A device that cuts off the signal between a mobile phone and a tower is known as a mobile phone jammer.
It achieves this by disrupting with communication by using the same radio frequencies as a cell phone.
Several networks including 3G, 4G and even older ones can have calls and texts blocked by this circuit.
Three essential components are often included in a mobile phone jammer:
- To increase the signals power one should use an amplifier.
- A special circuit that generates the right radio waves.
- This device than modifies radio waves to connect with telephone signals.
When these components come together the mobile phone signal is jammed.
Circuit working:
Parts List:
| Component | Quantity |
|---|---|
| Resistors (All resistors are 1/4 watt) | |
| 39k | 1 |
| 100Ω | 1 |
| Capacitors | |
| Ceramic 0.049pF | 1 |
| Ceramic 102pF | 1 |
| Ceramic 1uF | 1 |
| Ceramic 2.2pF | 1 |
| Ceramic 103pF | 1 |
| Ceramic 4.7pF | 2 |
| Semiconductors | |
| Transistor 2N2219 | 1 |
| Inductor 1uH | 1 |
| Antenna | 1 |
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 such as 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 stop.
Prior to C6 integrating and boosting the frequency produced by the tuned circuit with noise signals produced by capacitors C2 and C3 the RF amplifier supply is sent to the collector terminal through capacitor C5.
This results in 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 the area operate at 450 MHz needs to generate a signal at 450 MHz with some noise to serve as the blocking signal causing the cell phone receiver unable to identify the correct signal.
It is important to note that this circuit has a limited range of approximately 100 meters.
Also 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 simple LC circuit is found using the below formula where:
F = 1/(2 x π x √(L1 x C1))
where,
- The circuits maximum oscillation or resonance is indicated by the frequency F which is shown in Hz hertz.
- The value of the mathematical constant π (pi) is about 3.14159.
- Henrys H inductors prevent changes in current and store energy in a magnetic field the circuits inductance is represented by L1.
- Capacitors store electrical energy in an electrostatic field as C1 indicates in farads F.
Knowing the Formula:
Impedance and Resonance:
The formula connects the capacitance C and inductance L to the resonant frequency.
At a specific frequency the inductor and capacitor in an LC circuit oppose reactive effects or imaginary resistance to current flow.
When the inductive reactance XL of the inductor balances out the capacitive reactance XC of the capacitor resonance takes place at this frequency.
Term for Square Root:
The square root term √(L1 x C1) represents the combined reactance of the inductor and capacitor at a specific frequency.
At resonance this total reactance is zero.
Factor 2π:
The reactance phrase is changed into a term that indicates frequency by the factor 2π.
In AC circuits frequency and reactance are connected by means of this mathematical conversion factor.
In simple words the formula gives the frequency at which the LC circuit resonantly occurs as a result of the inductor and capacitors reactive effects balancing out.
Conclusion:
Due to their ability to disturb essential communication and emergency calls mobile phone jammers are illegal in several nations.
They can also interfere with other nearby peoples lawful mobile phone use.
Therefore it is strongly advised that no one should create or use such devices.