WHAT IS A “JAMMER”?
Cell phone jammers are devices that create a temporary “dead zone” to all cell phone traffic
in their immediate proximity. Jammers are typically used by the police and military to control or disrupt communication during hostage situations and bomb threats. Traditionally, jammers were large antennas mounted on trailers that had to be pulled
behind a truck. They now come in a variety of shapes and sizes including models that are
about the size of a cell phone.
JAMMING BASICS.
Disrupting a cell phone is the same as jamming any other type of radio communication. A cell phone works by communicating with its service network through a cell tower or base station. Cell towers divide a city into small areas, or cells. As a cell-phone user drives
down the street, the signal is handed from tower to tower. A jamming device transmits on the same radio frequencies as the cell phone, disrupting the communication between the phone and the cell-phone base station in the tower.
Cell Phone Jammer is an instrument to prevent cellular phone from receiving and transmitting the mobile signals to the base station. Mobile Cell Phone Jammer can block all kinds of mobile phone’s ringing sound at all places such as church, mosque, library, movie theater and meeting room. You just buy it and just attach it at some place. And you will never hear the bell sound of mobile phone any more.
RANGE & FREQUENCY
Most jammers only have a range of about 50 to
80 feet and will only effectively jam your immediate surroundings. Mobile blabber-mouths will just think they’ve hit a dead spot in their cell phone company’s coverage until they leave your jammers immediate vicinity.Stronger jammers are available to cover larger structures like office buildings, movie theaters and churches. They look like a miscellaneous metal boxes with wires sticking out and are usually mounted on walls or ceilings.
Most cell phone jammers come in two versions, one for Europe, North Africa and the Gulf states GSM networks (900 & 1800) and one for the Americas & Canada (800 & 1900mhz) networks.
HOW IT WORKS
Jamming devices overpower the cell phone bytransmitting a signal on the same frequency
and at a high enough power that the twosignals collide and cancel each other out. Cell phones are designed to add power if theyexperience low-level interference, so thejammer must recognize and match the powerincrease from the phone.Cell phones are full-duplex devices i.e. theyuse two separate frequencies, one for talkingand one for listening simultaneously. Some
jammers block only one of the frequency issused by cell phones, which has the effect of
blocking both. The phone is tricked intothinking 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 devicethat 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 a Cell-phone Jammer
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:
1. 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.
2. 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
3. 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.
If network of your phone is jammed, what
should you do?
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.
Analysis:
• Cell phone jammers are devices that
create a temporary “dead zone” to all cell
phone traffic in their immediate proximity.
Jammers are typically used by the police
and military to control or disrupt
communication during hostage situations
and bomb threats. Traditionally, jammers
were large antennas mounted on trailers
that had to be pulled behind a truck. They
now come in a variety of shapes and sizes
including models that are about the size of
a cell phone.
• A jamming device transmits on the same
radio frequencies as the cell phone,
disrupting the communication between the
phone and the cell-phone base station in
the tower.
• 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-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.
