Short Wave Listening (SWL): Major World Air Route Area (MWARA) I'm located in Florida so most of my listening focuses on the North Atlantic (NAT) portion of the MWARA aeronautical system. These frequencies carry radio traffic between international flights and ground control stations. Modulation / mode: USB NOTE: All frequencies in kHz ===================================================================== NAT-A: Routes between 43N and 47N During OFF-PEAK hours, primary assignment for SOUTHERLY routes New York, Gander, Santa Maria, Shanwick Frequency Notes --------- -------------------------------------- 3016 5598 Very active, last confirmed 2023-04-06 8906 11396 13306 17946 21925 ===================================================================== NAT-B: Routes between 47N and 64N Assignments to aircraft flying EASTBOUND or WESTBOUND tracks Primary for CENTRAL routes Gander, Iceland, Shanwick Frequency Notes --------- -------------------------------------- 2899 5616 Very active, last confirmed 2023-04-06 8864 13291 ===================================================================== NAT-C: Routes between 47N and 64N Assignments to aircraft flying EASTBOUND or WESTBOUND tracks Primary for CENTRAL routes Gander, Iceland, Shanwick Frequency Notes --------- --------------------------------- 2872 5649 Active, last confirmed 2023-04-06 8879 11336 ===================================================================== NAT-D: Routes north of 62N During OFF-PEAK hours, primary assignment for NORTHERLY routes Bodo, Gander, Iceland, Shanwick, Arctic Frequency Notes --------- -------------------------------------- 2971 4675 8891 Very active, lsat confirmed 2023-04-06 13291 ===================================================================== NAT-E: Routes between New York and Santa Maria, south of 43N Unguarded in OFF-PEAK hours New York, Santa Maria Frequency Notes --------- -------------------------------------- 2962 6628 Very active, last confirmed 2023-04-06 8825 11309 13354 17952 21964 ===================================================================== NAT-F: Routes within Gander and Shanwick areas only Gander, Shanwick Frequency Notes --------- ----- 3476 6622 8831 13291 ===================================================================== NAT-H: Routes assigned to aircraft flying entirely within Santa Maria area Santa Maria Frequency Notes --------- ----- 3491 6667 10021 ===================================================================== NAT-I Shanwick Frequency Notes --------- ----- 2890 6595 ===================================================================== NAT-J Shanwick Frequency Notes --------- ----- 3446 6547 ===================================================================== Regional and Domestic Air Route Area (RDARA) Routes over land with no VHF coverage Region 1/1E: 3491 5583 6667 10021 10036 Region 1B: 2890 5484 5568 6550 6595 Region 1D: 2989 5637 Region 10E: 2944 3446 4651 5460 5481 5559 5577 6547 ===================================================================== SELCAL ------ What are these weird tones you're hearing on these frequencies? These are "SELCAL" or "selective calling" tones. These tones encode 4-letter codes that can be used to more-or-less uniquely address one particular aircraft listening on one particular frequency and either activate a notification light or notification chime in the addressed aircraft when received to let the pilots know that a ground station wishes to communicate with them. This is in order to relieve the pilots from having to constantly monitor the voice traffic on these channels, listening for their aircraft's callsign. VOLMET: Weather information for aircraft in-flight -------------------------------------------------- 3413 5540 (?) 5505 8957 13264 Search and Rescue ----------------- 2182 3023 5680 See also -------- https://wiki.radioreference.com/index.php/MWARA https://www.iaa.ie/air-traffic-management/north-atlantic-communications/frequencies https://www.skybrary.aero/articles/selective-calling-system-selcal https://www.icao.int/EURNAT/EUR%20and%20NAT%20Documents/NAT%20Documents/NAT%20Documents/NAT%20Doc%20003/NAT%20Doc003%20-%20HF%20Guidance%20v3.0.0_2015.pdf CREATED 2023-04-06