How does Cell Phone Jammer Work?

June 29, 2022

How does Cell Phone Jammer Work?

Mobile phones have become the most valuable portable items in the world. Mobile phones are everywhere in the world, and 5G is also updating the network simultaneously. Better service is on the way.
Unfortunately, restaurants, movie theaters, concerts, shopping malls, and churches are all affected by the proliferation of mobile phones because not all mobile phone users know when to stop talking. When the talker shares intimate details with his friends and others in the area, who hasn’t talked about an incredibly personal situation through one side of the conversation?

While most of us just complain and move on, some will take extreme measures in retaliation. Cell phones are handheld two-way radios. As with any radio, the signal may be interrupted or interfered with.

In this article, we will focus on explaining how it is used.

Interfering with a cell phone is the same as interfering with any other type of radio communication. Cell phones work by communicating with their serving network through cell towers or base stations. Cell towers divide cities into small areas or cells. When a cell phone user drives down the street, the signal is passed from tower to tower.
The jamming device transmits on the same radio frequency as the cell phone, disrupting the communication between the cell phone and the cell phone base station in the tower.
This is called a denial of service attack. Jammers deny radio spectrum service to cell phone users within range of the jamming device.

Cell Phone Jamming Device

Jamming devices overpower the cell phone by transmitting a signal on the same frequency and at a high enough power that the two signals collide and cancel each other out. Cell phones are designed to add power if they experience low-level interference, so the jammer must recognize and match the power increase from the phone.
Cell phones are full-duplex devices, which means they use two separate frequencies, one for talking and one for listening simultaneously. Some jammers block only one of the frequencies used by cell phones, which has the effect of blocking both. The phone is tricked into thinking there is no service because it can receive only one of the frequencies.
Less complex devices block only one group of frequencies, while sophisticated jammers can block several types of networks at once to head off dual-mode or tri-mode phones that automatically switch among different network types to find an open signal. Some of the high-end devices block all frequencies at once, and others can be tuned to specific frequencies.
To jam a cell phone, all you need is a device that broadcasts on the correct frequencies. Although different cellular systems process signals differently, all cell-phone networks use radio signals that can be interrupted. GSM, used in digital cellular and PCS-based systems, operates in the 900-MHz and 1800-MHz bands in Europe and Asia and in the 1900-MHz (sometimes referred to as 1.9-GHz) band in the United States. Jammers can broadcast on any frequency and are effective against AMPS, CDMA, TDMA, GSM, PCS, DCS, iDEN and Nextel systems. Old-fashioned analog cell phones and today’s digital devices are equally susceptible to jamming.
The actual range of the jammer depends on its power and the local environment, which may include hills or walls of a building that block the jamming signal. Low-powered jammers block calls in a range of about 30 feet (9 m). Higher-powered units create a cell-free zone as large as a football field. Units used by law enforcement can shut down service up to 1 mile (1.6 km) from the device.

Inside Cell Phone Jammers

Electronically speaking, cell-phone jammers are very basic devices. The simplest just have an on/off switch and a light that indicates it’s on. More complex devices have switches to activate jamming at different frequencies. Components of a jammer include:

Antenna

Every jamming device has an antenna to send the signal. Some are contained within an electrical cabinet. On stronger devices, antennas are external to provide longer range and may be tuned for individual frequencies.

Circuitry

The main electronic components of a jammer are:

Voltage-controlled oscillator - Generates the radio signal that will interfere with the cell phone signal
Tuning circuit - Controls the frequency at which the jammer broadcasts its signal by sending a particular voltage to the oscillator
Noise generator - Produces random electronic output in a specified frequency range to jam the cell-phone network signal (part of the tuning circuit)
RF amplification (gain stage) – Boosts the power of the radio frequency output to high enough levels to jam a signal

Power supply

Smaller jamming devices are battery operated. Some look like cell phone and use cell-phone batteries. Stronger devices can be plugged into a standard outlet or wired into a vehicle’s electrical system.

Check your phone - If the battery on your phone is okay, and you’d like to continue your conversation, try walking away from the area. You may be able to get out of the jammer’s range with just a few steps

Cell Phone Jammer Applications

Cell phone jamming devices were originally developed for law enforcement and the military to interrupt communications by criminals and terrorists. The bombs that blew up commuter trains in Spain in March 2004, as well as blasts in Bali in October 2002 and Jakarta in August 2003, all relied on cell phones to trigger explosives. It has been widely reported that a cell-phone jammer thwarted an assassination attempt on Pakistani President Musharraf in December 2003. When President Bush visited London in November 2004, it was reported that British police considered using jammers to protect the president’s motorcade through London.

During a hostage situation, police can control when and where a captor can make a phone call. Police can block phone calls during a drug raid so suspects can’t communicate outside the area. Cell-phone jammers can be used in areas where radio transmissions are dangerous, (areas with a potentially explosive atmosphere), such as chemical storage facilities or grain elevators. The TRJ-89 jammer from Antenna System & Supplies Inc. carries its own electrical generator and can block cellular communications in a 5-mile (8-km) radius.

Corporations use jammers to stop corporate espionage by blocking voice transmissions and photo transmissions from camera phones. On the more questionable end of the legitimacy spectrum, there are rumors that hotel chains install jammers to block guests’ cell-phone usage and force them to use in-room phones at high rates.