Changes

A short dipole is the simplest way of exciting a structure in [[EM.Terrano]]. It is also the closest thing to an omnidirectional radiator. The direction or orientation of the short dipole determines its polarization. Note that EM.Terrano does not offer an isotropic radiator as a source type because it is a polarimetric ray tracer. A short dipole source acts like an infinitesimally small ideal current source.  To define a A short dipole source, follow these steps: * Right click on the '''Short Dipoles''' item in the '''Sources''' section of the Navigation Tree and select '''Insert New Source...''' from the contextual menu. The Short Dipole dialog opens up.* In the '''Source Location''' section of the dialog, you can set the coordinate of the center of the short dipole. By default, the source is placed at the origin of the world coordinate system at (0,0,0). You can type in new coordinates or use the spin buttons to move the dipole up from the default global ground.* In the '''Source Properties''' section, you can specify the '''Amplitude''' in Amperes, the '''Phase''' in degrees appears as well as the '''Length''' of the dipole a small arrow in project units.* In the '''Direction Unit Vector''' section, you can specify the orientation of the short dipole by setting values for the components '''uX''', '''uY''', and '''uZ''' of the dipole's unit vector. The default values correspond to a vertical (Z-directed) short dipole. The dialog normalizes the vector components upon closure even if your component values do not satisfy a unit magnitudescene. The radiation resistance of a short dipole of length ''dl'' is given by: :<math> R_r = 80\pi^2 \left( \frac{dl}{\lambda_0} \right)^2 </math> The radiated power of a short dipole carrying a current I₀ is then given by: :<math> P_{rad} = \frac{1}{2} R_r |I_0|^2 = 40\pi^2 |I_0|^2 \left( \frac{dl}{\lambda_0} \right)^2 </math>