length (up to ~1/2-wave) than the antenna height itself.
Those same field studies also show that if only a few buried radials are used, they may as well be “short” (maybe 0.1-wavelength), because the additional r-f current that those few radials would collect if longer is very small. But of course a ground system using only a few short, buried radials is far less effective than one with more/longer buried radials, regardless of the antenna height.