Benchmarking the radiation and efficiency of seawater antennas compared to copper structures based on conductivity effectiveness: a modelling analysis in VHF band

This paper presents a theoretical comparison of seawater monopole antennas based on two modelling approaches: the three-term theory and a classical electromagnetic model based on surface resistance and skin depth. The radiation efficiency and reflection coefficient are evaluated across the VHF band (40–200 MHz), using seawater conductivity values ranging from 3.5 to 6 S/m. Utilizing a genuine physical property of saltwater, and taking into account skin depth, provides enhanced accuracy for several reasons, including actual losses from the seawater. A metal (copper) monopole is included as a reference benchmark, and Matlab has been used to investigate the models. Results show that the enhanced model provides conservative but realistic performance estimates, which agree well with the three-term theory method at low frequencies, but diverge slightly at higher frequencies.