Richard Harrison wrote:
. . .
The FCC`s 120 radials of 1/4-wavelength has been efficient for medium
waves in thousands of instances in all types of soil. It`s overkill in
highly conductive soil, but regulations must be somewhat uniform for
satisfactory enforcement. FCC`s rule is based on B,L,& E`s research. As
I recall, B, L, & E worked at 3 MHz.

We should always be careful in applying commercial broadcast standards
to ham radio. For a broadcaster, the gain of a few percent in radiated
field represents a measurable increase in the audience size, hence a
significant increase in annual revenue, so it's worth a considerable
one-time cost. For most amateurs, it represents only a fraction of a dB
of signal strength, so isn't worthwhile.

Roy Lewallen, W7EL