Vertically Polarized Dipoles and Monopoles, Directivity, Effective Height and Antenna Factor

The effective length (L_e) of linear antennas like dipoles and the effective height (H_e) of monopoles shorter than a wavelength are determined using a transmitting Hertz Dipole as a reference. Effective Receiving Area (A_eR) has been calculated in the receiving mode and hence the Antenna Receiving Directivity (D_R) or Gain (G_R)) can be determined. From these calculations, it can be seen that the Received Power (W_R) in a link between two dipole antennas in free space or between two monopole antennas over a perfect ground is of the same value in the far field region. As a result, the directivity or gain of the ideal dipole antenna in free space has the same value in transmission and reception; but, a different value for monopole and dipole antennas installed over a perfect ground plane. This result is fulfilled in the ideal as well as the real case where losses and mismatchings are involved.