Wednesday, April 24, 2024

How to Build Cell Phone Signal Jammer

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A cell phone Signal jammer is an electronic device that blocks the transmission of signals between a cell phone and a base station.

By using the same frequency as a mobile handset, the signal jammer creates strong interference in communication between the caller and receiver.

It is effective in blocking the transmission of signals from networks including UMTS, 3G, CDMA, GSM, and PHS.

DIY Cell Phone Signal Jammer – Components Required

Resistor R1Emitter Loading
Resistor R2Base Biasing
Capacitor C1Frequency Generation
Capacitor C2Feedback
Capacitor C3Feedback
Capacitor C4Noise Reduction
Capacitor C5Coupling
Capacitor C6Coupling
Capacitor C7Decoupling
Transistor Q1Amplification
Inductor L1Frequency Generation

Cell Phone Signal Jammer Circuit

Cell phone Signal jammer circuit
Mobile Signal Jammer Circuit Diagram

For any jammer circuit, it’s essential to have three important subcircuits.

These 3 circuits, when combined together form an efficient cell phone jammer circuit.

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Cell Phone Signal Jammer Working 

  • RF amplifier circuit comprises transistor Q1, capacitors C4, C5, and resistor R1. This RF circuit amplifies the signal generated by the tuned circuit. The amplified signal is given to the antenna through capacitor C6. It blocks DC and allows only the AC component of the signal to be transmitted.
  • When transistor Q1 is turned ON, the tuned circuit at the collector turns ON. The tuned circuit consists of capacitor C1 and inductor L1. This acts as an oscillator with zero resistance. It produces very high frequency with minimum damping.
  • When the circuit is ON, voltage is stored in the capacitor. Once the capacitor is completely charged, it allows charge to flow through the inductor. When current flows through the inductor, it stores magnetic energy corresponding to the voltage across the capacitor. At a certain point, the inductor reaches its maximum and the charge or voltage across the capacitor turns to zero.
  • Now the magnetic charge through the inductor decreases and the current charges the capacitor in opposite or reverse polarity. The process repeats and after a while, the inductor charges the capacitor and becomes zero.
  • This process runs till internal resistance is generated and the oscillations stop. RF amplifier feed is given through capacitor C5 to the collector terminal before C6. The capacitors C2 and C3 generate pulses in a random fashion (noise) at the frequency generated by the tuned circuit.
  • The RF amplifier boosts the frequency generated by the tuned circuit. The frequency generated by the tuned circuit and the noise signal generated by the capacitors C2 and C3 is combined, amplified, and transmitted.

Mobile Frequency Jamming Calculation

Mobile phones operate at different frequency bands in different countries. For Canada, the 1900 MHz band is the primary band, particularly for urban areas. 850 MHz is used as a backup in rural areas. The USA uses 850 and 1900 MHz bands, depending on the area.

Europeans tend to use the GSM 900 and 1800 bands as standard. Middle East, Africa, Asia, and Oceania also use these frequency bands. In Russia and some other countries, local carriers have licenses for 450 MHz frequency to provide CDMA coverage.

The use of different frequencies makes it difficult to have a jammer for all frequencies. However, the below-mentioned formula can be used to calculate the required values.

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F = 1/(2*pi*sqrt(L1*C1))

Depending on the frequencies you need to block, the values of the inductor (L1) and capacitor (C1) can be altered.

For example, if mobile phones in your area work at 450 MHz, you need to generate 450 MHz with some noise to act as the blocking signal.

Now the cell phone receiver will not be able to understand, which signal to receive. We have successfully blocked cell phone signals.

Here, 450MHz is the tuning frequency. Cell phone jammers for other frequency ranges are designed similarly. However, the signal range is very weak. Thus, this circuit works only for a range of 100 m.


  • This circuit can block signals only within a 100-meter radius.
  • Usage of this type of circuit is banned and illegal in most countries.
  • This circuit is also used in TV transmission and remote-controlled toys.
  • If the circuit is not working properly, try increasing the resistor and capacitors values in the circuit. Use the formula given above.
  • The power supply for the circuit should not exceed 3 Volts.

We have more such interesting DIY Electronics Projects for you.

Note: The cell phone jammer is an untested prototype circuit and is banned in several countries. Keeping in with those regulations, we might not be able to help you out with the exact values.

This article was first published on 17 October 2017 and recently updated on August 2023.


  1. If already have a jammer, how to improve its working range?
    I bought a jammer on , but I found that the interference range is not enough. Can I improve the interference range by modifying the circuit?

  2. I am amazed at the people commenting on here. If you have read the 20+ times that the team has said this is simply a concept a.k.a. =
    a prototype. And if you do not know what a prototype is and yet have the ability to post the question, you then also have the ability to search the internet for the answer. This is not for entry level or rookie skill level. If there is anything unclear to you here then this is simply above you skill level. You need senior to expert level experience and knowledge of Electrical, RF, PCB and/or telecom. Engineering

    • Exactly, and what makes me wonder is why they are all in such dire need of such a device?
      They should not be messing around with RF transmitter circuits in the first place. This is a fine example of people, “knowing just enough to be dangerous!”.

      They may as well take an old microwave oven apart, grab a hold of the magnetron, and aim it at their victim and fire it up!
      Opps, maybe I shouldn’t give any ideas like that! Lol ?

  3. What about CDMA, W-CDMA and LTE,etc.. will it work properly because these technologies uses spread spectrum rather than a single frequency.
    I want to create one for 2300 mhz. So to increase the frequency only L1 and C1 has to be changed or any other components as well like R1,C7,etc ?
    Looking forward for your answer. Please Do help.

  4. Yaaah u are really right of the circuit diagram u just display but it is too noisy asas compared to how u said the c4 reduceses noise but rather the sound more inflicted within the circuit. I did I project which will be able to provide a mosque with LEDs display .after some time I got to know dat , mobile phones ring and bells in the mosque where by we are praying .
    So I decided to make a stop to it by making it work so jamm the signal range within the mosques not any other place , so I made several research about how to jamm mobile phones , so I made research and it brought me through success and I was able to make it, but unwantedly it affects the microphone player system within the mosque with made the speaking more difficult and the sound was not spicing out well but rather created a radio active signal noise piiiiiiiiiiiin

  5. Hello there. I want to make a mobile signal jammer like this for a autistic child. He spends his time most of on useing mobile phone and he is start to act rude and attacker. He playing games and watching videos online. Actually that videos have violence and more. So the kid becoming to dangerous person. All i want make a simple and tiny circuit for block phone cell in 2 squaremeters. Can you please help me ? i tried this circuit but this doesn’t work. if you help me, we will be greatful to you. thanks alot. with all respect.

  6. You say the target freq. for the circuit is 450 Mhz but for the given inductor and capacitor C1 it would generate a ~277 Mhz signal, am I missing something? Or how can i amplify it to 450mhz thanks


  7. The jamming system transmits adequate power radio signals to cut-off communications between cell phones and cellular base-stations.Mobile Jammer is available in different models depending upon the output power.
    Upon activating Cell phone jammer, all idle phones will indicate “NO SERVICE”. When the cell phone jammer is turned off, all cell phones will automatically re-establish communications and provide full service.


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