Comes on air every evening at 2300UTC and off air at 2400 UTC. The two frequencies where this signal is heard are always 282 kHz apart. Heard on numerous EastCoast USA WebSDR receivers, although the farther north from Florida you get the weaker the signal is. Unable to hear on any South America WebSDR, as most of them are too far south. The attached recording was taken with LSB, bandwidth on receiver is 2.5 kHz.
I/Q Raw Recording
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Audio Sample
This sounds either like a very wide and fast CODAR, or some type of radar/sonde scanning the airwaves at a constant 250 millisecs.