HERF Gun Zaps More Than Your Dinner


Instructables user [Jimmy Neutron] had an old microwave sitting around and figured he might as well gut it to build a high-energy radio frequency (HERF) gun.

The concept of a HERF gun is not incredibly complex. Much like your microwave at home functions, a high voltage power source is used to drive a magnetron, which produces micro wave radiation at 2.45GHz. These waves are then guided away from the magnetron using a waveguide, towards whatever the target might be. These waves then energize the target in a similar fashion as the water molecules in your food are energized during cooking.

[Jimmy] has not quite finished his HERF gun as he still needs to build a waveguide for it and then safely mount it for use. In the meantime, check out the pair of HERF guns we found in the videos below.

As a parting note, we must stress that building a similar device is dangerous, very dangerous – especially if you do not know what you are doing. Microwaves contain high voltage components, and exposure to microwave radiation can be deadly under certain circumstances. Stay safe!

Looking for more microwave fun? Check these out!



76 thoughts on “HERF Gun Zaps More Than Your Dinner

    1. Actually as stated in the Instructables version by someone with proper testing equipment, without the directional antenna a 600w magnetron isn’t really dangerous…I tried frying a possum with one at 10ft from a 1000w magnetron and it did nothing…though mine didn’t have a wave guide so that may have been the issue…

    2. The risk of other types of thermal injury only really exists if you are within a metre or so of an unshielded kW magnetron (inverse square etc.) so if you’re not a complete imbecile messing around with microwaves isn’t that dangerous.

      The greatest risk is blindness, but as Wikipedia says: “Microwave-induced cataracts are reported in scattered and isolated partially documented cases, but these are insufficient for establishing a causal relationship of higher than only conjectural validity; while it is possible to cause a cataract by exposure to microwaves, the required intensities WOULD CAUSE BRAIN DEATH. Experiments on rabbits and dogs, mostly in the UHF range of frequencies, shown that the ocular effects are confined to eyelids and conjuctiva (as e.g. anterior segment keratitis or iritis).[7] Cataracts were observed at several workers exposed to radiofrequency radiation, but in some of the cases the cause was unrelated to the RF exposure and in the other cases the evidence was incomplete or inconclusive.”

      The main risks to your health are the RF police and the high voltage supply, but there are thousands of ‘how-to’s for those around here that I don’t see you complaining about :)

      1. As a former General class amateur radio operator (at the young age of 13 some years ago), I would confirm that this device, if not properly shielded, grounded, and wired, can pose a serious danger to a novice. Microwave induced cataracts and ocular opacities have been reportedly suffered by technicians who worked with microwave and radar systems in the scientific literature. Without a highly directional resonant waveguide, the power density follows the inverse square law in its dissipation from the source. With a highly directional waveguide, there is still the danger of more concentrated thermal injury to human skin at close distances from the source of emission.
        Chemical leakages from the magnetron may also pose a neurological danger if aerosolized and inhaled.
        Unless proper safeguards are taken with respect to any rewiring of the device, high voltage danger exists to those unfamiliar with uhf and microwave electronics.

    1. In the first video there was a waveguide for the magnetron which is dangerous but within the realm of reasonable. However in the second video there was just the emitter probe .
      I mean that’s just plain crazy. The microwaves will radiate in all directions and can cause serious radio frequency burns.

  1. You forgot the legal police.

    This is also very illegal. Microwaves generally use the ISM band centered around 2.4ghz. They are only legally operating at 1kW because the radiated power (outside of the enclosure) must be below 5mW. By only removing the magnetron you blow that out of the water, and by focusing it you enter crazy-town. I hope this person gives themselves radio burns and destroys is before anyone else gets hurt.

  2. I have to agree with HackerK: It’s one thing if some people are stupid enough to play around with magnetron. You can’t prevent that. It’s another thing to promote this. Using these to make “guns” isn’t “dangerous, very dangerous”, this is simply dumb.

  3. @hpux735 – you truly wish physical harm on this kid because he’s doing something you don’t agree with? C’mon, pull your panties out of your crack.

    Is it stupid? Yes. Is it dangerous? Yes. Is it impacting you? Not so much.

    @hubert – The dude in the second video is totally wearing a foil crotch protector – it’s all good!

  4. This is a cool hack. Incredibly dangerous, but very awesome.

    Don’t aim it at any large objects, i.e. sheets of metal, concrete walls, etc.

    Some of the radio waves will be reflected, unpredictably cooking other stuff nearby.

  5. I read in QST about 20 years ago a letter from a ham who blinded himself with high power UHF. He got the dose before he knew he was injured. Apparently the retina is pretty sensitive to being damaged this way.
    I agree with others that it’s just not smart.Bruce Perens K6BP

  6. This is as easy as pulling apart an old microwave and mounting the magnetron on a satellite dish. I didn’t know that was all it took to get on HaD.

    Also, the real safety danger is your eyes. While the rest of your body would take a few minutes to be significantly damaged, eyes will turn white like a poached egg in 15-30 seconds.

  7. @hpux735 –

    “I hope this person gives themselves radio burns and destroys is before anyone else gets hurt.”

    Typos aside, looks like a clear desire to see this person injured as a result of their tomfoolery regardless of your concern for others.

    As long as this kid does not stand in front of the magnetron, point it at another living thing, or stick the beryllium in his mouth this is no more dangerous than building a tesla coil. At least he might get a bit of a burning sensation if he accidentally steps in the way of the micro waves – 10kv doesn’t stop to say hello before striking you dead.

    At the end of the day if his parents are letting him screw with these things or his “uncle” is not supervising him while experimenting, they are ultimately at fault if something goes wrong.

  8. really what is shown here is the inside of a microwave, assembled outside of the box. so, i could take the case off my VCR, NES, cellphone, tv, etc.. and call it a hack, except those things wont cause bodily harm at long range..

  9. Very cool to see this type of project here!

    If this kind of thing interests anyone I suggest checking out the boards at 4hv.org for other awesome and dangerous projects without many comments from concerned mothers. ;)

    1. concerned mothers,lol….best comment on this page by far…though i do agree this is pretty stupid shit to be fuckin around with … 2000V alone in my opinioin is outrageous to just have placed on a piece of plpywood lol

  10. @SamIAm

    I’ll grant you that I wasn’t as clear as I could be, and I want to emphasize that I DO NOT want ANYONE to get hurt.

    Anyway, once you feel a bit of a “burning sensation” the damage has been done. There are many examples of significant and permanent damage occurred hours (or days) after exposure. Just lookup “microwave burns”.

    In my opinion this is no better than making pipe bombs. There are just as many reasonable uses, and just as many dangers.

    1. Actually, with proper safety and blah blah blah, I’d really like to see this done! See if two phones can pair over 50 miles! Can you frequency-modulate a magnetron?

  11. Nice thing. (Also nice how it got the Wussy Brigade buzzing.)

    Could be used as a wide-area wifi/bluetooth jammer. Or a long-range one, with a good directional antenna.

    Given the magnetron radiates more or less omnidirectionally from its tip, the EM field intensity drops pretty fast with distance. With precautions it should not be That Much Dangerous, though it is definitely something to pay attention to while playing with it.

    I wonder… if the signal is modulated, could it be used for moon bounce communication? Alternatively, could it be just keyed on/off and use a suitable receiver nearby to have a radar bounde from the Moon?

    An interesting thing to do is melting glass with microwaves. The trick is to focus the power into a small area in the glass mass; once it heats enough, it starts absorbing enough to be heated efficiently.

    Another possible thing to have fun with is trying to tune the magnetron, how much of frequency shift could be achieved. Also, power modulation is of interest. (See “microwave-assisted chemistry” for more ideas for its use. Also microwave-assisted drying of materials.)

  12. Looks like fun! everyone yelling, just shut up and don’t play with these kind of things if you don’t want to.

    Reasonable people adapt themselves to the world. Unreasonable people attempt to adapt the world to themselves. All progress, therefore, depends on unreasonable people.

  13. What, not even portable? Hardly a HERF gun.

    I did look into this a while back for powering a plasma experiment.. turns out that you can drive a magnetron using the inverter transformers from a 32″ or larger LCD but it needs to be the sort with two large transformers and not the eight small ones.
    Run them in parallel with diodes to rectify the HV and a smaller winding wound around one or both and it should power the heater as well.

    To make the magnetron smaller I’d start by removing the fins and magnets, the replacing these with smaller neodymiums around the edge and it will then fit inside a heat gun sized casing.

    Use some magnetic viewing film to make sure the field is correct in the centre of the tube where the cavity sits, and it should work.

    Disclaimer.. I haven’t actually built this yet!

    1. Im a Target individual (see stopeg.com), burned all day every day since 2012, prob. before without knowing. Yes, it sucks. I protect myself with inflatable matress with water at home and with a pillow with gel at work. I hope this helps anyone in the same situation.

  14. Yes there is a real risk, so be careful, but if you take proper precautions I could see this being a fun hack for experimenting.

    I would like to see the radiation contained, but in a smaller area so you could directly heat a substance quickly and accurately. — Would make for an awesome piece of equipment in a science lab.

    1. “I would like to see the radiation contained, but in a smaller area so you could directly heat a substance quickly and accurately. — Would make for an awesome piece of equipment in a science lab.”
      you just described a microwave

  15. I think you can wish him minor harm because he not only makes a thing that can definitely mess up other people/animals or technical installations or vehicles (like planes) but he also makes instructions available for others on a site that is not exactly targeted at the highly educated.

    So let the guy that vented alone already.

  16. Take this down for the love of god. Look at the videos you posted they take no safety precautions at all. Not to mention this is very illegal and will do horrible damage to you before you know what is happening.

    The people in the video are complaining about tingling from stray radiation. Not to mention the metallic objects they are irradiating are probably scattering radiation in all directions.

    Is this the behavior that hackaday wants to encourage?!

  17. The real trick is to ditch the control panel and use a charged capacitor bank to trigger the magnetron. Guide it out to a dish and spread the pattern if you wish.

    A number of uses come to mind. No more boom-boom from cars. In fact aim it right, car won’t run.

    For the more devious among us I’m sure you can take this to it’s logical end. Yeah, radio doesn’t like high energy in certain sections like the IF etc.

    Just imagine what you could do with that.

  18. Safety shmafety.

    MY problem is they built a gun without a barrel or a handle in the form of removing the outer parts of a microwave oven, submitted it as a hack…and it was accepted and posted.

    Incomplete, weak…and weak.

  19. OK. coming from the point of view of someone whose job it is repair microwaves and having gone to many schools for microwave repair over the last 15 years, its a miracle they didn’t get killed.

    touching a spark plug on a running engine will give you a solid jolt. it’s about 10,000 volts at about 15-20 miliamps. the transformer microwave puts out about 2,000 volts ac which it bucks up to 4,000 volts dc because of the diode and capacitor, but the power draw of the transformer is 5-8 amps. this won’t just kill you, it turns your brain off and throws you across the room. but if you are determined to do this rather insain experiment, please note the size of the capacitor is determined by the physical size of the inside of the cooking chamber of the microwave, useless tidbit, but if you want to overdrive the magnetron, increase to a capacitor that has a larger microfarad rating. typically they are about 1 uf. i would go to 2 uf or 2.5 but don’t expect the magnetron to last long under these conditions. and for pete’s sake BE CAREFUL

  20. A much better and safer microwave hack, which works even when the microwave is dead, is to disassemble the magnetron for the ring magnets which make the best refrigerator magnets ever.

    Well, second best, the damping magnets from a mechanical analytical balance are actually better, but unless you worked in certain industries during a certain era it’s unlikely you’ll be able to salvage a set of those :-)

  21. That was an interesting observation about beryllium btw gert, wikipedia has some interesting stuff on it and its toxicity, and that’s it’s hard to recognize and they used to determine it by tasting it because it used to be hard to tell if it was beryllium or not. That stuff does indeed sound like tricky business.

  22. This is the lamest HAD post ever. Wow I can light up the phosphor in fluros with a microwave. I disassembled it and now its a hack. The quality of this post is ridiculously bad. Where is the hack here? What did they modify? Lame.

  23. They forgot the tinfoil hats. :)

    But seriously: Don’t do this at home kids. Microwaves are dangerous and not a toy if dismantled. You can get blind playing with unshielded microwaves.

  24. This is in no way a hack. It’s a kid who took apart a microwave, keeping the transformer, voltage doubler, and magnetron.

    The kid in his instructable is proud of hiding this from his parents who would “freak out”. Of course the parents would freak out. Without a horn antenna to focus the power it’s going to be radiating all over the place when it’s turned on. Even with a properly constructed antenna it’s still extremely dangerous because of the kilowatt power levels and the fact that the power is going to be reflecting off of anything it hits. This kid is a danger to himself and others.

    The safety disclaimer in Mike Nathan’s post is wholly insufficient given that the linked project is extremely dangerous and contains no useful information on high-power RF safety.

    I thought that the free energy posts were the worst I’d see on Hackaday. But those were harmless, this is not.

  25. Besides being an Amateur Radio Operator who understands the Dangers of Uncontrolled High Power RF Emissions, I was an independent contractor during the consumer microwave oven boom (Circa 1976-77) preforming factory authorized service on 6 different major brands, it was quite lucrative money wise, but I had to stop after about 18 months because I was getting ill from the low level microwave exposures.
    I rarely use a cell phone to this day unless it’s critical, because the power levels I experienced then are nearly identical to current phone emissions, but I digress. Not only are these guys endangering themselves, anyone down range of that magnetron is endangered at those illegally high power levels. They are setting themselves up for Darwin Awards at those power levels, nice … but please don’t Glorify it on Hack A Day.

  26. as a HAM I must say this is illegal in SO MANY WAYS!

    as a guy That likes HAD i must say
    this is the most effing FU of HAD ever!!!

    next you see a guy with a self made gun shooting at people. Would you publish THAT!! $^%&#$&@%^#^&$#^$#$

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