How to Build a Radio/Drone Jammer


Spark gap transmitters are the oldest type of radio transmitter made by man. They were first used around 1888 and remained legal until the 1920s when their use became greatly restricted. World War II delayed their complete ban outside of emergency communications for a few years. Now the only way to use them legally is inside a faraday cage. They operate as jammers for the same reason they were banned, they take up a lot of the radio spectrum.

A spark gap transmitter is fairly simple. Send a high voltage current through an air gap, when the resistance of the air breaks down a spark will cross the gap. When this happens electromagnetic radiation is emitted. You can test this in your house fairly easily. Turn on some speakers so they are powered but nothing is coming out of them. Computer speakers that are on will work as will a stereo set to CD or tape with no CD or tape playing. Flip your room lights on and off in rapid succession, you should hear a clicking from the speakers. The clicking is RF energy that is being picked up from the light switch.

Effective Range

The range of this type of jammer is based on a few properties.

  • Antenna resonance
  • Field strength
  • Modulation
  • Terrain

The antenna of this particular device will be more resonant on one frequency than others. As a result there will be more RF energy on that frequency, and harmonics or multiples of that frequency. The range for this frequency will be further than others. Using multiple antennas will cause the transmissions to be greater on more frequencies.

The field strength, or amount of RF energy given off, is directly related to the difference in voltage between the two states. With the type of transmitter we are making one state will be totally off or 0 volts while the other will be on or the full voltage. It is not required to switch between an off and on state you may switch between a lower and higher voltage as well. The higher the input voltage the stronger the RF, the more range you will have. You have normal free space losses that all radio transmissions have which means that in order to double the effective range you will have to apply 4 times more power.

Another consideration is the modulation that is being utilized. Modulation also includes some of the data that is carried over that mode such as digital data. FM signals for example will lock onto the strongest relative signal from the receivers point of view, a weaker but closer signal will appear stronger than a further but more powerful signal due to free space losses. FM can flip back and forth quickly between two stations that have a nearly equal signal strength at the receivers antenna and make it appear like it is mixing the two stations, the reality is that it is not. SSB will mix the two signals, while you may hear noise in with the desired audio you can still hear the desired audio. Spread spectrum will tolerate the most noise.

Digital systems can be jammed even if the underlying modulation is not by introducing noise the decoding circuitry in the radio may not be able to decipher the bits correctly and reconstruct the message. This can result in heavy packet loss on that system rendering it unusable. Many digital systems are more sensitive to noise than their less sophisticated counterparts. Many digital systems are either FM or spread spectrum. FM is more often used for longer range applications.

The specific type of system that you are trying to jam is important to know as it will tell you how much power you have to have and at what distance. The best way to determine what is suitable is to get a similar system and see how far it will work from the spark gap transmitter at a given power.

Terrain includes buildings, trees and other objects that the radio signals will interact with. If you stash the spark gap transmitter in a metal box the signal will be attenuated compared to that same transmitter being placed in an open field. Elevation can also influence the distance the signal may go.


The construction of this type of spark gap generator is fairly simple. You should be able to get everything for under $50 new, used items may be even less expensive. You will need the following items:

  • high voltage source
  • batteries
  • small bit of wood to mount things on
  • small motor
  • a few nails or screws
  • wire

The high voltage source could be an automotive ignition coil. This takes the battery or alternator output and makes the voltage much higher so that it will jump across the electrodes of a spark plug igniting the fuel. A spark plug is a spark gap, although it is not suitable in its current form as a radio jammer, it could be made into one.

The battery should be suitable to run your high voltage source and the small motor. A motorcycle battery is smaller but will go dead faster than a larger car battery.

The wood should be large enough to let you mount the ignition coil, motor and screws on. This can be any scrap wood or similar non-conductive material that you can find. It should be rigid enough that the components will not just fall apart although it does not have to be that strong. It’s purpose is just to hold everything together. A block of cheese or dried mud would work if that is all you have available.

The small motor can be anything from a vibrator out of an old pager or mobile phone, an electric fan or one you may find at an electronics or hobby store. It just has to have a shaft that allows mounting of a cross member onto.

The first step will be to assemble the motor so that it will function the way you want. When mounting the cross member you should make sure that it is insulated from the rest of the motor either by a plastic shaft or a plastic mounting block. The rod can be a nail although you will want it equidistant from the center.


You can see how the metal rod goes all the way through the plastic insulating block. You may install either one rod all the way through or two rods forming an X. If you install two rods you will have twice the sparks and thus the transmission cycle will be twice as great.


Once the insulating block is mounted on the motor you should affix two other nails or screws on either side so that they almost touch the cross members you installed in the previous step. You do not want them touching but you do want them as close as possible. The closer the better. You should connect the motor to your battery and ensure that it can spin correctly with no problems and that it does not vibrate itself off of the wood.

Now prepare your antenna. This is a length of wire cut to 1/4 wavelength of the desired target frequency. If you do not know the target frequency you can just make some guesses. You can also connect multiple antennas together to cover various frequencies. Remember you will have RF emitted on all frequencies it will just be more powerful on the frequencies that the antenna is resonant for. Mobile phones are about 0.5 inch antennas and older police radios are 2.86 inches. For a good spectrum coverage if you make antennas of 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 inches most of the usable spectrum will be covered.

Connect the antenna(s) that you made to one of the stationary side rods. To the other end you will need to connect a ground. This can be to a metal water pipe in your house or to a rod driven into the ground. If you do not have a ground the radio will still transmit although it will be at a slightly lower power.

Now connect the output of the ignition coil to the stationary rods on either side of the motor. Connect the negative terminal to the ground side and the positive terminal to the side with the antenna(s). The idea here is that when the motor spins current will pass from one rod to the other and out the antenna. The motor will switch the output of the coil on and off in rapid succession.

The last and final step is to connect the battery to the motor and the coil. You may optionally install a switch to turn the device on or off or you may just disconnect the battery.

Remember building this is not illegal (in most places) but using it is. You will be causing harmful interference and probably upsetting people.

51 thoughts on “How to Build a Radio/Drone Jammer

  1. I guess I’m still contemplating the legality of flying drones that may probably be upsetting some people.

    1. I am specifically reading this tutorial to build a frequency jammer on request of a friend who’s family is being harassed by a neighbor quadcopter that has a pattern of hovering where it shouldn’t. unfortunately they cant own the airspace and legally shoot it down. In a pickle for sure.

      1. Google
        DIY HERF GUN or look on You Tube.

        HERF guns are made from old Micro-wave oven diodes. They knock out everything in the sky over your house.

      2. It is illegal to shoot or jam privet aircraft over you property because you do not own the air zone. Plus the FCC, and FAA monitor the air for problems

        1. Only way is to buy fleet of little cheap flybies and accidentally crash them! Easier and cheaper !
          Or train a hawk.

          1. Two improvements come to mind. As for electronic jamming, use a caduceus coil wrapped over PVC pipe with a layer of AL foil between, that will give you a directed scalar beam of high efficiency and distance. (The russians use similar to blind radar, and cannot be shielded.) The PVC pipe could also be a short-range air-cannon loaded with a weighted tangle of fish-line.

        2. It’s called “plausible deniability”. Drones can suffer unfortunate accidents for all sorts of reasons and proving the reason was due to interference or where said interference may have come from is not going to be easy.

          1. I don’t know where you get your info, but you are incorrect. That has been tried throughout the US, some judges have found in favor of the offender, but the drone pilots have failed to challenge the legal standing of the decision.
            The ol’ ruling back to England was that you owned all between heaven and hell, well, that was before the invention of the aircraft. All the rules changed after that, damn those Wright Bros. In some jurisdictions you are said to possess rights up unto 80 feet above your home or property, I imagine that we will see a Ruling by SCOTUS in the next few years.
            Secondly, if the said drone has been issued a FAA number your causing the aircraft to crash is a Federal Offense, punishable with a prison sentence and sizable fine(s).

            My advice, go in doors and play with your toys. Leave the drones alone, you never know when someone learns to enhance one (example: Daesh aka ISIS they drop grenades from their drones).

          2. You can check the type of deed your house has. up until the 1950s many land titles granted the sky above but not anymore.

  2. A simpler and far more effective solution might work like this: A stationary spark gap like this one fed by a high voltage capacitive discharge (warning!!!! VERY dangerous,deadly in fact if you touch any part of the circuit while active and even for several hours later),in turn fed to one end of an old T.V. antenna ,the other end attached to a good earth ground, ought to drop those monstrosities like mallards during duck season.Placing powerful neo magnets across the gap in a North-South configuration will interrupt the spark very abruptly and create spikes an order of magnitude greater than without them(an old Tesla trick). The frequency can be adjusted by the distance between the gap.Of course I must insist you don`t try this for any reason because of the obvious danger and illegality of it all,plus the fact that those drones are only up their to protect you from right wing Jee-zus humping gun nuts. Obama loves you after all 😉

    I suspect something like the above is how the Iranians are doing it.

      1. CAP sizes and resistor sizes along with wattages of each. Have you taken a spectrum analyzer to determine frequencies depended upon gap settings. This is essential to know former ECCM countermeasures radar tech. USN

    1. I have micro Drones W/cameras that seem to be window shopping my girls…
      I know I don’t own the air space however these fly around land take off the landing should be illegal??? after all the land is mine

      1. They make special shotgun shells for taking down these drones. You can get them at
        Now make sure your wear your coronavirus mask, safety glasses, and gloves and enforce your right to privacy. This is a criminal act being perpetrated on you. Treat it as such.

  3. I know nothing about radio frequency or electronics and was just wondering:
    The jammer built in this article is very very small, tiny in fact. This is enough to jam a drone? What is the range, (distance)? Would a larger one using larger components work better or reach out farther?

  4. If you are using an ignition coil you would need to be switching the low voltage side of the coil to produce high voltage on the output side. As far as I know a constant current will not work.

    1. your good to go if the coil is off a solid state ignition system, which he failed to mention in the article. your thinking of cdi ignition coils, which is controlled by a low voltage signal input from the ecu

      1. Slap a pulse generator on it and then you can vary out put frequencies to cover a wide variety of drones. Most RC planes can be jammed just by using a fm cb radio…………..but ya got to be close 4 watts max output.

        Everything depends on what is controlling the drone if its satellite your gonna have to have a microwave frequency generator to affect it.

  5. neon sign transformers are great. also some old antique devices totally rock. when a kid i accidentally jammed everything for MILES with an old daithermy machine i connected to a long antenna.

  6. the diathermy machine i used was stronger than the one marconi transmitted across the atlantic. it had 6 adjustable spark gaps and could vaporize #12 copper wire. still have the scar and remeber the pain when it burnt a hole in my thumb. came in a beautiful oak cabinet, and then main switch was 1/4″ copper bars. figure it was 2 kw min.

  7. old model t spark coils also work great, once you add a spark gap- have one- my emergency transmitter

  8. I must say something here that I don’t see hardly anywhere. Being a non member and just following a link in please understand I don’t know anything about the site or group. But this assumes that you have electricity! This ain’t necessarily so. I see a lot of apparent thinking that the power and internet will be on and working without any restrictions. I believe that there is at least there is a 95% chance that this thinking is wrong. Discounting the possibility that the switch will be thrown it takes so little damage to put a large area out of operation. These same restrictions apply to renewable power sources as well. A solar array or a windmill will be easy to see from a drone. Think about these things and what can be done to protect them and you from the unusual. Also pick everything apart to the smallest detail to find it’s weakness because Murphy is always walking by your side.
    R D

    1. A hand powered alternator connected to a bycyle works just great with a regulator system to recharge batteries…………

  9. Now ve can make them to down all Amerikan drones in Afghanistan and anywhere else – wupeee !!

  10. If anyone is interested in the theory behind this, a good video on radio in general and spark gap transmitters in particular is available at:
    It is an old episode of The Secret Life of Machines from the BBC. It shows the original spark gap transmitter and modern homemade equivalents, including theory.

  11. Military drones use redundancy control systems. Although it is common for line of sight radio transmission, they are backed up and usually, primarily controlled by a direct satellite link. This can also be jammed using a standard satellite dish from your rooftop. You must jam both and override its GPS “return home” autopilot when it loses connection. I would suggest that this is better for jamming communication in an emergency more so than drones. A quick Google search well give you details on jamming the sat link.

  12. Im having an issue with wiring. So I connect the output of the ignition coil (the output is the center whire which usually goes to the destributor?) to bothe rods? So I bring two wires from the output; one hooks to the antenna and one hooks to the ground? Also, what do I wire the battery to? Thanks

  13. The motor can be done away with completely by cross wiring a dual throw four pole relay to create an interupter. Wire the power through the normally closed contacts, when it’s energized, the electromagnet opens the contacts, breaking the circuit which closes the contacts energizing the circuit again.

  14. Great little project! I will dust off my old plans for a localized EMP generator to add to this useful group. Thanks for this information.

  15. your link to the Faraday cage is no longer relevant. No content on the otherside.

    Thanks for sharing the jammer info!

  16. It IS possible to build a Drone DOS (Denial Of Service) system that takes over frequencies from 900MHz-5.8GHz using microwave antenna/radio gear an by using radio frequency amplifiers then adjusting the antennas and offsetting fresnel.
    They have a government one that sells for a million. Mine costs about $500 and works for 5 miles. I used it in a rural area, checked for other freqs with my frequency spectrum analyzer to make sure I didn’t “step” on anyone or get in trouble. I would love to be able to patent it and have a legal way to build and test it, but like many other inventions of mine, it will go in my bunker on the shelves to be covered with dust.
    It made my drone crash within 1-3 min at a max of 5 miles away every time. The drone was controlled 5 miles away, not beside me.

    1. Any chance id b willing to help a guy out and make another I’v tried without much success but I’d b willing to pay cash 4 a nice working setup iv had all I can take from idiots and law enforcement that use them to invade my privacy.. call or text me anytime if interested drone guy thanks, 6two0seven6twotwoeight6seven

  17. The instructions of where to connect the antenna(s), ground, positive and negative are hard to follow. I do not understand where to connect. They should be more detailed

    Also nowhere in the article is it mentioned what the probable distance of jamming would be. That’s like the most important thing

Join the Conversation

Your email address will not be published. Required fields are marked *