Which method provides the best indication for a GMDSS Radio Operator about establishing ARQ communication with a coast radio station?

The best indication for a GMDSS Radio Operator about establishing ARQ (Automatic Repeat reQuest) communication with a coast radio station is found in monitoring the coast radio station's "free signals." These signals, also known as "pre-signals," serve as notifications that a radio station is ready and available for communication. By listening for these signals, the operator can confirm that the coast station is operational and thus can increase the likelihood of successfully establishing a two-way communication link.

This method allows the operator to assess real-time conditions and availability, providing an efficient way to determine the operational status of the coast station. Engaging with free signals can also provide insights into the potential success of ARQ communications, which rely on a stable net link for sending and confirming messages effectively.

In contrast, using propagation charts can help anticipate the best frequencies based on atmospheric conditions, but it does not provide immediate feedback on the specific readiness or availability of a station at that moment. Selecting a frequency in the MF band is critical for communication but doesn't guarantee that the coast station is available or listening on that frequency. Lastly, re-positioning the antenna and pressing the "call request" button will not yield information regarding the operational status or readiness of the coast station without first confirming through