How Cell Phone Jammer Works?

How Cell Phone Jammer Works?
By Sarvjit Rangra / September 18, 2017

At present, most people own a cell phone. It is a convenient way of staying in touch with friends and loved ones. But because of the increased use of cell phones, there are places that suffer because people don’t know when to stop using their phones. That’s why the cell phone jammer was invented. It allows the user to disrupt the signal going to and from the phone.

The principle behind interrupting the cell phone is similar to jamming other types of radio communication. In order to use a cell phone, a signal is sent from the phone to the cell tower. There are several cell towers in a city. As a cell phone user moves in an area, the signal is handled by one tower to another.

A signal jammer transmits on the same radio frequency as the cell phone. It interrupts the communication between the cell phone and the base station found in the tower. The jamming is also known as a denial of service attack because it denies the service of the radio signal to users within the coverage area of the jamming device.

The jammer overpowers the cell phone by transmitting on the same radio frequency. It has enough power to cancel out the cellular signal. Cell phones are made to add power if they experience low-level interference, so the jamming device has to much the power increase made by the phone.

A cellular phone is a full-duplex device that utilises two frequencies at the same time. One is for talking while the other is for listening. The signals are handled at the same time. There are signal jammers that can only block one of the frequencies at a time, which results to the blocking of both because the phone thinks that there is no service in the area because it can only get one of the frequencies.

There are different types of cell phone jammers on the market today. Some devices can only block a single frequency while there are complex ones that can block several types of networks at the same time. The latter models can automatically switch from different networks to find an open signal. Higher end devices can block all frequencies at the same time while there are others that can be tuned to a specific frequency.

In order to jam a cell phone, you need a device that will broadcast on the right frequencies. Although cell systems process signals in different manners, networks utilise radio signals that can be blocked. GSM networks use 900 MHz and 1800 MHz bands in Asia and Europe, and in 1900 MHz in the US. Cell phone jammers can broadcast on various frequencies and can be used on CDMA, GSM, TDMA, AMPS, DCS, iDEN, Nextel, and PCS networks. That means analogue and digital mobile phones can be jammed with the right tool.

The coverage of the cell phone jammer depends on the local environment and the power. Walls of the building and hills can affect the effectiveness of the signal jammer. Low powered devices can block calls within a 9 metre radius. High powered devices can jam the signal up to a 1.6 km radius.

Parts of a Cell Phone Jammer

When you disassemble a cell phone jammer, you’ll discover that it is a very simple device. On the outside, it has a power switch and a light to indicate that it is on. Complex jammers have switches that allow users to change the frequencies to be jammed. The parts of a jammer include:


A cell phone jammer has an antenna to allow it to send signal out. There are models that have the antenna within the casing. On high powered devices, antennas are on the outside to have a wider range and can be tuned for specific frequencies.

Jammer Circuit

The main elements of a jammer include a voltage-controlled oscillator, noise generator, RF amplification, tuning circuit, and power supply. The oscillator generates the radio signal that interrupts the cell phone signal. The tuning circuit controls the frequency in which the jammer broadcasts the signal by transmitting a voltage towards the oscillator. The noise generator creates random electronic output within a frequency range to disrupt the signal of the cell network. The RF amplification allows the jammer to boost the signal output in order to jam the signal. Small jammers are powered by batteries, but stronger devices are required to be plugged into a standard outlet. There are some devices that can be wired into the car’s electrical system.

Uses of Cell Phone Jammer

Cell phone jammers were initially designed for military and law enforcement use. They were developed to disrupt communications by terrorists and criminals. Terrorists use cell phones to trigger bombs. Law enforcement agencies across the globe use signal jammers to prevent terror attacks. There are some companies use cell phone jammers to block communications within sensitive areas to prevent corporate espionage.

In the United Kingdom, it is illegal to block cell phone services. Some see it as property theft because the cellular service provider has purchased the rights to the specific radio spectrum. Jamming the signal is likened to stealing a property that was purchased by the company.

In most countries, private citizens are not allowed to own a cell phone jammer but they allow businesses and other organisations to install one in their premises where cell phone usage has been seen as public nuisance. Take for instance France, where it is legal for jammers to be used in concert halls, theatres and other venues with performances. It was also reported that universities in Italy are using the device to prevent cheating. People welcome the use of such device in weddings, movies, and classrooms because it prevents annoyances caused by cell phone users.

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