4nec2 wrote:
"When someone asks me what`s the optimal radial ground screen, I mostly
answer: 120 radials with a length of 0,4 lambda."

That`s sufficient, but RCA`s Brown, Lewis, and Epstein did extensive
research in the mid-1930`s resulting in an FCC requirement of 120
radials with a length of 0.25 wavelengrh, equally spaced around the base
of a tower.. It wasn`t exactly what B, L, & E had recommended but it
became the minimum for broadcasters.

For amateurs, my 19th edition of the ARRL Antenna Book has a Table 1 on
page 3-3 that is more economical.

I seem to remember that Reg J. Edwards had a program for optimising
padials and I think it is still available.

Best regards, Richard Harrison, KB5WZI