Radio direction finding[1] can be complicated in a "the devil is in the details" sense, but the basics are fairly simple. All you really need are two stations w

Radio direction finding[1] can be complicated in a "the devil is in the details" sense, but the basics are fairly simple. All you really need are two stations with directional antennas[2] which can be reoriented freely. You have both stations reorient their antennas until they see maximum signal strength from the signal in question. Now you have two points at known, fixed locations, along with two angles - from there it's straightforward triangulation[3]. Using more stations can help reduce the error and get a more precise fix on the source of the transmission. That said, again, "the devil is in the details" because of things like ionospheric reflection, attenuation from passing through things, etc. Radio signals usually travel in approximately straight lines, but there are some quirks that come into play, depending on the frequencies involved, distances, and suchlike. See also: Radio Direction Finder (RDF)[4] [1]: https://en.wikipedia.org/wiki/Direction_finding https://en.wikipedia.org/wiki/Direction_finding [2]: https://en.wikipedia.org/wiki/Directional_antenna https://en.wikipedia.org/wiki/Directional_antenna [3]: https://en.wikipedia.org/wiki/Triangulation https://en.wikipedia.org/wiki/Triangulation [4]: https://en.wikipedia.org/wiki/Radio_direction_finder https://en.wikipedia.org/wiki/Radio_direction_finder