Simple Mobile Phone Signal Jammer Circuit

A cell phone jammer is a device that blocks the signal between your phone and the cell phone tower.

It does this by using the same radio waves as your phone, which messes up the communication.

This can block calls and texts on different networks like 3G, 4G and even older ones.

A cell phone jammer typically has three important parts:

• An amplifier to make the signal stronger.
• A special circuit to create the right radio waves.
• A tuner to adjust the radio waves to match the phone signal.

These parts work together to jam the cell phone signal.

Circuit working:

Parts List:

The RF amplifier circuit includes transistor Q1, capacitors C4, C5 and resistor R1.

This circuit amplifies the signal generated by the tuned circuit, and the amplified signal is transmitted to the antenna through capacitor C6 blocking DC and allowing only the AC component to pass.

When transistor Q1 is activated, the tuned circuit at the collector is also activated.

This tuned circuit, comprising capacitor C1 and inductor L1 acts as an oscillator with minimal resistance producing a very high frequency.

The process involves the charging and discharging of the capacitor resulting in oscillations until internal resistance is generated, causing the oscillations to cease.

The RF amplifier feed, given through capacitor C5 to the collector terminal before C6 combines and amplifies the frequency generated by the tuned circuit with noise signals generated by capacitors C2 and C3 creating a combined amplified, and transmitted signal.

Mobile phones operate at various frequency bands globally.

To calculate the required values for the jammer circuit the formula is mentioned below.

Depending on the frequencies to be blocked, the values of the inductor L1 and capacitor C1 can be adjusted accordingly.

For example, if mobile phones in your area operate at 450MHz you need to generate a signal at 450 MHz with some noise to serve as the blocking signal rendering the cell phone receiver unable to distinguish the correct signal.

It is important to note that this circuit has a limited range of approximately 100 meters.

Additionally, the usage of such circuits is illegal in most countries, and this information is provided for educational purposes only.

Formula:

The resonant frequency (F) of a basic LC circuit may be found using this below formula, where:

F = 1/(2 x π x √(L1 x C1))

where,

• F: shows the frequency in Hz hertz.
• This frequency represents the greatest oscillation or resonance that the circuit shows.
• π (pi): The value of this mathematical constant is around 3.14159.
• L1: represents the circuits inductance in henrys H.
• Inductors store energy in a magnetic field and resist current fluctuations.
• C1: shows the circuits capacitance in farads F.
• Electrical energy is stored in an electrostatic field by capacitors.

Knowing the Formula:

Resonance and Impedance: The formula links the resonant frequency to the inductance L and capacitance C.

Reactive effects, or imaginary resistance to current flow, are opposed by the inductor and capacitor in an LC circuit at a certain frequency.

Resonance occurs at this frequency when the capacitive reactance XC of the capacitor is cancelled out by the inductive reactance XL of the inductor.

Square Root Term: At a given frequency, the combined reactance of the inductor and capacitor is represented by the square root term, √(L1 x C1).

This overall reactance equals 0 at resonance.

Factor 2π: The reactance term is transformed into a word that represents frequency by the factor 2π.

In AC circuits, this mathematical conversion factor is used to relate reactance and frequency.

All things considered, the formula basically determines the frequency at which the reactive effects of the capacitor and inductor cancel each other out and cause the LC circuit to resonant.

Conclusion:

It is important to note that the use of mobile phone jammers is illegal in many countries due to their potential to interfere with emergency calls and essential communications.

They can also disrupt legitimate use of mobile phones by others in the vicinity.

As such, it is strongly advised not to engage in the creation or use of such devices.

References:

Simple Mobile Phone Jammer Circuit Diagram

Design and Testing of a Mobile-Phone-Jammer