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May 31, 2022

How does a signal jammer work?

How do signal jammers work? This is a question from many people.

As we enter the second decade of the 21st century, digital technology seems to have completely taken over our lives, and it feels like we are simply reduced to a series of signals. Signals have even taken over our language. With the rapid development of the mobile Internet, life is all wrapped up in the world of signals all the time. 5G signals are already popular in most cities.

How does a signal jammer work?

On a more serious level, with so much communication around us, people and organizations are taking a good long look at different types of signal jammers to quell the noise and limit how much of it is going around. While there is a wide variety of signal types, the way signal jammers work is actually pretty straightforward. Once you know the frequency of your target signal, simply overpower that signal by emitting a stronger signal of your own. If you want to target not just a device, but the signal traffic in general, point your jammer at the base station/relay antenna (for example, mobile phone jammers used in public places to preserve silence). The further away it is, the more power you need to drown it out. If the signal jumps frequencies, cast a wider blanket of signal disruption by covering a range of frequencies. Sometimes, as with drone jammers, the jamming signal needs to be narrowly focused in a specific direction.

What are the young folks jamming to these days?

Younger generations, having grown up with so much ‘signal pollution’, they are willing to welcome various jamming technologies to help clean that up. At home, they are adopting mobile phone jammers, in order to take more control of their lives. These devices can define quiet, ‘no-phone zones’ for a better quality of life. In many families, there are 1.5 devices per person and it is hard to have a meaningful conversation with all these screens in the way. Young parents are realizing that the intimacy of a family dinner is in danger of extinction. To avoid conflicts, they are turning to mobile phone jammers to both to enforce ‘dinnertime’ and to help rediscover ‘cellphone discipline’.

In the workplace, organizations have come to understand that protecting sensitive proprietary and personal data may require them to use Wifi jammers around the office, that will provide security by preventing data from leaking out or from being stolen. And the exponential growth of drones and their sometimes nefarious purposes has convinced security-minded professionals to deploy drone jammers as a standard operating procedure to protect people and places.

How can I make a mobile jammer?

A Mobile Jammer Circuit or a Cell Phone Jammer Circuit is an instrument or device that can prevent the reception of signals by Mobile Phones. Basically, a Mobile Jammer Circuit is an RF Transmitter, which broadcasts Radio Signals in the same (or similar) frequency range of the GSM Communication.

WARNING: Blocking or Jamming Radio Signals is illegal in most countries. Check your local laws before using such devices.

In this project, I have designed two Mobile Jammer Circuits, where the first one is using a 555 Timer IC and the other one is built using active and passive components.

Circuit 1: Mobile Jammer Circuit using 555

Components Required

  • 555 Timer IC
  • Resistors – 220Ω x 2, 5.6KΩ, 6.8KΩ, 10KΩ, 82KΩ
  • Capacitors – 2pF, 3.3pF, 4.7pF, 47pF, 0.1µF, 4.7µF, 47µF
  • 30pF Trimmer Capacitor
  • LED
  • Coils 3 Turn 24 AWG, 4 Turn 24 AWG
  • Antenna 15 Turn 24 AWG
  • BF495 Transistor
  • ON / OFF Switch
  • 9V Battery


After building this circuit on a perf board and supplying power to it, I have placed a mobile phone near the circuit (I am yet to turn on the switch). Before turning on the power, my mobile phone was able to capture majority of the signals as it is displaying full bars.

Once I turned on the circuit, the signal bars on the phone started to reduce and finally it stopped at a single bar.

So, in conclusion, I can say that this circuit blocks the signals but cannot completely jam them.


Circuit 2: Simple Mobile Jammer Circuit Diagram


Cell Phone Jammer Circuit Explanation

If you understand the above circuit, this circuit analysis is simple and easy. For any jammer circuit, remember that there are three main important circuits. When they are combined together, the output of that circuit will work as a jammer. The three circuits are

  • RF amplifier.
  • Voltage controlled oscillator.
  • Tuning circuit.

So the transistor Q1, capacitors C4 & C5 and resistor R1 constitute the RF amplifier circuit. This will amplify the signal generated by the tuned circuit. The amplification signal is given to the antenna through C6 capacitor. Capacitor C6 will remove the DC and allow only the AC signal which is transmitted in the air.

When the transistor Q1 is turned ON, the tuned circuit at the collector will get turned ON. The tuned circuit consists of capacitor C1 and inductor L1. This tuned circuit will act as an oscillator with zero resistance.

This oscillator or tuned circuit will produce the very high frequency with minimum damping. The both inductor and capacitor of tuned circuit will oscillate at its resonating frequency.

The tuned circuit operation is very simple and easy to understand. When the circuit gets ON, the voltage is stored by the capacitor according to its capacity. The main function of capacitor is to store electric energy. Once the capacitor is completely charged, it will allow the charge to flow through inductor. We know that inductor is used to store magnetic energy. When the current is flowing across the inductor, it will store the magnetic energy by this voltage across the capacitor and will get decreased, at some point complete magnetic energy is stored by inductor and the charge or voltage across the capacitor will be zero.

The magnetic charge through the inductor will decreased and the current will charge the capacitor in opposite or reverse polarity manner. Again after some period of time, capacitor will get completely charged and magnetic energy across the inductor will be completely zero. Again the capacitor will give charge to the inductor and becomes zero. After some time, inductor will give charge to capacitor and become zero and they will oscillate and generate the frequency.

This circle run upto the internal resistance is generated and oscillations will get stop. RF amplifier feed is given through the capacitor C5 to the collector terminal before C6 for gain or like a boost signal to the tuned circuit signal. The capacitors C2 and C3 are used for generating the noise for the frequency generated by the tuned circuit. Capacitors C2 and C3 will generate the electronic pulses in some random fashion (technically called noise).

The feedback back or boost given by the RF amplifier, frequency generated by the tuned circuit, the noise signal generated by the capacitors C2 and C3 will be combined, amplified and transmitted to the air.

Cell phone works at the frequency of 450 MHz frequency. To block this 450MHz frequency, we also need to generate 450Mhz frequency with some noise which will act as simple blocking signal, because cell phone receiver will not be able to understand to which signal it has been received. By this, we can able to block the cell phone signal from reaching the cell phones.

So here in the above circuit, we generated the 450 MHz frequency to block the actual cell phone signal. That’s what the above circuit will act as a jammer for blocking the actual signal.





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