[BC] Ground system

[Richard Fry]

Earlier...

> ...remember, the ground system is half of a dipole.

The difference being that each half of a dipole generates useful, far-field 
radiation.

But all of the useful, far-field radiation from a vertical monopole 
originates from the vertical section only, not from buried (or elevated) 
horizontal radials.

The real function of buried radials used with a monopole is to improve the 
conductivity of the earth over as much as possible of an area of 1/2-wave 
radius around the base of the monopole.  That area of the earth contains r-f 
currents produced by the fields radiated by the vertical monopole, and those 
currents need a low resistance path back to the r-f ground terminal of the 
transmit system in order for it to radiate efficiently.

The r-f loss of that area of the earth is a series circuital element of the 
transmit system, and determines how much of the power applied to the antenna 
system is radiated as EM energy, rather than heating up the earth around the 
monopole.

The paper at 
http://i62.photobucket.com/albums/h85/rfry-100/GroundCurrentNearMonopole.gif 
goes into some detail about this.

RF