Alejandro Lieber wrote
in :

....

Thanks Owen for the Clip053a.png
The results are just amazing.

But I just cann't understand why the current in the radials, don't
induce a significant current in the earth, that ends as an important
lost power.

The model results do not support the common Rules of Thumb (RoT) or
explanations that I have often seen on the subject of elevated radials.

The model suggests that as the 3 radial system is lowered, efficiency
(meaning total power radiated in the hemisphere divided by power input)
changes little until the radials are 100mm above ground, and the
efficiency drops quickly, more quickly as the height approaches zero.

I interpret that to mean that there is little elecric flux in the soil
due to antenna currents for this configuration until the radials are very
close to the soil, and then the loss effects grow very rapidly. I assume
that the losses are mainly due to dielectric effects in normal soils, but
that might be different if you had magnetic material in the soil.

Is this surprising? I think that if you wanted to make a device to warm
soil by dielectric heating using RF, you wouldn't expect it to be very
effective if the conductors weren't very close to the soil.

Using more radials reduces the losses.

If you can visualise the electric field flux in the case of the monopole
over three radials, and compare it to a horizontal dipole, you may get an
insight to why a low dipole is more effective at heating the soil.

Owen