Design and Fabrication of Square Top-Loaded Monopole Antenna as the Loran Transmitter with Four Masts

In this paper design method and measurement results of the antennas with square-toploadings (STL) as the modified versions of sectionalized Loran transmitter (SLT) antennas are presented. An advantage of the proposed antenna is the improved reactance using additional toploaded wires. Comparison between the proposed antenna and previous structures indicates that the radiation resistance is multiplied by two and the realized gain is improved 6 dB. The final structure with 100 m height is fabricated and its photographs are indicated. The radiation pattern of the realized antenna is obtained by turning around the antenna and recording the power amplitude. The position of each point is obtained using GPS and the distance differences are compensated for the radiation pattern. Therefore a symmetrical pattern is obtained and only the effects of natural objects like mountains or large buildings are observed in the radiation pattern. Finally, the antenna impedance is measured using vector network analyzer and the predicted results are validated successfully.