I remember reading somewhere that one way to determine the optimum
number of buried radials for a vertical antenna is to use a specific
value for the distance between the outer ends. (I'm not sure if this
is the straight-line distance, or the length of a chord, but there
wouldn't be much difference.) But I can't remember the value.
Something like .05 wavelength rings a bell, but I'm not sure. Does
anyone know what the value is and where I might have read it?

Thanks -

Steve W9HJW