Actually, it might be the good old shortwave radio: https://spectrum.ieee.org/tech-talk/telecom/wireless/wall-street-tries-shortwave-radio-to-make-highfrequency

Actually, it might be the good old shortwave radio: https://spectrum.ieee.org/tech-talk/telecom/wireless/wall-street-tries-shortwave-radio-to-make-highfrequency-trades-across-the-atlantic https://spectrum.ieee.org/tech-talk/telecom/wireless/wall-st...