I have read a few articles about the hyper-competitve world of high-frequency trading (HFT), and how a few milliseconds of network latency might cost millions of dollars.
Apparently some of these enterprising traders have gone off and setup some rather sophisticated HF data links to bypass the whole Internet and flash their trades from here to Europe on HF.
I don’t know that this signal, that I’ve seen multiple times just above the 17 meter amateur radio band (and also above the 20 meter band), is one of these traders or not, but it’s a remarkable signal considering that it is almost 50 kHz wide and quite strong. I would guess that the transmitter power is in the range of 10 to 50 kilowatts to produce this kind of signal.