Vertical Monopole Antenna Research Articles

AM broadcast antennas with elevated radial ground systems

Results are presented of computer modeling studies indicating that an elevated vertical monopole antenna with four elevated horizontal radials produces more ground-wave field strength than does a conventional ground-mounted monopole with 120 buried radials. For the analysis, the length of the radials and the height of the monopole were set equal to 0.25 of the free-space wavelength, and the frequency of operation was fixed at 1.0 MHz. Three different sets of ground constants were used, simulating averaging, very good, and very bad soil electrical parameters in accordance with the Numerical Electrical Code (NEC-GS). >

Monopole antenna on circular disk over flat earth

The sinusoidal-Galerkin moment method is developed for a vertical monopole antenna at the center of a circular disk over the flat earth. Numerical results are included for antenna impedance and current distribution.

Analysis of monopole antenna erected on circular conductor

AbstractA vertical monopole antenna erected on the base of a circular cone is analyzed by the equivalent edge current (EEC) and the geometrical theory of diffraction (GTD). The cone may be converted into a disk, column or truncated cone. The current distribution and input impedance are calculated by the moment method. The multiple diffraction on the circular plane is considered in the calculation of radiation patterns by the EEC method (or GTD). The experimental results agree approximately with the calculation.

Excitation of the Whistler Mode in the Ionosphere by Leakage From VLF Guided‐Wave Modes

The penetration of VLF waves into the ionosphere is calculated from the mode representation of the fields in the earth‐ionosphere waveguide. This calculation is more appropriate for evaluation of leakage of VLF energy into the ionosphere at large distances from the transmitter than is the calculation based on a ray theory representation of the fields. The ratio of the amplitude of the field excited in the ionosphere to that observed on the earth is found to agree with the observations of the LOFTI I experiment.In carrying out the analysis of the leakage of energy from the waveguide modes, it is necessary to reevaluate the modal propagation constants, employing a self‐consistent calculation requiring that the wave polarization of a modal field be preserved upon reflection at the waveguide boundaries. Upon imposing these conditions, it is found that two sets of modes result, having different polarizations. These sets of modes have been designated as quasi‐TE and quasi‐TM.by Budden, but both sets tire no1 usually used in VLF field strength calculations. Under nighttime conditions, both types of modes will be of importance, while in daytime only the quasi‐TM modes will be excited by a vertical monopole antenna on the earth. These results predict a nonreciprocal attenuation over a north‐south propagation path.