Also, "falling out of the sky" can still be an effective weapon if you plan for it.
Most of the measures intended to stop access to explosives, weapons and generally dangerous things are not able to do so 100% but simply make the cost of that access high enough MOST malevolent actors will simply not afford it.
GPS is used for all sorts of legitimate human activity, so blocking it would cause problems.
Electronic noise could interfere with not just drones, but all sorts of electronic devices that humans use and need.
Nets, flack, and shotguns could certainly interfere with or harm humans, depending on where they are, and if there's some place they're not to let humans pass, then drones might be able to go through the same route.
Rain is annoying to humans and so plenty of places where humans are are protected against rain, so in those places this is an inadequate defense against drones -- though maybe sprinklers would work (but they can cause their own problems to useful electronics and might even cause an electrocution hazard to humans, depending on where they're used).
In the context of how to respond and if possible disabled a weaponized remote controlled aircraft, I think being dead or seriously wounded also interferes with human activity. These proposals aren't-I didn't get the impression at least-meant to be implemented and operated persistently, but applied into purpose-built apparatuses to disrupt a hostile remote controlled aircraft.
That's a context I'm willing to trade having my phone work for a moment if there's a DJI Phantom dropping bombs over Boston (I beg humor for the hip-hop hyperbole) being taken out of commission before someone gets hurt.
But jamming 1km around every possible target, every day as a precaution is going to be too disruptive. It may actually increase risk to life - by jamming 911 calls for any ordinary accident.
For a spurious one time threat from an unknown actor, then most of these are overkill.
However against a known adversary with an MO for doing drone attacks, these might be legitimate.
An example, a sports event: stringing a fine net from the building/all weather lights, directional GPS blocking (its RF so can trivially be localised.) is cheap and proportional. "RF snipers" with 900 watt converted microwave "guns" (or more likely a beam forming radar type affair)
https://www.youtube.com/watch?v=USYlt9t0lZY
https://arxiv.org/abs/1705.02550
And it's solving a somewhat harder problem - it's done with no maps apart from what it's generating in real time.
Once inertial guidance for missiles became more accurate than ±100 meters, there wasn't a point to reducing the civilian accuracy anymore, so they disabled SA in 2000 and went all-in on availability in 2007.
I know somebody who was having a nuisance/peeping tom issue with a neighbor and a drone. They had an unfortunate accident where their cheapo drone somehow collided with the neighbors.
https://hackaday.com/2011/03/21/herf-gun-zaps-more-than-your...
Scott Evil: Great, now we just need to get the Venezualan President to give a speech at Torrey Pines or the backside of some other world class dynamic soaring hill...
(That's only relevant to this sub-thread's discussion, your point is completely valid in the context of the top level thread... Having said that - needing balloons or planes to get your home-brew autonomous weapons above your target is a whole extra level of logistics and opportunities to get observed/caught compared to launching consumer-grade drones.)
Just don't aim it like a rifle the side lobes might get nasty
900-ish Watts of 2.4GHz will upset most off-the-shelf drones at quite some distance...
1) blocking GPS. 2) Electronic noise (mostly the same as blocking GPS, but needs lots more power) 3) thin nets. (bonus points for barrage balloons) 4) shotguns 5) flak (air burst anti-air shells 6) rain
Off the shelf quadcopters are fragile and not designed to cope with hostile flight. Loose a motor and your falling out of the sky.
Loose a GPS track and you'll either hover, or descend. This could be hacked to rely on dead reckoning, but that's inherently inaccurate. the sensors are designed to tell you what way up you are, how fast you are deviating from desired angle, they rarely have odometers.
A small > 250watt narrow band transmitter, Something with harmonics for 2.4gigs, or just a modified microwave magnetron with a decent directional antenna will destroy most hardware.
A thin fishing net is thin, light, cheap and almost invisible. The hardest part is keeping it in the correct place.