Topband: Modeling "Ground" and losses

[Richard Fry]

>The feedpoint connection, in all cases of vertical antennas, whether the 
>system is shunt fed or series fed, or even if it is an end-fed half wave, 
>ties one feed terminal to the ground or counterpoise system. It has to be 
>that way, and the current out into that counterpoise (whatever the 
>counterpoise is) has to be equal to the common mode current at the junction 
>flowing up into the radiator.

The link below leads to a NEC4 comparison of a 1/4WL vertical monopole using 
four 1/4WL radial wires at 90-deg horizontal intervals.  In one case the 
radials are buried.  In the other case they (and the monopole) are elevated 
1 meter above the earth, and not connected to the earth by any metallic 
path.  Applied power in both cases is 100 watts, and earth conductivity in 
both cases is 5 mS/m, d.c.5.

The surface wave fields at 0.1 km from these two configurations differ by 
about 1.15 dB, which means that their radiated powers differ by about 30%.

If the total energy flowing into the monopole system with buried radials is 
dictated only by its hard-wired connection through the transmission line 
back to the transmitter, then what is accounting for the reduction of its 
radiated power?

http://s20.postimg.org/453nz5vn1/160_M_QTR_WV_MONOPOLE_Flds.jpg

R. Fry