CHAPTER ONE

INTRODUCTION

1.1 Introduction

A wireless signal jammer is a device which blocks transmission by

creating interference. This wireless signal jammer can be categorized into

the Radio Frequency (RF) jammer and GSM jammer.

A Radio Frequency jammer is a device used to disrupt or prevent

communication via a broadcasted RF signal. It is an RF and GSM frequency

disrupter commonly known as wideband radio frequency (RF) and GSM

cell phone jammer. Simultaneously they can blocks all commercial FM

broadcast band (87.5 MHz to 108 MHz) and GSM signal transmissions

within the jammer's transmission range. The device can possibly block

these frequencies by transmitting a dirty signal (like noise) on the same

frequency at which the GSM and radio system operates.

A Radio Frequency jammer is a device that transmits a radio

frequency signal on the same frequency at which the radio system

operates and the jamming succeeds when the radio sets in the area where

the jammer is located are disabled.

A GSM jammer is a device that transmits a signal on the same

frequency at which the GSM operates. The jamming succeeds when the

mobile phones in the area where the jammer is located are disabled.

In recent times where bombs are being planted and detonated by

GSM or Radio Frequency signals this device can be at an advantage by

jamming the signals required for the detonation of the bomb.

Presently the mobile jammer devices are becoming civilian products

rather than electronic warfare devices since with the increasing number

of the mobile phone users the need to disable mobile phones in specific

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places where the ringing of cell phone would be disruptive has increased.

These places include worship places university lecture rooms libraries

concert halls meeting rooms and other places where silence is

appreciated.

The solution to these annoying and disrupting noises is to install a

device which can block the signal transmission from mobile phones and

radio sets and thus disrupt the triggering of bombs by these wireless

signals.

1.2 Project Background

The technology being used by this device is very simple. The mobile

phone transmission is being blocked and interfered by RF which creates

high noise. The frequency being generated by the jamming device jams the

signal being generated by the cell tower (as illustrated in figure 1.1 below).

When the signal has been blocked the mobile phone will show “NO

NETWORK” on the network bar and radio devices will not be able to tune

into any signal. Thus all phones and radio devices in the 200m radius of

the jammer will be having the same situation.

Radio Frequency (RF) and Mobile signal jammer is an illegal device

in many countries. It is because the device is blocking the signal which has

been approved by government agency as a legal communication

transmission system. According to the National Communications

Commission (NCC) in Nigeria “The manufacture importation sale or offer

for sale of devices designed to block or jam wireless transmission is

prohibited”. [10]

The reason I am developing this device is for educational purpose

only. This device was developed and tested in this report just for Final

Year Project presentation. There is no intention of manufacturing or

selling such device in Nigeria or elsewhere.

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In the construction of this wireless signal jammer the device will be

able to jam GSM and Radio Frequency (RF) signals and this can be done

alternatively through a switch.

As shown in Fig. 1.1 below the wireless signal jammer is divided

into two major branches: the GSM signal jammer and the radio receiver

jammer. The radio receiver jammer is also sub-divided into the Amplitude

Modulated (AM) signal jammer and the Frequency Modulated (FM) Signal

jammer. The Cell phones and Radio receivers cannot be blocked

simultaneously as they operate at separate frequencies. The frequency can

then be varied using a frequency tuner mounted on the jammer

Fig. 1.1 Block Diagram of Signal Jammer

The block diagram in Fig. 1.2 below gives a pictorial representation

of the working principle of a wireless signal jammer.

RADIO FREQUENCY SIGNAL

JAMMER

RADIO FREQUENCY RECEIVER

SIGNAL JAMMER (87.5-108 MHz)

AMPLITUDE MODULATED SIGNAL

FREQUENCY MODULATED SIGNAL

GSM SIGNAL JAMMER

(935-960MHz)

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Fig. 1.2: Pictorial Representation of a Radio Frequency Jammer

CELL TOWER 1

CELL TOWER 2

CELL TOWER 3

CELL TOWER 4

JAMMER

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MOBILE PHONE

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MOBILE PHONE

RADIO

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From the Fig. 1.2 the jamming device jams cell phones and radio

sets within the range of cell towers 1 and 2.

The cell tower 1 2 3 and 4 transmits signals which can be received

by GSM or radio sets. The jamming device is placed in-between cell towers

1 and 2 and thus produces a signal which is at the same frequency being

operated /transmitted by the cell tower. It can be said that the resultant of

the signals is zero.

From Fig. 1.2 the sending object is the jamming device and the

target object is the cell towers.

However mobile phones placed within the range of cell towers 3

and 4 will not be jammed due to the fact that they are not within the range

of the jamming device.

1.3 Problem Statement

Due to the increasing sophistication and high technology most

people are using mobile phones and also due to the need for man to stay

updated with his environment the use of radio is also in wide use.

Mobile phones have become a very important communication tool

today. With the use of the mobile phones everywhere it becomes

annoying device while working studying praying and many more.

Modern technology has contributed to the sophistication of bombs

which are being triggered by GSM and Radio signals.

Wireless mobile jammer can be placed in schools mosque and

conference hall meeting rooms library and many more places which need

quiet and peaceful environment. This device will block the transmission of

Radio and GSM signals.

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1.4 Objectives

The Development of Wireless Signal Jammer for Security Application

objective is:

 To design Radio Frequency (RF) Intermediate Frequency (IF)

and Power Supply circuit. To construct the Development of

Wireless Signal Jammer for Security Application’s circuit.

 To construct the development of wireless signal jammer for

security application’s circuit.

 To simulate Intermediate Frequency (IF) section circuit.

 To block mobile phones transmission by creating interference.

 To block amplitude modulated and frequency modulated

signal transmission by creating interference within its range.

1.5 Scope of Project /Limitation

This project only focuses on blocking the signal transmission of

GSM900 which is the range between 935 to 960 MHz. This is because the

components are hard to find in Nigeria for the GSM1800 frequency range

between 1805 to 1880 MHz The components for GSM1800 are also very

expensive compared to GSM900.

The second limitations of the project are the device only can block

the three main operators which are ETISALAT MTN and GLOBACOM. This

is because the lines are only for Nigerian users and the frequency band

range is between 935 to 960 MHz. These requirements fulfil the GSM900

specifications.

The third limitation is that for reliability of the jammer a Radio

Frequency amplifier should be incorporated but the components required

for this are difficult to find in Nigeria.

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1.6 Summary

This project is mainly intended to prevent the usage of mobile

phones in places inside it coverage without interfering with

communication channels outside it range thus providing a cheap and

reliable method for blocking mobile communication in the required

restricted area only. Although we must be aware of the fact that nowadays

lot of mobile phones can easily negotiate the jammer effect are available

and therefore advance measures should be taken to jam such type of

devices. The main disadvantage of the mobile phone jammer is that the

transmission of the jamming signal is prohibited by law in many countries.

These disadvantages will restrict the use of Radio Frequency jammer. [10]

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