# DIY Mobile Phone Signal Jammer| Simple Homemade|

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## Introduction: DIY Mobile Phone Signal Jammer| Simple Homemade|

Hi Friends I'm Aravind Chowdary. And today we are going to know about How a mobile signal jammer works and how easy it is to build it by ourselves at our home. Let's get Started.

Firstly a mobile phone jammer or blocker is a device which deliberately transmits signals on the same radio frequencies as mobile phones, disrupting the communication between the phone and the cell-phone base station, effectively disabling mobile phones within the range of the jammer, preventing them from receiving signals and from transmitting them.

They disrupt the operations of legitimate mobile phone services, the use of such blocking devices is illegal in many jurisdictions, especially without a licence. When operational, such devices also block access to emergency services.

Let's move on to design of the project.

## Step 1: Design the Circuit

To design our circuit we must have some basic knowledge how a jammer works.

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. 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.

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

Depending on the frequencies you need to block, the values of inductor (L1) and capacitor (C1) can be altered. For example, if mobile phones at 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.

## Step 2: Description:

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

RF amplifier

Voltage controlled oscillator

Tuning circuit

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

Now, what is an voltage controlled oscillator.(VCO)

In simple terms, a VCO is an electronic oscillator whose oscillationfrequency is controlled by a voltage input. The applied input voltage determines the instantaneous oscillation frequency. Consequently, a VCO can be used for frequency modulation (FM) or phase modulation (PM) by applying a modulatingsignal to the control input. A VCO is also an integral part of a phase-locked loop.

## Step 3: Working of the Jammer

RF amplifier circuit comprises of the 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, 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 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.

## Step 4: Gather All the Components Needed

Resistor R2 - Base Biasing

CapacitorC1 - Frequency Generation

CapacitorC2 - Feedback

CapacitorC3 - Feedback

CapacitorC4 - Noise Reduction

CapacitorC5 - Coupling

CapacitorC6 - Coupling

CapacitorC7 - Decoupling

TransistorQ1 - Amplification

InductorL1 - Frequency Generation

## Step 5: First Make a Pcb Prototype

If all the things works well then move on to the pcb prototype.

## Step 6: Now Follow the Circuit in the Above Step to Make a Pcb Prototype.

Now carefully follow the circuit diagram and complete soldering all the parts to the pcb board.

It took me 45mins to solder all the parts and make a working model.

This circuit can block signals only within a 100 meter radius.

Usage of this type of circuits 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 resistor and capacitors values in the circuit. Use the formula

F= 1/ (2*pi*sqrt (L*C)).
Power supply for the circuit should not exceed 3 Volts.

## Step 7: Worked

It really worked for me in the second time after using the formula and changing the capacities of ceramic caps

It turned my signal points into zero. Thanks for reading my instructable. Happy jamming!!

## Step 8: Notice

Note that these type of gadgets are illegal.

Because they disrupt the operations of legitimate mobile phone services, the use of such blocking devices is illegal in many jurisdictions, especially without a licence. When operational, such devices also block access to emergency services.

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