How to Make a Handheld EMP Jammer | Hacker News Reader

How to Make a Handheld EMP Jammer

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134 pointsadius93 comments

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

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.

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.

This won't destroy your phone. Phones are extensively tested when it comes to both creating and withstanding EM interference. Best it could do - maybe - is crash one that is on the edge of its spec and you would probably have to get pretty close for that (fall off as the square (edited) of the distance).

How about something like an Explosively pumped flux compression generator, I'm thinking there must be bits of EEPROM or equivalent in the phone that hold important info like the imei number, that if damaged, would render it unusable?

I'll upvote the article if you build and test it :) (On your phone, in your lab).

That has a chance of working due the very fast rise time you might be able to induce a sufficiently large voltage to cause some actual damage, it will be a 'one shot' affair though. But anything involving regular coils and some push button arrangement will likely cause it's own insulation to break down long before it will do damage to a phone.

That's one of the reasons the spark gap is there in the first place, without it you'd hit the limits of the coil insulation very quickly.

Spark gaps are a pretty nasty way to generate EM interference so there is some truth to the story.

But even with my plasma cutter (12.5 KW, so not the smallest in the catalog) and stick welder I never managed to crash a cell phone.

The plasmacutter did have the habit of resetting the controller until I properly decoupled all the lines into it.

If only I had such a lab :)

That's really interesting with respect to your plasma cutter.

Nasty little toy. Don't point it at anything you want to keep.

A friend of mine did some back of the envelope calculations at Burningman one year when the megaphone guys were being particularly annoying - he came up with (from memory) 1km of fine copper wire wrapped round 100g of plastic explosive in the right configuration would probably let you take out a typical megaphone at 20m...

(Note: all memories and calculations are from Burningman a decade or so back - and should be treated with an entire playa-ful of grains of salt.)

Give me the 100g of plastic explosives, and I could take out the megaphone without needing the copper wire. (Though it might be a bit rough on the megaphone operator. On the other hand, that copper wire is going to create some pretty nasty shrapnel...)

Well yeah - nobody ever said it was gonna be a good idea ;-)

(This was the same crew of people where the discussion one night went "We're all on mushrooms, you've just been drinking tequila all night - that means you get to fix the flamethrower"...)

That quote just went into my permanent database...

"People will say it's a booooomb..." to the tune of People Will Say We're in Love

Seriously though... can you imagine how many laws you'd break using that? The FBI would hang you up by your pubic hair, tar, and feather you.

Only if you do it in US.

Where could you do it that wouldn't take it badly?

Shouldn't the signal fall off with the square of the distance (inverse-square law)?

Yes.

Yes, apologies.

aiui.

its not linear.

either it induces a voltage high enough to cause disruption or it doesnt.

the limiting factor is the voltage not the power (power is tiny)

and what i mean by that, is we are talking about a pulse of high voltage and very very high frequency (maybe even gamma radiation) and its effect on electronics.

thats not a case of power falloff. Because interaction with the environment and target is non linear.

for example if it blasts a phone to reset from a few centimeters it could easily drop all calls in a 20 meter radius. but upping the power/voltage 4 times may only add milimeters to the range of blasting the phone to reset because so much is absorbed by the case. but upping the power/voltage 5 times could add a meter to blasting the phone to reset because the case now no longer absorbs enough energy to prevent the interference. Also resonance and harmonics play a huge role in the effect.

All conjecture. but my point is you cant apply school boy physics to the problem because its not a problem they teach in school.

There's a very big difference between EM interference and an EM pulse. One is the by-product of all digital electronics and one is a device specifically designed to induce enough current on a circuit board/IC/etc to damage it.

That said, based on the size of that thing in the photo I suspect it wouldn't damage anything!

The biggest difference is the fieldstrength of the primary field used to induce a voltage in the target, the same basic principles apply.

It takes a (much) higher fieldstrength to induce voltages that will destroy electronics than what's required to flip the occasional bit without damage.

Lightning can cause EMP like effects by inducing voltage in conductors not directly hit by the lightning.

I vividly remember riding a motorcycle next to a lake, when a lightning strike hit the lake maybe 20-30m from where I was. The bike's engine died briefly (maybe 0.5 or 1 sec) then came good again - I'm pretty sure it was the fairly simple electronics driving the ignition getting "zapped".

(This was a 1991-vintage bike - its modern enough that it uses hall sensors not points, but the electronics driving the ignition and the advance curves might even be analog instead of microcontroller-driven.)

Would it disable an annoying car alarm?

Or stereo or subwoofer? I find that an interesting concept.

For stereos, use an AM transmitter and send your neighbor dora-the-explorer theme music on repeat.

Good idea. Too many are using MP3 or streaming now, though. We need something for that.

A focused AM transmitter will send it directly to the speakers.

When you're close enough to the towers, you can hear the transmissions on leaves.

Leaves? Hows that work? Ive seen a person do it with jumper cables but do you have a video of that?

Note: I also have a new theory behind schizophrenia diagnoses about trees talking to people.

Best I could do put on the spot: http://www.dailymail.co.uk/sciencetech/article-3276974/Incre...

It's actually touching the tower though.

(and I have no idea how it works)

I thought you meant plants nearby. Ive seen that trick. Same as jumper cables. What the latter appeared to do what (a) get conductor close enought to it for spark to jump, (b) spark superheats/vibrates the air in way corresponding to waves its carrying, and (c) those sound waves reach your ear. This is what I gathered as someone without RF training but knowing how sound usually forms.

Can am AM transmitter be made directional though? Otherwise the power would be forbidding, and the collateral damage would be worse than the cause.

Sure it can. Phased shifted arrays of monopole antennas are often used to steer broadcast signals in a particular direction (If you've ever seen a group of 2-3 radio towers sitting close together in the country side, that's what they're doing).

That said: if you're in the US and transmit outside of the ISM bands or at anything above about a few hundred milliwatts of power, you risk the FCC coming down on you with some hefty fines or jail time.

AM is used to describe a frequency range here (the 'AM Band'), but it is actually referring to 'Amplitude Modulation', a way to superimpose the signal on the carrier wave. You can do 'AM' at any frequency and your ability to direct the radio waves goes up as the frequency goes up. AM transmitters at the frequencies associated with the AM band (550-1600 KHz) can be directional, in fact, every antenna is more or less directional.

What makes it tricky is that at those low frequencies the antenna elements are very large, and this is what will play havoc with any attempts to make a directional antenna for the AM Band that is still practical to use for the purpose described here.

So in all likelihood you'll end up upsetting all your neighbors instead of just the one you're targeting.

Yes, or the entire car: https://www.youtube.com/watch?v=cuus8OtPY0w

Vehicle disabling EMPs are of great interest to the likes of CHP, and such.

That would probably be completely ineffective on something like an old-school fully-mechanical diesel, which will run as long as there's fuel and air. I suspect a lot of military vehicles use those for the same EMP-proofing reason.

Just to clarify after seeing several posts below. The magnetic and electric near fields fall off from 1/r^3 to 1/r^2, depending on component. The far fields fall off at 1/r, hence the familiar 1/r^2 for power (not amplitude).

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

This thing operates in the near field, so it is pretty much useless past a distance of a coil diameter.

If you wanted to do this right, you'd match the impedance to the antennae impedance of a typical phone antennae.

This gets around the square rule, sort of, and you won't need a suitcase full of batteries to power the thing.

Things like that were used to cheat slot machines http://empjammer.com/how-a-emp-jammer-working

Much cheaper to use an electric gas lighter.

That's what we used to test on stuff that was supposed to be reliable and it is amazing how hard it is to defend against it. If you could survive 10 seconds or more without a latch losing state or some other bitflip then it was usually a pretty good job. Even so, this required physical contact to something made of metal on the machine (even if most of it is properly grounded there always is some exposed metal that isn't).

I hope the engineering on that product is better than the English, it is barely understandable.

Heh - showing my age here, but I remember using gas lighters (stolen from school heaters) to zap free game credits into Asteroids machines...

Same. And pinball machines and others.

Feel pretty bad about it now, because I probably destroyed a few IC boards.

What did you do? Just heat it up till it does "something"?

Just zap some of the metal around the coin slot until it either crashed or gave you free games.

(These were the piezo spark-ignitors, not pilot flames...)

Thanks for reminding it to me , i've been sent out from some arcades for doing it, and the owner of the arcade hearing the clicks.

ESD is not EMP.

Here's the Nevada Gaming Commission's answer to that.[1] More stuff should have security standards like this.

[1] http://gaming.nv.gov/modules/showdocument.aspx?documentid=29...

I've often thought about using a wok as a dish and putting a magnetron at the focus. High power directed microwaves would probably damage a lot of things. And made from kitchen hardware...

Probably safer to let somebody else try this... ;) A couple of Ukrainians made a cool YouTube video recently where they built something similar and used it to blow up some cell phones. https://www.youtube.com/watch?v=FIU8WZR9DNA

I think they've been using it on Samsung Note 7s more recently.

You really don't want to microwave a Lithium-Ion battery.

Oh yeah I do!

(From a distance. With a camera running...)

(It can't be much worse than all the times I've smashed LiPo batteries into the ground (or a tree or another quad) at 80+mph... They only _rarely_ "vigorously discharge" as a result of that. I'm pretty careful the next few times I recharge one after a particularly violent crash...)

They seem to have absolutely no sense of self preservation.

Can they really expose their hand to that (below the temperate at which they get a burn) with no internal/hidden damage whatsoever?

It's not ionizing radiation, so the only damage is from the heat. So they probably can expose their hand without damage.

Just because it's non-ionizing doesn't mean it's safe. HERF will simply cook you, and just like your kitchen microwave oven it will cook the strongest at the antinodes. This means you can get very nasty burns inside your hand that don't show on the surface.

Just being near some antennas when it is transmitting can give you a very nasty RF burn. A magnetron that can damage electronics (or cause almost any visible effect) is going to do you what it does to your food.

Seriously, don't mess with high-energy RF without proper safety training. Waving around an open magnetron that could be reflecting back at you in unknown ways is incredibly dangerous.

Up the comment chain here it shows that these nutters are living in an active war zone, so safety is a relative idea when your home is being shelled by the 20th Army of the Ground Forces of the Russian Federation.

The video is lovely (and now I absolutely want to try it at home!). That said, the ending disturbed me. As I understood, it basically said - "don't worry, none of our neighbours suffered, because they all moved out when the war started".

EDIT:

Holy shit, they have a video of what's left of their town after shelling stopped: https://www.youtube.com/watch?v=v4mc5mHksl8.

This seems like a device that is possible to cause a lithium battery fire because of the discharge rate.

What component is failing in order to cause that iphone's screen to fade out in that way?

Why a second external coil? It isn't aligned with the first coil and so the induced EMF is minimized (usually such coils are co-axial).

It doesn't destroy phones, though. It resets them at max according to the video and tests.

Funny he can build an EMP generator but can't properly bias an LED.

this reminds me of a coworker who tried to create a tiny DC motor with a battery, a magnet, and _non-enameled_ wire. yeah, that didn't work out too well for him. I tried to explain why the wire needed to be enameled, but the cargo-cult science was strong with him.

How would the design need to be changed to make it possible to zap a phone from a distance of 1-10 meters?

You need 1.21 Gigawatts for that.

(Seriously, though, you'll need to square the power source as you double the distance.)

Does that mean the rest of the system can stay the same? Aassuming minimal adjustments required to wire gauge as power increases.

Sweet! ... My EMP generator only works on Samsung Galaxy Note 7s!

"18650 lithium battery cell"

Or, possibly, explode into flaming death.

Ok, so let me put it another way: how much resistance does that circuit have?

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