Minor Project Report

UNIVERSITY INSTITUTE OF ENGG. & TECHNOLOGY

KURUKSHETRA UNIV. KURUKSHETRA

MINOR PROJECT

ON

‘FM JAMMER’

SUBMITTED TO: SUBMITTED BY:

Ms. Bharti Mahajan Surbhi Gulati (2507022)Lect. U.I.E.T Manoj Kumar(2507039)

K.U.K Manvir Singh (2507030) IVth Yr.

ELEC. & COMM.

CONTENTS

1. INTRODUCTION2. OBJECTIVES TO BE ACHIEVED 3. CIRCUIT DIAGRAM

4. PRINCIPLE OF OPERATION4.1 Radiation of electromagnetic energy4.2 Calculation4.3 FM modulation characteristics4.4 Applications

5. DESCRIPTION OF COMPONENTS USED5.1 Transistor

5.1.1 Transistor 2N22225.2 Variable capacitor5.3 Inductor5.4 Capacitor

6. WHAT HAVE WE DONE?7. APPLICATIONS8. BIBLIOGRAPHY

ACKNOWLEDGEMENT

We are fortunate enough to work on our minor project on FM Jammer simulation & designing. We take this opportunity to thank all those people who helped us in successful completion of our minor project and helped us in learning a lot of new things and meeting people whose thoughts and insight helped us in increasing our knowledge and understanding.

We specially thank the U.I.E.T. ECE faculty for their support in completion of our project, especially Er. BHARTI MAHAJAN, Lect. U.I.E.T, ECE Deptt. who was constant source of inspiration for us and encouraged us to complete this task with her unrelenting support and very useful guidance.

Without her support, it would have been very difficult to successfully complete this project.

Surbhi Gulati

Manoj Kumar

Manvir Singh

CERTIFICATE

This is to certify that the undersigned students have completed the minor project on ‘FM Jammer’ under my guidance. They worked hard for the successful completion of the project. I wish them all the best for future.

(Bharti Mahajan) Surbhi Gulati

Manoj Kumar

Manvir Singh

FM JAMMER

INTRODUCTION :

FM JAMMER can be used to jam FM radios in its vicinity. The circuit is nothing but a classic single transistor oscillator operating in the VHF region. Working principle of the circuit is very simple and straight forward. Powerful VHF oscillations from the circuit will interfere with the FM signals to nullify it. Jammer circuits like this are illegal in many countries.

OBJECTIVES to be achieved :

Software implementation :Under this, we will design and test the circuit of an FM Jammer using Multisim software and observe the output waveform to check if it will produce waveforms of desired frequency range, so that it can interfere with the transmitted FM signal and block it completely.

Hardware implementation :Next , we will design the circuit on a Printed Circuit Board

(PCB) to obtain a working model for demonstration.

CIRCUIT DIAGRAM:

Components required:

1. Transistor - 2N22222. Inductor (1) – any value in milliHenry3. Capacitors (3) – 0.01uf, 10uf, 6pf4. Variable capacitor (1) – 6-35pf5. Power supply – 9V6. Resistors (3) – 15K, 3.9K,220 (all values in Ohms)

PRINCIPLE OF OPERATION:

RADIATION OF ELECTROMAGNETIC ENERGYThe electromagnetic radiation from an antenna is made up of two components, the E field and the H field. We discussed these fields in chapters 1 and 2. The two fields occur 90 degrees out of phase with each other. These fields add and produce a single electromagnetic field. The total energy in the radiated wave remains constant in space except for some absorption of energy by the Earth. However, as the wave advances, the energy spreads out over a greater area and, at any given point, decreases as the distanceincreases.Various factors in the antenna circuit affect the radiation of these waves. In figure , for example, if an alternating current is applied at the A end of the length of wire from A to B, the wave will travel along the wire until it reaches the B end. Since the B end is free, an open circuit exists and the wave cannot travel farther. This is a point of high impedance. The wave bounces back (reflects) from this point of high impedance and travels toward the starting point, where it is again reflected. The energy of the wave would be gradually dissipated by the resistance of the wire of this back-and-forth motion (oscillation); however, each time it reaches the starting point, the wave is reinforced by an amount sufficient to replace the energy lost. This results in continuous oscillations of energy along the wire and a high voltage at the A end of the wire. These oscillations are applied to the antenna at a rate equal to the frequency of the rf voltage.

These impulses must be properly timed to sustain oscillations in the antenna. The rate at which the waves travel along the wire is constant at approximately 300,000,000 meters per second. The length of the antenna must be such that a wave will travel from one end to the other and back again during the period of 1 cycle of the rf voltage. Remember, the distance a wave travels during the period of 1 cycle is known as the wavelength and is found by dividing the rate of travel by the frequency.Look at the current and voltage (charge) distribution on the antenna in figure 4-6. A maximum movement of electrons is in the center of the antenna at all times; therefore, the center of the antenna is at a low impedance. This condition is called a STANDING WAVE of current. The points of high current and high voltage are known as current and voltage LOOPS. The points of minimum current and minimum voltage are known as current and voltage NODES. View A shows a current loop and current nodes. View B shows voltage loops and a voltage node. View C shows the resultant voltage and current loops andnodes. The presence of standing waves describes the condition of resonance in an antenna. At resonance the waves travel back and forth in the antenna reinforcing each other and the electromagnetic waves are transmitted into space at maximum radiation. When the antenna is not at resonance, the waves tend to cancel each other and lose energy in the form of heat.

Resonant frequency can be calculated with the following formula:

Calculation:

L=1mH

C=2.5pF

f =1÷ (2 π √10−6 ¿2.5∗10−12 )

f =1÷(2π∗1.54∗10−9)

f =1÷ ( 2∗3.14∗1.54∗10−9 )

f =100 MHz

FM Modulation characteristics

Frequency modulation (FM) is a form of modulation which conveys information over a carrier wave by varying its frequency (contrast this with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant). In analog applications, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal. This form of modulation is commonly used in the FM broadcast band.

Applications:

BroadcastingFM broadcasting is a broadcast technology pioneered by Edwin Howard Armstrong that uses frequency modulation (FM) to provide high-fidelity sound over broadcast radio.

FM is commonly used at VHF radio frequencies for high-fidelity broadcasts of music and speech (see FM broadcasting). Normal (analog) TV sound is also broadcast using FM. A narrow band form is used for voice communications in commercial and amateur radio settings. The type of FM used in broadcast is generally called wide-FM, or W-FM. In two-way radio, narrowband narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into space.

Broadcast bands

Throughout the world, the broadcast band falls within the VHF part of the radio spectrum. Usually 87.5 to 108.0 MHz is used, or some portion thereof, with few exceptions:

Magnetic Tape Storage

FM is also used at intermediate frequencies by all analog VCR systems, including VHS, to record both the luminance (black and white) and the chrominance portions of the video signal. FM is the only feasible method of recording video to and retrieving video from Magnetic tape without extreme distortion, as video signals have a very large range of frequency components — from a few hertz to several megahertz, too wide for equalizers to work with due to electronic noise below −60 dB. FM also keeps the tape at saturation level, and therefore acts as a form of noise reduction, and a simple limiter can mask variations in the playback output, and the FM capture effect removes print-through and pre-echo. A continuous pilot-tone, if added to the signal — as was done on V2000 and many Hi-band formats — can keep mechanical jitter under control and assist timebase correction.

These FM systems are unusual in that they have a ratio of carrier to maximum modulation frequency of less than two; contrast this with FM audio broadcasting where the ratio is around 10,000. Consider for example a 6 MHz carrier modulated at a 3.5 MHz rate; by Bessel analysis the first sidebands are on 9.5 and 2.5 MHz, while the second sidebands are on 13 MHz and −1 MHz. The result is a sideband of reversed phase on +1 MHz; on demodulation, this results in an unwanted output at 6−1 = 5 MHz. The system must be designed so that this is at an acceptable level.

Sound

FM is also used at audio frequencies to synthesize sound. This technique, known as FM synthesis, was popularized by early digital synthesizers and became a standard feature for several generations of personal computer sound cards.

An audio signal (top) may be carried by an AM or FM radio wave.

Radio

Edwin Howard Armstrong (1890–1954) was an American electrical engineer who invented frequency modulation (FM) radio. He patented the regenerative circuit in 1914, the superheterodyne receiver in 1918 and the super-regenerative circuit in 1922. He presented his paper: "A Method of Reducing Disturbances in Radio Signaling by a System of Frequency Modulation", which first described FM radio, before the New York section of the Institute of Radio Engineers on November 6, 1935. The paper was published in 1936.[6]

As the name implies, wideband FM (W-FM) requires a wider signal bandwidth than amplitude modulation by an equivalent modulating signal, but this also makes the signal more robust against noise and interference. Frequency modulation is also more robust against simple signal amplitude fading phenomena. As a result, FM was chosen as the modulation standard for high frequency, high fidelity radio transmission: hence the term "FM radio" (although for many years the BBC called it "VHF radio", because commercial FM broadcasting uses a well-known part of the VHF band -- the FM broadcast band.

FM receivers employ a special detector for FM signals and exhibit a phenomenon called capture effect, where the tuner is able to clearly receive the stronger of two stations being broadcast on the same frequency. Problematically however, frequency drift or lack of selectivity may cause one station or signal to be suddenly overtaken by another on an adjacent channel. Frequency drift typically constituted a problem on very old or inexpensive receivers, while inadequate selectivity may plague any tuner.

An FM signal can also be used to carry a stereo signal: see FM stereo. However, this is done by using multiplexing and demultiplexing before and after the FM process. The rest of this article ignores the stereo multiplexing and demultiplexing process used in "stereo FM", and concentrates on the FM

modulation and demodulation process, which is identical in stereo and mono processes.

A high-efficiency radio-frequency switching amplifier can be used to transmit FM signals (and other constant-amplitude signals). For a given signal strength (measured at the receiver antenna), switching amplifiers use less battery power and typically cost less than a linear amplifier. This gives FM another advantage over other modulation schemes that require linear amplifiers, such as AM and QAM.

DESCRIPTION OF COMPONENTS USED

1. Transistor

Introduction:

· The transistor is a semiconductor device than can function as a signal amplifier or as a solid-state switch. A typical switching circuit using a PNPtransistor is shown at the left.· In a transistor a very small current input signal flowing emitter-to-base is able to control a much larger current which flows from the system powersupply, through the transistor emitter-to-collector,through the load, and back to the power supply.· In this example the input control signal loop is shown in red and the larger output current loop is shown in blue. With no input the transistor will beturned OFF (cutoff) and the relay will be dropped out. When the low-level input from the PLC microprocessor turns the transistor ON (saturates)current flows from the power supply, through the transistor, and picks the relay.

Transistor Packages

There are many transistor case designs. Some conform to JEDEC Standards and are defined by Transistor Outline (TO) designations. Several case designs are illustrated below. Solid -state devices other than transistors are also housed in

these same packages. In general, the larger the unit, the greater the current or power rating of the device.

IntroductionThere are three main classifications of transistors each with its own symbols, characteristics, design parameters, and applications. See below and the following pages for additional details and applications on each of thesetransistor types. Several special-function transistor types also exist which do not fall into the categories below,such as the unijunction (UJT) transistor that is used for SCR firing and time delay applications. These specialfunctiondevices are described separately.

· Bipolar transistors are considered current driven devices and have a relatively low input impedance. They are available as NPN or PNP types. The designation describes the polarity of the semiconductor material used to fabricate the transistor.

· Field Effect Transistors, FET’s, are referred to as voltage driven devices which have a high input impedance.Field Effect Transistors are further subdivided into two classifications: 1) Junction Field Effect Transistors, or JFET’s, and 2) Metal Oxide Semiconductor Field Effect Transistors or MOSFET’s.

· Insulated Gate Bipolar Transistors, known as IGBT’s, are the most recent transistor development. This hybrid device combines characteristics of both the Bipolar Transistor with the capacitive coupled, high impedance input, of the MOS device

.

Transistor testing

PNP Test Procedure· Connect the meter leads with the polarity as shown and verify thatthe base-to-emitter and base-tocollector junctions read as a forwardbiased diode: 0.5 to 0.8 VDC.· Reverse the meter connections to the transistor and verify that bothPN junctions do not conduct. Meter should indicate an opencircuit. (Display = OUCH or OL.)· Finally read the resistance from emitter to collector and verify anopen circuit reading in both directions. (Note: A short can existfrom emitter to collector even if the individual PN junctions test properly.)

NPN Test Procedure· Connect the meter leads with the polarity as shown and verify thatthe base-to-emitter and base-tocollector junctions read as a forwardbiased diode: 0.5 to 0.8 VDC.· Reverse the meter connections to the transistor and verify that bothPN junctions do not conduct. Meter should indicate an open circuit. (Display = OUCH or OL.)· Finally read the resistance from emitter to collector and verify anopen circuit reading in both directions.(Note: A short can exist from emitter to collector even ifthe individual PN junctions test properly.)

Transistor 2N2222:The 2N2222, often referred to as the 'quad two' transistor, is a small, common NPN BJT transistor used for general purpose low-power amplifying or switching applications.

It is designed for low to medium current, low power, medium voltage, and can operate at moderately high speeds. It was originally made in the TO-18 metal can as shown in the picture, but is more commonly available now in the cheaper TO-92 packaging, where it is known as the PN2222 or P2N2222

All variations have a beta or current gain (hFE) of at least 100 in optimal conditions. It is used in a variety of analog amplification and switching applications.

It is available in a variety of small through-hole and surface mount packages including TO-92, SOT-23, and SOT-223.

2. Variable capacitor

A variable capacitor is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. Variable capacitors are often used in L/C circuits to set the resonance frequency, e.g. to tune a radio (therefore they are sometimes called tuning capacitors), or as a variable reactance, e.g. for impedance matching in antenna tuners.

TYPES:

Mechanically controlled:

In mechanically controlled variable capacitors, the distance between the plates, or the amount of plate surface area which overlaps, can be changed.

The most common form arranges a group of semicircular metal plates on a rotary axis (“rotor”) that are positioned in the gaps between a set of stationary plates (“stator”) so that the area of overlap can be changed by rotating the axis. Air or plastic foils can be used as dielectric material. By choosing the shape of the rotary plates, various functions of capacitance vs. angle can be created, e.g. to obtain a linear frequency scale. Various forms of reduction gear mechanisms are often used to achieve finer tuning control, i.e. to spread the variation of capacity over a larger angle, often several turns. A vacuum variable capacitor uses a set of plates made from concentric cylinders that can be slid in or out of an opposing set of cylinders[1] (sleeve and plunger). These plates are then sealed inside of a non-conductive envelope such as glass or ceramic and placed under a high vacuum. The movable part (plunger) is mounted on a flexible metal membrane that seals and maintains the vacuum. A screw shaft is attached to the plunger, when the shaft is turned the plunger moves in or out of the sleeve and the value of the capacitor changes. The vacuum not only increases the working voltage and current handling capacity of the capacitor it also greatly reduces the chance of arcing across the plates. The most common usage for vacuum variables are in high powered transmitters such as those used for broadcasting,

military and amateur radio as well as high powered RF tuning networks. Vacuum variables can also be more convenient since the elements are under a vacuum the working voltage can be higher than an air variable the same size, allowing the size of the vacuum capacitor to be reduced.

Very cheap variable capacitors are constructed from layered aluminium and plastic foils that are variably pressed together using a screw. These so-called squeezers can’t provide a stable and reproducible capacitance, however. A variant of this structure that allows for linear movement of one set of plates to change the plate overlap area is also used and might be called a slider. This has practical advantages for makeshift or home construction and may be found in resonant loop antennas or crystal radios.

Small variable capacitors operated by screwdriver (for instance, to precisely set a resonant frequency at the factory and then never be adjusted again) are called trimmer capacitors. In addition to air and plastic, trimmers can also be made using a ceramic dielectric.

Electronically controlled:

The thickness of the depletion layer of a reverse-biased semiconductor diode varies with the DC voltage applied across the diode. Any diode exhibits this effect (including p/n junctions in transistors), but devices specifically sold as variable capacitance diodes (also called varactors or varicaps) are designed with a large junction area and a doping profile specifically designed to maximize capacitance.

Their use is limited to low signal amplitudes to avoid obvious distortions as the capacitance would be affected by the change of signal voltage, precluding their use in the input stages of high-quality RF communications receivers, where they would add unacceptable levels of intermodulation. At VHF/UHF frequencies, e.g. in FM Radio or TV tuners, dynamic range is limited by noise rather than large signal handling requirements, and varicaps are commonly used in the signal path.

Varicaps are used for frequency modulation of oscillators, and to make high-frequency voltage controlled oscillators (VCOs), the core component in phase-locked loop (PLL) frequency synthesizers that are ubiquitous in modern communications equipment.

Digitally Tuned Capacitor:

A digitally tuned capacitor is a type of chip-form variable capacitor patented by Peregrine Semiconductor in the form of DuNE™ technology using UltraCMOS™ process and HaRP™ design innovation.. The DuNE digitally tunable capacitor (DTC) chip contains five capacitors switched by MOSFETs that operate from a serial input bus with a 5-bit code providing 32 possible capacitor values.

The capacitor values can range from 0.5 to 10 pF with typical tuning ratios of 3:1 to 6:1, or 10:1 in some cases. Typical switching speed is less than 5 µs. Capacitor Q's greater than 100 are possible. The frequency range is up to 3 GHz, and power handling is up to 40 dBm. The chip operates with a supply voltage of 2.4 to 3.0 V with current consumption in the 20- to 100-µA range, unlike others . The device comes in a 2- by 2-mm dual flat no-lead (DFN) 8L flip-chip or plastic package.

It is intended for antenna impedance matching in multi-band GSM/WCDMA cellular handsets and mobile TV recivers that must operate over wide frequency ranges such as the European DVB-H and Japanese ISDB-T mobile TV systems, due to its small size, high Q factor, low voltage operation and current consumption.

Transducers

Variable capacitance is sometimes used to convert physical phenomena into electrical signals.

In a capacitor microphone (commonly known as a condenser microphone), the diaphragm acts as one plate of a capacitor, and vibrations produce changes in the distance between the diaphragm and a fixed plate, changing the voltage maintained across the capacitor plates.

Some types of industrial sensors use a capacitor element to convert physical quantities such as pressure, displacement or relative humidity to an electrical signal for measurement purposes.

Capacitive sensors can also be used in the place of switches, e.g. in computer keyboards or “touch buttons” for elevators that have no movable parts.

3. INDUCTOR

An inductor or a reactor is a passive electrical component that can store energy in a magnetic field created by the electric current passing through it. An inductor's ability to store magnetic energy is measured by its inductance, in units of henries. Typically an inductor is a conducting wire shaped as a coil, the loops helping to create a strong magnetic field inside the coil due to Ampere's Law. Due to the time-varying magnetic field inside the coil, a voltage is induced, according to Faraday's law of electromagnetic induction, which by Lenz's Law opposes the change in current that created it. Inductors are one of the basic electronic components used in electronics where current and voltage change with time, due to the ability of inductors to delay and reshape alternating currents. Inductors called chokes are used as parts of filters in power supplies or to block AC signals from passing through a circuit.

Overview

Inductance (L) results from the magnetic field forming around a current-carrying conductor which tends to resist changes in the current. Electric current through the conductor creates a magnetic flux proportional to the current, and a change in this current creates a corresponding change in magnetic flux which, in turn, by Faraday's Law generates an electromotive force (EMF) that opposes this change in current. Inductance is a measure of the amount of EMF generated per unit change in current. For example, an inductor with an inductance of 1 henry produces an EMF of 1 volt when the current through the inductor changes at the rate of 1 ampere per second. The number of loops, the size of each loop, and the material it is wrapped around all affect the inductance. For example, the magnetic flux linking these turns can be increased by coiling the conductor around a material with a high permeability such as iron. This can increase the inductance by 2000 times.

Applications

Inductors are used extensively in analog circuits and signal processing. Inductors in conjunction with capacitors and other components form tuned circuits which can emphasize or filter out specific signal frequencies. Applications range from the use of large inductors in power supplies, which in conjunction with filter capacitors remove residual hums known as the mains hum or other fluctuations from the direct current output, to the small inductance of the ferrite bead or torus installed around a cable to prevent radio frequency interference from being transmitted down the wire. Smaller inductor/capacitor combinations provide tuned circuits used in radio reception and broadcasting, for instance.

In electric circuits

The effect of an inductor in a circuit is to oppose changes in current through it by developing a voltage across it proportional to the rate of change of the current. An ideal inductor would offer no resistance to a constant direct current; however, only superconducting inductors have truly zero electrical resistance.

The relationship between the time-varying voltage v(t) across an inductor with inductance L and the time-varying current i(t) passing through it is described by the differential equation:

When there is a sinusoidal alternating current (AC) through an inductor, a sinusoidal voltage is induced. The amplitude of the voltage is proportional to the product of the amplitude (IP) of the current and the frequency (f) of the current.

In this situation, the phase of the current lags that of the voltage by π/2.If an inductor is connected to a direct current source with value I via a resistance R, and then the current source is short-circuited, the differential relationship above shows that the current through the inductor will discharge with an exponential decay.

4. Capacitor

A capacitor is a passive electronic component consisting of a pair of conductors separated by a dielectric (insulator). When there is a potential difference (voltage) across the conductors, a static electric field develops in the dielectric that stores energy and produces a mechanical force between the conductors. An ideal capacitor is characterized by a single constant value, capacitance, measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them.

Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass, in filter networks, for smoothing the output of power supplies, in the resonant circuits that tune radios to particular frequencies and for many other purposes.

The effect is greatest when there is a narrow separation between large areas of conductor, hence capacitor conductors are often called "plates", referring to an early means of construction. In practice the dielectric between the plates passes

a small amount of leakage current and also has an electric field strength limit, resulting in a breakdown voltage, while the conductors and leads introduce an undesired inductance and resistance.

Parallel plate model

Dielectric is placed between two conducting plates, each of area A and with a separation of d.

The simplest capacitor consists of two parallel conductive plates separated by a dielectric with permittivity ε (such as air). The model may also be used to make qualitative predictions for other device geometries. The plates are considered to extend uniformly over an area A and a charge density ±ρ = ±Q/A exists on their surface. Assuming that the width of the plates is much greater than their separation d, the electric field near the centre of the device will be uniform with the magnitude E = ρ/ε. The voltage is defined as the line integral of the electric field between the plates

Solving this for C = Q/V reveals that capacitance increases with area and decreases with separationThe capacitance is therefore greatest in devices made from materials with a high permittivity.

Capacitor markings

Most capacitors have numbers printed on their bodies to indicate their electrical characteristics. Larger capacitors like electrolytics usually display the actual capacitance together with the unit (for example, 220 μF). Smaller capacitors like ceramics, however, use a shorthand consisting of three numbers and a letter, where the numbers show the capacitance in pF (calculated as XY x 10Z for the numbers XYZ) and the letter indicates the tolerance (J, K or M for ±5%, ±10% and ±20% respectively).

Additionally, the capacitor may show its working voltage, temperature and other relevant characteristics.

Example:

A capacitor with the text 473K 330V on its body has a capacitance of 47 x 103 pF = 47 nF (±10%) with a working voltage of 330 V.

WHAT HAVE WE DONE?

We have:

i.made our own inductor for the project. This inductor has a value falling in microhenry range. For this, we took 16 AWG enamelled copper wire and wound it on a 9 mm former, giving it 6 turns in total. Then we removed the former and obtained an inductor of desired value.

ii.implemented the circuit on multisim. We designed the circuit on Multisim software, gave the components the required values and tested it for proper functioning. Next, we observed the output waveforms being transmitted from the inductor. The circuit designed and the output waveform produced are shown below:

iii.designed the circuit on a PCB. Then, we realised the whole circuit physically to see its practical working. For this, we used a Printed Circuit Board and joined the various components on the PCB with a connecting wire using soldering.

Points to be kept in mind:

For L1 make 6 turns of 16AWG enamelled copper wire on a 9mm plastic former.

The circuit can be powered using a 9V PP3 battery. For extended range, use an antenna. A 30cm long wire connected anywhere on the coil will do for the antenna. For better performance, assemble the circuit on a good PCB.

Modus Operandi:

This circuit simply generates VHF (Very High Frequency) waves .

These waves interfere with the FM waves being transmitted.

This interference is destructive in nature and thus the FM waves are blocked.

APPLICATIONS AND SCOPE OF FURTHER DEVELOPMENT:

Can be used to block FM signals in places where FM signals are not desired. For eg. i. In libraries

ii. For Military usage iii. Offices and educational institutes

Its range can be increased by connecting a wire of any length with the inductor.

In future, with advancement in technology, its range can be increased drastically and we can also use it for blocking waves other than FM, such as Amplitude Modulated waves.

BIBLIOGRAPHY

i. Circuit Diagram-www.circuitstoday.comii. www.wikipedia.com

iii. Parallel LC Circuits-‘Electrical Engineering’ by Sahdev