The exchange below was posted on another board, but it might be interesting here as well (discussion invited).
The kickoff was provided by a description at this link: http://www.kiss-ssb.com/testimonials.html
RF (ex-K8CBZ, General; license not renewed after 1967 due to other pursuits in electronics)
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The wires in an elevated counterpoise do not collect returning antenna currents. The source for the total amount of r-f current that flows on them is the return side of the transmission line. An elevated counterpoise needs to have only a few resonant wires, compared to using buried radials (see the NEC analysis I linked to earlier).The bigger the counterpoise in the form of the number of radials will always be more efficient than 1 radial in collecting antenna return currents.
Buried radial wires are not resonant. The v.p. of those conductors when buried is far slower than when they are in free space. They do serve to collect the r-f current flowing in the ground plane. Those ground currents are produced by the displacement currents flowing across the capacitance of the monopole to the earth, and for efficient radiation need to be returned to the transmit system with minimal loss. The paper linked below was made for a "Part 15" board, but should help illustrate this point.
Those r-f currents are present on and somewhat below the surface of the earth from the base of the monopole to a radius of about 1/2 of a free-space wavelength. To collect them rather efficiently the buried radial system needs to use about 120 evenly-spaced conductors, each at least 1/4-wave long in free space wavelength. This was proven experimentally by Dr. George Brown of RCA Labs back in 1937, and that finding has been used by the FCC ever since as a baseline for the performance of AM broadcast stations.
Dr. Brown also invented the ground plane antenna, which is a vertical monopole driven against 3 or 4 elevated quarter-wave conductors -- which form a counterpoise for the vertical section.
A vertical monopole using a counterpoise does not require or use the r-f current flowing in the earth (or sea water) around the antenna site to achieve efficient radiation. The radiation it "launches" is independent of the earth, but reflections of that radiation from the earth will affect its far-field radiation pattern.
While a system of 120 x 1/4-wave buried radials and an elevated counterpoise permit essentially the same radiation pattern and gain from the monopole section, they do it in different ways.
Probably the "600 feet" of wire that bothers some in this thread is a bit of marketspeak, in that the total length of all the series-loaded conductors for the various bands might add up to that length if all those conductors had the physical length to be self-resonant (guessing).
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RF
