Walter Maxwell wrote:

In my previous post above I forgot to mention that the displacement currents
that enter the ground between the radials don't follow the lossy ground to the
center of the radial system. Instead, they quickly diffract to the nearest
radial and thus continue toward the center along the radial wire. Consequently,
the more radials the shorter distance the diffracted current has to travel to
reach the higher conductivity of the wire. The last I knew the FCC requires only
90 radials (every 4°) to comply with the regulations, but many BC antenna
engineers use 120 (every 3°).

I discussed this issue in Chapter 5 in both the 1st and 2nd editions of
Reflections, with a diagram of the diffraction phenomenon in Fig. 1.

This interaction among radials has quite a dramatic effect on the
effective ground conductivity. I noticed and reported quite some time
ago that Reg's ground radial program produced answers which disagree
strongly with both BLE and NEC-4 modeling (which agree with each other
reasonably well), and speculated that he didn't account for this
interaction in his program. (I haven't checked since to see if the
program has been modified.) All he says about having to trust the writer
of the program if you don't have access to the source code is true.

Roy Lewallen, W7EL