How can a GMDSS operator determine the best frequency band for a SITOR transmission?

To determine the best frequency band for a SITOR (Simplex Telex Over Radio) transmission, listening to shore station "free signals" provides valuable real-time information. By monitoring which band has the strongest signal from a shore station, the operator can make an informed choice about which frequency is currently optimal for transmission. This approach takes into account current propagation conditions, which can vary due to factors like time of day, atmospheric conditions, and seasonal changes.

The strategy of utilizing real-time signals is particularly effective because it directly measures how the signal behaves in the current environment, as opposed to relying solely on theoretical models or historical data. Additionally, this method helps ensure that the operator is choosing a frequency that is less likely to be congested or experiencing interference, which is essential for successful communication.

Other approaches, while they may hold validity in different contexts, do not provide the same immediate feedback as monitoring live signals. For example, consulting propagation tables can provide general guidance based on expected conditions but may not accurately reflect the moment-to-moment variability of radio wave propagation. The suggestion to try lower bands if static interference is present is useful but does not consider the current availability of channels with less activity. Lastly, the idea of choosing higher frequencies at night and lower frequencies