On the defensive side, see perhaps this phased array radar system with a 20km range:
* https://github.com/NawfalMotii79/PLFM_RADAR
Expanding on that, for interest:
* https://en.wikipedia.org/wiki/Phased_array
* https://www.globenewswire.com/news-release/2003/02/11/294058...
* https://en.wikipedia.org/wiki/Multi-role_Electronically_Scan...
* https://en.wikipedia.org/wiki/Boeing_E-7_Wedgetail
What a time to be alive.
In fact, I think I now have all I need to start a war with my neighbours.
How is DIY radar regulated by the FCC?
Expanding on that, for interest:
* https://en.wikipedia.org/wiki/Phased_array
* https://www.globenewswire.com/news-release/2003/02/11/294058...
* https://en.wikipedia.org/wiki/Multi-role_Electronically_Scan...
* https://en.wikipedia.org/wiki/Boeing_E-7_Wedgetail