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Comment by JoeDaDude | Hacker News Reader

Interesting maps on [0], though details on how direction finding was done are lacking. Is this something anyone can do with friends who have radios around the country? If so, how?

[0] https://k0lwc.com/direction-finding-points-to-cuba-jamming-h...

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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

[2]: https://en.wikipedia.org/wiki/Directional_antenna

[3]: https://en.wikipedia.org/wiki/Triangulation

[4]: https://en.wikipedia.org/wiki/Radio_direction_finder

Signal triangulation. You compare strength of a broadcast from a few locations to deduce broadcast location. In the US there’s a volunteer group that does this for the FCC, I forget the name.

https://wfebb101.com/faq/how-to-triangulate-a-radio-signal.h...

Direction finding is usually done with antennas which have large null regions. (Highly directional). You point them in a direction and if you get a signal you mark that down.

Then just repeat 3+ more times.

None of the SDRs in the videos have directional antennas, so my trust of the results is low.

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