Blog  /  FM Radio Jammer: How to Make One and Its Application

FM Radio Jammer: How to Make One and Its Application

Blocking radio signals in the early days was pretty easy. And it's because we were using the analog signal for communication. So, all that one needed was a jamming circuit that could produce high-frequency noise signals. But these days, things have evolved, and digital devices have replaced analog devices. Hence, you can only use the FM radio jammer to block signals from getting to the devices.

That said, the jammer works by generating a high-frequency radio signal that confuses the receiver's system from getting the call—regardless of a perfectly working circuit.

Also, the device combines the primary jamming signal with the noise signal. Plus, you can build one with a high-quality PCB—to get the best results.

With that in mind, we'll dig deeper into the topic by explaining more about an FM radio jammer, what you need to make one, detailed steps, etc.

Let's move on!


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What is an FM Radio Jammer?


Like we mentioned earlier, an FM radio jammer is a device that helps to obstruct the transmission or reception of signals.

And it works by producing waves in the form of interference. Interestingly, you can use this device in any location like libraries, offices, restaurants, etc. 


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How Do You Make an FM Radio Jammer?


Before you make an FM radio jammer, it's vital to understand the circuit design. Also, this design is a simple one that would block signals effectively at a meter range of 5 to 10-meter.

So, the first thing is to use alternative sets of L1/L2 alongside 22pF trimmers

With this, you can jam frequencies of 50 MHz to 1 GHz. 

Plus, you can even modify your device to block frequencies as high as 400 MHz; however, it will require more critical parameters. And it may trigger stability issues.


Hence the specification of your device should be:


  1. You should shorten your coils' (L1, L2) diameter or the number of turns. That way, it's easy to make your FM radio jammer tuned to different frequencies.

But, to pull this off easily, it's necessary to do many experiments until you achieve the proper frequency. Plus, you can get different frequencies when you alter the values of the inductor and capacitor.

  1. Adapt your adjacent trimmers with the FM radio jammer kit. And this will help you generate the best possible circuit response.
  1. Opt for a high-quality PCB to ensure that your FM radio jammer gives you the best results.

That said, here are the things you require to build an FM radio jammer:

  • Hard paper
  • A large heatsink
  • Glue
  • Flyback driver
  • Paraffin wax




Step 1


Start by building the jammer’s driver circuit. And you can achieve this by winding the primary coil and feedback similarly. Then, you can protect the transistor when the voltage increases abruptly with a fast diode.

With this, you can use an oversized heatsink. But, it's important to note that we chose a prototype driver that features a tiny heatsink. So, it will make the transistor turn hot fast. Also, since the flyback circuit (primary and secondary) uses screws, you can add other flybacks. Plus, it would help if you had a flyback converter here.


Step 2


In this step, you have to construct the flyback. And you can start by extracting the flyback's primary main coil. Get some of your stiff paper and make a tube. Then, put your coils (primary and secondary) into it and secure them with some glue.

After that, put in the new primary coil, the feedback, and the secondary coil. While at it, it's crucial to ensure that you place the ferrite cores correctly and the synthetic plates are in the right place. With this, you'll notice decreased ultrasound vibrations.

Also, you should note that your magnet wire should be pretty thin (about 0.1mm thick). But your coil should be 1mm thick. Plus, it would help if you didn't have any inner arc within the windings. Further, you'll need the paraffin wax when you're infusing the coil. 

That said, the flyback can produce about 8 to 9mm sparks. But that can increase to 20mm during operation. And it requires a power source of about 20W to work correctly.

In addition, if you decide to add more watts to your flyback, it's necessary to use a handmade thin secondary coil. And it's because if there's a lot of secondary voltage, it can destroy the primary ring. Also, it's best to switch your paraffin wax for epoxy as it melts quickly.


Step 3


Now, it's time for you to install your antenna. First off, you should know that your sparks have a spacing of about 2-3mm. And the antenna you'll use is a 2m wire. So, when the antenna causes a voltage drop, the length of the spark may reduce from about 8mm to 2-3mm.

Since the jammer ranges from 10-15 meters, it's possible to increase the range with a 6-8m antenna. But you may generate more MW noise when you have a long distance. However, you can detect Very High- Frequency noise at a distance of 8-10m. Plus, the jammer could block beyond the longwave band.


Important Points to Note


  • The spark produces ozone.
  • Keep your electronic gadgets safe because the jammer may destroy them from a few meters away.
  • The power supply determines the voltage that a flyback transformer produces. So, it's pretty risky to pump high watts.


How Do You Peak the Resonance?


If you peak the resonance of your DIY FM jammer, it significantly increases its performance. And you can do this with the following considerations:

  1. Get a DC voltmeter with a range of (0 to 10) volts and attach it to the ground line and the point test.
  2. To get a maximum meter reading of 3V, tweak the 22p trimmer on the right side.
  3. Go back to the opposite side (left) of the trimmer (22p). Then, modify it once more to arrive at the right frequency.


Applications of FM Radio Jammers


You can use the FM radio jammers in the following applications:

  • Defense systems like the navy, military, air force, etc.
  • Government offices
  • Highly confidential meetings
  • Broadcasting Stations


Wrapping Up


The FM jammer circuit is an effective device, which blocks radio signals from getting to a receiver's system. No doubt, it's a fun project to execute, but it has some complexities (so you have to be cautious). 

Also, it's important to note that a lot of countries ban the device. Plus, the jammer comes in handy in highly confidential meetings, government offices, etc. 

Do you plan to build this project? Or you're stuck, and you need clarity? Please don't hesitate to hit us up!



Special Offer: Get $100 off your order!

Claim your $100 discount by sending an inquiry today. Act now to save on your next project!
Please email [email protected] for details.