3 ms·

Other links: https://forums.qrz.com/index.php?threads/cuban-government-jamming-40-meter-us-ham-band.772207/ https://forums.qrz.com/index.php?threads/cuban-gove

Other links: https://forums.qrz.com/index.php?threads/cuban-government-jamming-40-meter-us-ham-band.772207/ https://forums.qrz.com/index.php?threads/cuban-government-ja... https://k0lwc.com/direction-finding-points-to-cuba-jamming-ham-radio-frequencies/ https://k0lwc.com/direction-finding-points-to-cuba-jamming-h... https://www.youtube.com/watch?v=gVJS4skdtR8 https://www.youtube.com/watch?v=gVJS4skdtR8 https://www.youtube.com/watch?v=dtICIDDvnPw https://www.youtube.com/watch?v=dtICIDDvnPw

JoeDaDude 5y ago
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-ham-radio-frequencies/ https://k0lwc.com/direction-finding-points-to-cuba-jamming-h...
- user3939382 5y ago
  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.html https://wfebb101.com/faq/how-to-triangulate-a-radio-signal.h...
- mindcrime 5y ago
  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
- nvahalik 5y ago
  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.
  - lightlyused 5y ago
    None of the SDRs in the videos have directional antennas, so my trust of the results is low.
motohagiography 5y ago
Watched the youtube video and it was followed by another one about direction finding using KiwiSDR - which yielded a recent story about how that SDR had been backdoored: https://arstechnica.com/gadgets/2021/07/for-years-a-backdoor-in-popular-kiwisdr-product-gave-root-to-project-developer/ https://arstechnica.com/gadgets/2021/07/for-years-a-backdoor... Is it just me or does anything to do with RF and hardware seem like spy games all the way down?
- reedjosh 5y ago
  I think anything communications related is spy games all the way down.
- BuildTheRobots 5y ago
  The kiwiSDR news was posted yesterday, but has very few votes. I could have expected it to gain more interest. https://news.ycombinator.com/item?id=27849008 https://news.ycombinator.com/item?id=27849008

JoeDaDude 5y ago

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-ham-radio-frequencies/ https://k0lwc.com/direction-finding-points-to-cuba-jamming-h...

user3939382 5y ago
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.html https://wfebb101.com/faq/how-to-triangulate-a-radio-signal.h...
mindcrime 5y ago
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
nvahalik 5y ago
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.
- lightlyused 5y ago
  None of the SDRs in the videos have directional antennas, so my trust of the results is low.

motohagiography 5y ago

Watched the youtube video and it was followed by another one about direction finding using KiwiSDR - which yielded a recent story about how that SDR had been backdoored: https://arstechnica.com/gadgets/2021/07/for-years-a-backdoor-in-popular-kiwisdr-product-gave-root-to-project-developer/ https://arstechnica.com/gadgets/2021/07/for-years-a-backdoor... Is it just me or does anything to do with RF and hardware seem like spy games all the way down?

reedjosh 5y ago
I think anything communications related is spy games all the way down.
BuildTheRobots 5y ago
The kiwiSDR news was posted yesterday, but has very few votes. I could have expected it to gain more interest. https://news.ycombinator.com/item?id=27849008 https://news.ycombinator.com/item?id=27849008