We have been focusing on wireless LAN for radiocommunication between ships for exchanging safety and efficiency navigational information each other. In the preceding trial, we used directional antennas and measured RSSI (Received Signal Strength Indication) and throughput between ships. However, the trial was held with one ship moored at the peer. In this time, we carried out on-sea trial by sailing two ships. The parameters of the trial were ship's speed (3 cases), passing distance (2 cases) and type of directional antenna (2 cases). Twenty-four trial series were done in two days. By this trial, following results were obtained. First, the radiocommunication ability did not fall by sailing both two ships. Second, comparing the speed different cases, it was appeared that the trim angle, which became larger at high speed on the small ship, did not affect the radiocommunication performance, because the E-plane half-power angle of the antenna was much wider than the trim angle. Last, the wider the bearing angle became, the lower RSSI became, depending on the E-plane half-power angle of the antenna. However, the throughput was over 1 Mbps and transferred data size was over 50-100MB in any case.
