Check Out This Free Document
Monitoring Transatlantic HF
If you are interested in listening to the birds on HF, then the document Communication Services (AIRAC Amdt 001/20, GEN 3.4.1., 30th January 2020) by the Irish Aviation Authority is well worth a browse. It contains details on, among other things, Aeronautical Communication Services in the SHANWICK Oceanic Control Area of the ICAO North Atlantic Region. These are provided, through international agreement, by SHANWICK Aeradio, an aeronautical communications facility, operated by the Irish Aviation Authority. Radio frequencies, hours of operation and types of service are all covered, as are message types, the meaning of emergency messages, and much else besides.
(Source: Shanwick Oceanic Radio Facebook Group, IAA)