Abstract: Maritime Safety Information (MSI) plays a very important role in the navigation safety of a ship.Ships,navigating the sea area of Ningbo-Zhoushan,often face many difficulties when they receive the MSI by HF NBDP broadcasting from Shanghai coast station,especially at night.For example,the receiver can not gain any useful signal because of the poor performance of communication.An analysis on this phenomenon is given in detail by using the knowledge of radio wave communication theory.And on the basis of above analysis,some effective ways to improve the receiving quality are offered to help the ships get MSI when they navigate in the sea area of Ningbo-Zhoushan.

Key words: MSI (Maritime Safety Information), NBDP, ionosphere, radio wave, blind spot

摘要： 海上安全信息(MSI)对船舶航行安全起到非常重要的作用,航行在宁波-舟山海域的船舶在接收上海海岸电台通过HF NBDP播发的MSI时,经常会遇到通信不良,接收信号很差的情况,尤其在夜晚。就这一现象利用无线电通信的有关知识进行了详细地分析,并在此基础上提出了有效的应对措施来改善接收效果,以期对航行在此海域的船舶在接收MSI时有所帮助。

关键词: 海上安全信息, NBDP, 电离层, 电波, 盲区