What about drones with GPS and preplanned flight paths?
Great idea BUT could this be used in the future to wreck self driving vehicles or hijack delivery drones??? This thing could be more dangerous than a real gun. I could see a larger version of this taking down aircraft or wreaking havoc on an expressway where every car is controlled with a computer. While this may not yet be a powerful EMP weapon, it's just a matter of scale.
I think the FCC also has some problems with this device. Besides almost certainly exceeding the radiated power limits for an unlicensed device and the FCC prohibiting civilian jammers generally, it is probably unsafe to have a high-output antenna that close to your face for minutes on end, even though nearly all the power is going forward - the near field has higher field strengths than one would expect from looking at the emissions from a distance. They should put a copper mesh groundplane a couple of feet across between the antenna and the operator. Painted black with a transparent conductive-coated aperture for the scope, the mesh would still allow sighting but greatly reduce cooking the operator's eyeballs.
GPS jammers are also potentially dangerous to aircraft, especially those coming in for a landing, certainly more of a threat than most handheld lasers. I expect these drone-jamming devices will not be licensed for civilian use.
This is utterly ridiculous - we already have nutcases irritating planes with later pointers, and now you want to give people the ability to totally disable their GPS and navigation? And for what? Anything that this might possibly protect against, needs only one tiny software upgrade to convert it into a suicide device: if(I_am_being_jammed){follow_signal; self-destruct-on-impact}... the nutcase with the jammer becomes the beacon the drone needs to head for to destroy the jamming device and/or operator.
Stephen N Russell
Used similar device but larger in 50s movie Earth vs Flying Saucers to defeat UFOs over Wash DC ( on DVD).
If it's actually a "drone" eg. autopiloted not four motors and it flies, I don't see why an autopilot doesn't take over and keep it in the air using accelerometers/gyro and head back to where it came from unless GPS is gone too. Didn't read article though <- dumb

This guy's pointinga helical antenna like a gun lol.
But will it work against the Predator?
Mel Tisdale
For some people, the fact that it is illegal is immaterial.
How long will it take for autonomous vehicle projects to be abandoned on the basis that they have too many vulnerabilities?
I'm sure that people that want to breach that fence are smart enough to have more than 1 drone. I would think that the price of these things is in the area of thousands of dollars and there is only one per institution, while the price of drones is in the low hundreds of dollars. If I'm sneaking a cell phone into a prison, and even if I lose 2 to 1, Jimmy the Shank gets his cell phone.
There are UAVs that can navigate from an initial GPS co-ordinate using fairly sophisticated 6 axis gyros and accelerometers with high levels of accuracy (in fact some mini quads use them and forgo GPS entirely). So if such a UAV is flying a preprogrammed path, with timed "actions" commands using something like the Arduino, then cutting it off from outside radio commands or it's GPS reception is going to achieve nothing.
If I was seriously going to use a UAV as a weapon then I'd put a number of 3KG lift hexcopters over my target at 1000m+, where they would not be seen or heard (without artificial aids), and have them release a dozen or so 250 gram fletchets. These would hit the ground with about the same force as a burst from a .50cal machine gun. This "Dronedefender" would in all likelihood be out of range, and the operator will not have seen the threat.