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Shortwave radio - Wikipedia
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![Propagation of shortwave/HF radio waves [4] | Download Scientific Diagram](https://www.researchgate.net/profile/Trong-Do-4/publication/322571904/figure/fig2/AS:584134917378048@1516280025015/Propagation-of-shortwave-HF-radio-waves-4.png "Propagation of shortwave/HF radio waves [4] | Download Scientific Diagram")