In this paper we assess the influence of the conductivity of the medium on the radiation characteristics and input impedance of a loop antenna designed for underwater communications. The initial study is based on simulation of the antenna characteristics using FEKO electromagnetic (EM) software. Additionally, an equivalent circuit model of the antenna is also obtained and simulation of the input impedance on ADS software shows good agreement with the EM simulator. It is found that the radiation pattern, of the loop antenna changes significantly with the conductivity of the medium, from freshwater to seawater. The loop antennas were built with baluns and tested in freshwater, where the insertion loss between two identical antennas and the radiation pattern of one of them were also measured. The results show good agreement with the simulations.

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