K9EZ wrote:How would this compare to the 120 radials?
It is slightly better than such a system in pristine condition. Radial systems with 120 buried conductors each about 1/4 physical wavelengths long have an ohm or two of r-f resistance, which means that the groundwave field intensity at a given distance should be several percent less than calculated for this NEC model (other things equal).
Also would there be any difference with 6 elevated radials?
NEC says No. In fact, NEC says that this model even with two or three symmetrically oriented, elevated radials each of the same physical length as in this model still would have the same gain and h-plane circularity as with four, six, or more such elevated radials.
The average r-f current in each of more than four elevated radials will be less than in my NEC model, but that should be the only practical difference.
Also note that using such an elevated radial system will not produce any significant improvement over that of a conventional AM broadcast r-f ground system of 120 buried radials each about 1/4 of a physical wavelength, which is in reasonable electrical condition.
For a given applied power, radiator and r-f ground, once the groundwave signal is "launched" from a given tx site, there is no practical way to improve its distant field strength. That depends on the relative losses along the groundwave propagation path -- which have nothing to do with the radiator, or its r-f ground (buried or elevated).
But, kindly run all of this by your favorite consultant for confirmation before deciding what might be appropriate for a given set of conditions.