Hacker News Reader

Comment by M_Grey | Hacker News Reader

Or, "How to kill people with pacemakers". Seriously, there are a lot of bad uses for this which have nothing to do with phones.

View on HN

This is being operated at distances where you could just as easily hit the device directly with a hammer. To scale the distance up to just a couple of meters (say about 50 times the distance), you'd need to scale up the power by about 50*50 = 2500 times.

I suppose it is conceivable that a suitcase-sized device could disrupt the actions of pacemakers of people walking within a meter or two. But it could just as well cause trouble with much more conventional means.

Actually even more since some near-field components fall off at 1/r^3.

Correct me if I'm wrong: the near fields don't take out any energy if nothing's coupling to them. They're like a reactive load. The far fields, however, take energy out to infinity regardless of what's out there.

Yep, correct. I posted a link in another comment, but this is a good picture of all the components for small dipoles and loops.

http://www.rfcafe.com/references/electrical/near-far-field.h...

Quick question: if you put a sink in the far field, does that increase energy drain at the source, or is the definition of the far field such that the field strength around the vicinity of the sink is the only thing practically affected?

No additional energy drain. In fact, one of the definitions of far field is that any thing in it can't change the impedance of the radiating antenna. There is a good article in this months IEEE APS magazine exploring where the far field begins. Coincidence I was reading it last night.

Would those means leave a more obvious forensic trace? I mean... a hammer is going to leave a mark.

There's probably a fairly large set of people who would never consider hitting someone in the chest with a hammer, but would fire up a device like this for the lulz, not knowing that someone with a pacemaker was within range.

Dick Cheney has several vulnerabilities, besides disabled telemetry.

Or one of those going off on a plane. Horrible consequences.

Oh damn it... that's a good point. What would the effect be if you got one into a critical part of a power or transmission station too? Not good I bet.

Knock out a city block or worse.

Not a great deal tbh.

Inverse square law means it'll have bugger all range and those kinds of systems are large enough with enough 'capacity' to just soak it up.

Next to the control computer maybe but not in a transmission station.

Then you could just as well bring a crowbar and throw it at something to cause a short. Or just smash stuff manually. This device has a very small range.

Sure, but then someone finds a crowbar, or smashed stuff... what obvious trace would this leave, and could it be scaled up?

Shortcircuit something that transfers couple of gigawatts with a crowbar and you will have molten crowbar puddle at the end. Or vaporized.

A puddle of crowbar is still going to be forensically valuable, and a lot easier to find than for example, bomb fragments.

You would not be able to take this into a plane, but good thought.

You'd need a lot more current in order to cause horrible consequences for an airplane. Lots of redundant systems, lots of testing for electromagnetic tolerance.

I really hope so. I love to travel.

This is what a setup for testing airplanes for EMP tolerance looks like: https://en.wikipedia.org/wiki/ATLAS-I Note that this isn't used anymore.

And here's an anechoic chamber for testing military craft: https://en.wikipedia.org/wiki/Benefield_Anechoic_Facility

Now I'm curious to see an A380 in an anechoic chamber... Are full airplanes normally tested in a chamber? Or only the individual systems?

Why do you need a chamber?

Fully anechoic chambers are for antenna pattern testing and scenario testing where you don't want reflections; you want to simulate free space such as planes in the air.

Semi-anechoic is for electromagnetic compliance testing. They have absorber on walls but not floor. Typically don't want signals to get out. Bare floor sort of mimics earth, as ground plane can guide wave.

Some chambers are fully reflective with mode stirrers, but those are specifically for EM susceptibility testing.

Both

I don't think they're gonna let you take your emp device on board

Oh, please. An induction coil charger probably emits more power.

In addition, this emits a VERY wide bandwidth noise pulse (look at the frequency output of a spark gap transmitter) which of necessity puts very little power in any specific band.

Reply on news.ycombinator.com