>low-cost ADALM-Pluto
~$250, meanwhile Chinese nanoVNA clones are ~$25-40, add prescaler and you can reach 6GHz.
Anecdotally I have seen nanoVNAs being used with directional antennas in Ukraine as crude drone finders. https://www.reddit.com/r/CombatFootage/comments/1afspa8/comb...