Measured azimuthal antenna patterns of a US Coast Guard patrol boat show significant variations of 3 to 9 dB in signal strength caused by sea waves. MININEC was used to model the antenna configurations and to predict the azimuthal radiation patterns and impedances for the various frequencies. MININEC can successfully model azimuthal antenna patterns, but cannot model the effects of sea waves and winds. It is noted that the varying 3 to 9 dB ripples in signal strength could mean the difference between communicating and not communicating. This observation has been confirmed by discussions with patrol boat personnel.
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