What means are used to prevent the reception of unwanted broadcasts by vessels utilizing the NAVTEX system?

The NAVTEX system is designed to provide maritime navigational and safety information, and having the ability to prevent the reception of unwanted broadcasts is crucial for maintaining effective communication and navigation. Programming the receiver to reject unwanted broadcasts is the most effective method because it allows vessels to filter out signals that are not relevant to their current needs or operations. This selective reception ensures that the crew can focus on the information that is pertinent to their voyage, thus avoiding confusion and potential safety risks associated with receiving irrelevant communications.

On the other hand, methods such as operating the receiver only during daytime hours or coordinating reception with broadcast schedules do not actively prevent unwanted broadcasts; they merely limit when or how broadcasts are received. Similarly, automatic receiver de-sensitization during night hours would not specifically target unwanted broadcasts and might reduce overall sensitivity during times when important information is still being transmitted, making these alternatives less effective than programming the receiver directly to filter out undesired signals.