TABLE OF CONTENTS Heinrich Hertz was the first to compute the radiation of an electric dipole and he also published the first diagrams showing the development and outward propagation of the field radiated from the dipole [1 4]. In his derivation of the electromagnetic field excited by a short electric dipole he introduced a vector quantity that is named after him the Hertz vector.
We compute the radiation field of a short straight wire segment with impressed harmonic current. The length h of this conductor is assumed to be small compared to the wavelength. Therefore the current I may be considered to be uniform over the length h of the wire segment. Such an arrangement is called a short electric dipole or Hertzian dipole. In his early experiments, Heinrich Hertz realized such a dipole by attaching spheres at the end of the line segment. These spheres are storing the charge accumulated at the end of the wire, if a uniformly distributed current is flowing through the wire. Complex wire antennas or other radiating wire structures may be modeled by segments of Hertzian dipoles. The current I 0 may be impressed at some intersection introduced into the Hertzian dipole. For r much larger than h we may consider the polarization excited by the current I to be concentrated into the origin. From (4.103a) we obtain under this assumption the approximate solution for the Hertz form
| (12.1) |  |
Due to (3.23), the impressed electric polarization 
