This is one frequency in the US Air Force maintained HF-GCS network. More than jsut the US Air Force uses this network, but they op / maintain it. Many, many, messages a day will be heard on the common freqs, 4724, 6739, 8992, 11175, 13200, and 15016 kHz. Often messages are simulcast on more than one frequency at a time, so that all freqs might be carrying the same traffic.
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