Cell Phone Jammer Circuit

Our addiction to technological development has made it so that it is almost impossible to imagine a day without those amazing inventions. Cell phones popular as mobile phones are the ones we cannot separate from the essential list. By now, they have become an inseparable part of our lives. Talking about a country like Nepal which has a low population (approx. 5 million), mainly two categories of cell phone carriers are available namely; NTC and Ncell. They use GSM 900 or 1800 systems. The systems have been upgraded to 3G recently. Like there is a bad side to every aspect, excessive use and ringing of mobile phones becomes annoying or disrupting at certain events. This might create serious issues in some places like conference rooms, law courts, libraries, lecture rooms and mosques.

A device comes in handy at such situations where one needs to stop this disrupting ringing and that device is named as a cell phone jammer or ‘GSM jammer’ in technical terms, whose sole purpose is to inhibit the use of mobiles, i.e., make them obsolete. Basically it is an electronic countermeasure device.  There is a simple technology behind the entire concept of cell phone jamming.

The jamming device broadcasts an RF signal in the frequency range reserved for cell phones that interferes with the cell phone signal, which results in a “no network available” display on the cell phone screen. Because of which, all phones within the effective radius of the jammer are silenced. Keeping aside the convenience of this device, it has been declared illegal in most countries. According to the Federal Communications Commission (FCC) in the USA; “The manufacture, importation, sale, or offer for sale, of devices designed to block or jam wireless transmissions is prohibited”. However recently, there has been an increasing demand for portable cell phone jammers. We should mention that this project, presented in this report, is solely done for educational purposes. There is no intention to manufacture or sell such devices in Nepal, or elsewhere. In this project, a device that will jam both GSM 900 and GSM 1800 services will be designed, built, and tested.

cell phone jammer circuit
Resistors (all ¼-watt, ± 5% Carbon)
R1 = 250 Ω
R2 = 750 Ω
R3, R4, R6= 2 KΩ
R5 = 100 KΩ
R7 = 10 Ω
R8, R9 = 1 KΩ
R10 = 2 KΩ
C1, C3 – C7, C9 = 0.1 µF
C2, C15, C16 = 1nF
C8, C10 = 10 µF
C11, C13 = 4.7 µF
C12, C14 = 0.01 µ
IC1 = NE555
IC2 = LM741
IC3 = LM386
IC4, IC5 = PF08109B
T1 = 2N3904
ZD1 = 6.8V Zener Diode
D1, D2 = 1N4148
Antenna 1 = GSM antenna (Frequency = 850MHz-1GHz, Input Impedance = 50Ω, VSWR<2)
Antenna 2 = DCS antenna (Frequency = 1700MHz-1900MHz, Input Impedance = 50Ω, VSWR<2)