A mobile phone jammer or signal blocker is an instrument used to prevent cellular phones from receiving signals from base stations. The process of blocking the receiver to receive a transmitted signal is called Jamming of the signal. The jammer effectively disallows cellular phone signal when activated. These devices can be used in practically any location, but are found primarily in places where a phone call would be particularly disruptive because silence is expected. Such places include court rooms, meeting venues, lecture theatres or a library environment.

Mobile phone usage is at the increase and globally appreciated as it made the world a global village. In spite of its advantages, mobile phones are sometimes misused especially in the lecture halls, worship centers, movies theatres, concerts, and shopping malls, all suffer from the spread of cell phones because not all phone users know when to stop talking. These boss serious distractions [1].

Jamming in wireless networks is defined as the disruption of existing wireless communications by decreasing the signal-to-noise ratio at receiver sides through the transmission of interfering wireless signals. Jamming is different from regular network interferences because it describes the deliberate use of wireless signals in an attempt to disrupt communications whereas interference refer to unintentional forms of disruptions. Unintentional interference may be caused by the wireless communications among nodes within the same networks or other devices (e.g. microwave and remote controller). On the other hand, intentional interference is usually conducted by an attacker who intends to interrupt or prevent communications in networks. Jamming can be done at different levels, from hindering transmission to distorting packets in legitimate communications[6].

The concept came into existence through military use when one country during war situation did not want their radio transmission to be intercepted by the enemy, with the use of RF jammers to jam near border areas. Although in most parts of the world, the use is restricted based on specificlaws of the country, application is however allowed for research purposes since these jammers actively broadcast radio signals. One of those attempts led to the creation of radio jammers: in World War II, the British used to jam German radio communications [2, 3, 4].

Jammers work by giving a Radio Frequency (RF) signal or a signal at the same frequency expected by the device that’s being jammed, but at a higher power compared to the targeted signal. The jamming signal itself is usually a random noise. Jammers were originally developed for law enforcement and the military to interrupt communications by criminals and terrorists [5]. The device being jammed will then receive the higher power signal which is from the jammer, and then the devices can no longer function correctly (Bhatia 2015). The technology being used in mobile phone jammers or signal blocker is very simple. It breaks down the network between base station and the cell phone and broadcasts a RF signal with frequency range of cell phones leading to the phone displaying no network available. This device can block the frequency range of 800 to 2100 MHz or the band for which it is designed and a coverage radius of few meters so that it does not disrupt the services of other users.

Mobile phone can be disabled via interrupting any of these signals. Because the distance to the base station is larger than the distance to mobile phone that needs to be blocked, it needs less energy to block signal from base station to phone[7].


Constant interruptions at important gatherings and events as a result of the introduction of mobile communication platform as against the fixed line platform which enables users carry about their mobile phones is increasingly becoming a nuisance when rapt attention or quietness is desired. Modern technology has contributed to the sophistication of bombs which are being triggered by GSM and Radio signals. There is a rising need to use force to prevent cellular and phone-related interruptions. Following the failure of moral suasion and bold inscriptions placed at strategic points and entrances to the venue of events, participants either decide to ignore or completely do not process the instruction appropriately. The need for mobile phone jammers or signal jammer has become imperative to prevent or effectively stop these interruptions by blocking transmission of Radio and GSM signals.

1.3 AIM 

Design and construction of a remote controlled tri–band frequency jammer.


The main objective of this project include:

i. To design a remote control system of  the  circuit

ii. To design Intermediate Frequency (IF) section of the circuit.

iii. To design Radio Frequency (RF) section of the circuit.

iv. To design and construct a wireless signal jammer circuit.

v. To block mobile phone transmission by creating interference within the range of the jammer.


The major significance of this in communication is the reduction in the crime and espionage that are cell phone related such as academic cheating, industrial espionage, privacy invasion, organized theft etc. Although not without its legal issues and downsides, its method of working i.e. the denial of service has been very effective.


This project work presents an operational frequency jammer. Three sections will be designed and integrated to form a complete circuit. The circuit will consist of the IF section, the RF section and power supply unit. The RF section which will consist of the Voltage Controlled Oscillator (VCO) using the ATMEGA328P microcontroller, the RF power amplifier and the antenna. The IF section will generate the tuning signal for the VCO in the RF section which will sweep the desired range of frequencies. The tuning signal will be generated by a triangle wave generator along with a noise generator and then offset by a proper amount so as to sweep the VCO output from the minimum desired frequency to a maximum. The jammer will be designed for fixed use thus taking its power from the regular 220V AC wall outlet. A 5 volt power supply will be designed as the jammer requires different DC input voltages. These components will be selected according to the desired specification such that the frequency range (800MHz to 2100MHz band) and coverage range (10m) is achieved.


The scope of this project is limited to 800MHZ, 188MHZand 2100MHZ withremote controlled systems and remote controlled system it covered 10m. 


Jamming: A radio jammer is any device that deliberately blocks, jams or interferes withauthorized wireless communications. Jamming in wireless networks is defined as the disruptionof existing wireless communications by decreasing the signal-to-noise ratio at receiver sides through the transmission of interfering wireless signals.

1.7.2 Intermediate Frequency: In communications andelectronic engineering, an intermediatefrequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception.

1.7.3 Radio Frequency: Radio frequency (RF) is any of the electromagnetic wave frequencies that liein the range extending from around 3 kHz to 300 GHz, which include those frequencies used for communications or radar signals. RF usually refers to electrical rather than mechanical oscillations. Radiofrequency (RF) energy is another name for radio waves. It is one form ofelectromagnetic energy which consists of waves of electric and magnetic energy moving together (radiating) through space.

1.7.4 Antenna: It is an electrical device which converts electric power into radio waves, and viceversa. It is usually used with a radio transmitter or radio receiver.

1.7.5 Voltage Controlled Oscillator: It is anelectronic oscillatorwhoseoscillation frequencyiscontrolled by a voltage input. The applied input voltage determines the instantaneous oscillation frequency. Consequently, modulating signals applied to control input may cause frequencymodulation (FM) or phase modulation (PM)


This report is structured into five chapters for better understanding of how the aim of the project was achieved. Chapter one gives an introduction to the report stating the significance of the project, aim, objectives, the proposed procedure for carrying out this project work and the way the report is generally presented. Chapter two presents the literature review and the theoretical framework. Chapter three presents the methodology and equations used in the design, simulation and construction. Chapter four presents the results of the design. The findings and conclusion are presented in chapter five.



5.1 Conclusions

This project is very useful for mobile phones restricted places such as private meetings, examination hall, defense establishments, military camp, Hospitals; Petrol pumps, Libraries etc.  This device can scramble/jam mobile devices in a given area within the operating frequency range of   800MHz - 2100MHz at the range of 2-7 meters. The designed device works in Tri-band. It jams the GSM 800 band, GSM 1800 band and the additional UTMS 2100 band. The device was able to jam the four main cell phone carriers in Nigeria: MTN, GLOBACON, AIRTEL and ETISALAT.  

5.2 Challenges

a) The difficulties faced in other to get the required circuit components was really frustrating as most vital components were not readily available locally hence the need to make online orders. 

b) Most online DIY (do it yourself) stores required a MOQ (minimum order quantity) of at least Five piece for some components like Integrated Circuits and in some cases Fifty pieces for discrete components like resistors and capacitors.

c) When the jammer circuit was connected to the remote control circuit, the current required to energize the relay in the remote control circuit was greatly depleted, hence once the relay is in the ON state, it remains ON even when the OFF button on the transmitter is pushed or activated. This was so since the Pole (Common) of the relay requires sufficient amount of current to switch from the NC (Normally Close) to the NO (Normally Open). To remedy the situation, an additional power supply was provided which was gotten from the charger of an old mobile phone. This enables the remote control circuit and the coil of the relay to draw their current from the initially built power supply (POWER 1) while the Jammer section, the Pole and the NO ( Normally Open) terminal of the  relay were connected to the charger of old mobile phone (POWER 2).

5.3 Recommendation 

a) I would recommend the use of Microcontroller based remote control for future work this is due to the challenges faced by Infrared remote control. Infrared remote control 

circuits are easily affected by voltage fluctuations from the power source.

b) Voltage fluctuation can send pulses of signal to the infra-red receiver, which could turn OFF an initially ON device and vice versa hence, an appreciable distance (at least half a meter) should be maintained between the infrared remote controlled circuit and the Mains/Automatic voltage regulators. 

c) Radio Frequency/GSM Jammer can be used to ensure maximum Security and is highly beneficial in a country like Nigeria where in recent times terrorism has become the order of the day and thus, providing an interruption to signals required to detonate bombs and other remote controlled explosives 

d) There are a few improvements that should be done to make the device more compact, stable and efficient:

i. The radius can be made wider by using more robust power amplifiers.

ii. The size of the device can be further reduced by the use of transformerless power supply by employing micro soldering. 

e) The system does not have the capability to sense the presence of mobile devices (mobile detector) which will then initiate the jamming process. Therefore it is expected that future research will consider this area.

f) After blocking GSM 900, DCS (Digital Cellular Systems) 1800, PSC (Personal Communications Services) 1900 and WCDMA 2100 MHZ the next target is blocking of 4G system that is 2400 MHZ

g) The use of mobile phone when driving has increased the rate of auto crash hence a low range jammer whose active region will span around the driver’s seat and the jamming system will operates whenever the driver turns on the ignition should be considered, by so doing all forms of mobile distractions can be avoided. The low range jammer deactivates the driver’s cell phone without affecting other passenger’s cell phones.




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