[600MRG] NDB Antenna Calculator

[Rudy Severns]

Steve, he's going to have a real problem.  Rg depends not only on soil
electrical characteristics and details of the radial system but also on the
antenna over the radial system.  If you have NEC4 determining Rg from
modeling is easy.  Direct calculation is also possible, I've done it, but
it's complex because you have to start by deriving the E and H field
intensities associated with the antenna in the near-field.  From that you
can calculate the soil losses which determine Rg for a given Io.

 

Too many people believe that a given radial system, at a given frequency,
with given soil characteristics, has a fixed Rg.  This is false.  Rg will
depend on all those things plus the details of the vertical.  This is
carefully explained in section 3.2.3 of the 22nd edition of ARRL Antenna
Book which shows among other things the dependence of Rg on the vertical
height for a given ground system.  

 

73, Rudy N6LF