PHYSICS INVESTIGATORY PROJECT
ACADEMIC YEAR 2025 – 2026
Project:Design and Working of an FM Radio
Transmitter Using Electromagnetic Waves.
Project Mentor: Submitted By: ----------------------
Mr. Madhusoodhanan K
Registration No.
Department of Physics
INDIAN SCHOOL AL SEEB
PC 111, PB 2445, CPO SEEB
Sultanate of Oman
INDIAN SCHOOL AL SEEB
CERTIFICATE
It is hereby certified that
Master/Miss .................................................................................of
class XII Registration No. _______________ has carried out
the necessary Project work in Physics as per the syllabus
prescribed by the Central Board of Secondary Education, New
Delhi for the year 2025-2026.
Mr. Madhusoodhanan
-Physics Teacher
Internal Examiner -
External Examiner-
Date:
School seal: PRINCIPAL
Acknowledgement
It gives me immense pleasure to express deep gratitude to my
esteemed guide Mr. Madhusoodhanan K. Without his keen
interest, limitless patience and enduring guidance, to see me
through, I would not have been able to accomplish this work.
I extend my sincere thanks to this esteemed institution, Indian
School Al Seeb, for nurturing me all these years.
I place on record my heartfelt gratitude to our beloved
Principal Alex C Joseph for creating a conducive learning
environment and being an inspiration, which motivated me to
fulfill my aspirations and achieve my goals.
On a moral personal note, my deepest appreciation to my loving
parents and friends, who put their trust in me and provided me
with unceasing encouragement and support.
_______________________
INDEX
S.No Topic
1 Introduction
2 Theory
3 Application
4 Apparatus
5 Procedure
6 Circuit Diagram
7 Observation Table
8 Result
9 Conclusion
10 Bibliography
🔷 Introduction:
Wireless communication has revolutionized the way we share
information, making it possible to transmit signals over long
distances without physical connections. One of the most widely
used forms of wireless communication is Frequency Modulation
(FM) radio transmission, which operates through the use of
electromagnetic waves. FM transmission plays a vital role in
broadcasting high-fidelity audio signals such as music, speech,
and announcements.
In FM transmission, the frequency of a high-frequency carrier
wave is varied in accordance with the amplitude of the input
audio signal, while the amplitude of the carrier remains constant.
This technique offers significant advantages over Amplitude
Modulation (AM), such as improved sound quality and better
resistance to electrical noise and interference.
An FM transmitter uses components like a microphone,
modulator, oscillator, amplifier, and antenna. The microphone
captures the audio signal, which is then modulated onto a radio-
frequency carrier. The modulated signal is transmitted through the
antenna in the form of electromagnetic waves, which can be
received by FM radios tuned to the same frequency.
This project demonstrates the fundamental working of an FM
transmitter and shows how electromagnetic waves are used to
wirelessly transmit information. It also provides a hands-on
understanding of basic communication concepts and modulation
techniques essential in modern electronics and
telecommunications.
🔷 Theory:
An FM (Frequency Modulation) radio transmitter is a device that
transmits audio signals by varying the frequency of a high-
frequency carrier wave in accordance with the input audio signal.
Unlike amplitude modulation (AM), where the amplitude of the
carrier wave changes, FM changes the frequency of the carrier
wave, resulting in a transmission that is less susceptible to noise
and interference, producing clearer sound quality.
The core of the FM transmitter is an oscillator circuit that
generates a continuous carrier wave, typically in the frequency
range of 88 MHz to 108 MHz, which is the standard FM broadcast
band. This oscillator uses an LC tank circuit, composed of an
inductor (coil) and capacitor connected in parallel, which
determines the resonant frequency based on their values.
When an audio signal from a microphone or other source is
introduced, it modulates the frequency of the carrier wave. This
modulation means the instantaneous frequency of the carrier
wave varies in direct proportion to the amplitude of the input audio
signal. The resulting frequency-modulated wave is then fed to an
antenna, which radiates the electromagnetic waves into the
surrounding environment.
A nearby FM radio receiver tuned to the same frequency can
demodulate the transmitted signal and reproduce the original
audio signal. This project demonstrates fundamental principles of
wave propagation, resonance, oscillations, and frequency
modulation that form the basis of modern wireless
communication.
🔷 Applications of FM Radio Transmitter:
1. Wireless Communication (Short-Range)
FM radio transmitters enable wireless transmission of audio
signals such as voice or music over short distances without the
need for cables. This principle is used in devices like walkie-
talkies, cordless phones, and intercom systems, allowing people
to communicate freely within a limited range, which is very useful
in homes, offices, and industries.
2. Educational Demonstration
Building and studying an FM transmitter helps students grasp
fundamental concepts of physics like electromagnetic wave
propagation, frequency modulation, resonance, and antenna
theory. It acts as a practical tool in laboratories to visually and
audibly demonstrate how wireless communication works in real
life.
3. Mini Radio Broadcasting
Small-scale FM transmitters are used to set up mini radio
stations, especially in schools, colleges, or community centers.
These stations can broadcast educational content, music, news,
or announcements within a limited area, providing a platform for
local communication and entertainment.
4. Testing and Calibration
Low-power FM transmitters are used in electronic and
communication industries to test and calibrate FM radio
receivers. By generating a known frequency signal, they help
ensure radios are tuned correctly and functioning properly before
they reach consumers, improving product reliability.
5. Emergency Communication Systems
In disaster-hit or remote areas where normal communication
infrastructure like mobile networks or internet is unavailable,
simple FM transmitters can be used to broadcast emergency
information and instructions to people. This ensures important
messages reach the public quickly during critical times.
6. Understanding Spectrum Usage
Through this project, students and hobbyists learn about the
allocation and use of radio frequency spectrum, the importance
of avoiding interference, and adhering to legal limits of
transmission power and frequency bands. This understanding is
essential for future careers in electronics and communication
engineering.
7. Remote-Controlled Devices
FM transmitters form the basis for many wireless remote control
systems. Signals transmitted over specific frequencies control
toys, drones, garage doors, and other devices remotely. This
application showcases how wireless signals can be used to
command machines without physical connections.
8. Wireless Microphone Systems
Wireless microphones use FM transmission to send audio
signals from the microphone to a receiver, eliminating the need
for cumbersome cables. This technology is widely used in live
performances, public speaking, broadcasting, and film
production, providing freedom of movement and reducing
setup complexity.
🧪 Apparatus / Materials Required:
Component Quantity
Transistor(2N3904 or 1
BC547)
Capacitors 4-5
(10pF,100nF,etc)
Resistors(1kΩ,10Ω) 2-3
Electret Microphone 1
Copper wire (for 1m
coil,~22AWG)
9v Battery+clip 1
Breadboard or PCB 1
Connecting Wires As needed
Antenna(75cm wire) 1
FM Radio Receiver 1
🔷 Procedure :
1. Collect All Components
Gather the required components: BC547 transistor
(or 2N3904), resistors (1kΩ, 10kΩ), capacitors (10pF–
100nF), electret microphone, 9V battery with clip,
copper wire (for coil and antenna), breadboard or
PCB, and connecting wires.
2. Design the LC Oscillator Circuit
Wind a copper coil (~5 turns on a pen or pencil) to
create an inductor. Connect this coil in parallel with a
small capacitor (~10–20 pF) to form the LC tank
circuit, which will determine the transmitter’s
frequency.
3. Insert the Transistor
Mount the transistor onto the breadboard. Connect
the emitter to ground, the collector to the LC
circuit, and the base to the microphone circuit
through a resistor and capacitor.
4. Connect the Microphone
Attach the electret microphone with proper biasing
(through a resistor ~10kΩ) and coupling capacitor.
This will allow audio signals to pass into the
transistor's base.
5. Build the Modulation Section
Ensure the microphone signal reaches the transistor
base to modulate the carrier frequency generated by
the LC oscillator.
6. Connect the Antenna
Use a ~75 cm insulated wire as the antenna. Attach it
to the collector or output point of the circuit for signal
transmission.
7. Power the Circuit
Connect a 9V battery to the circuit, ensuring correct
polarity. The transmitter should now start oscillating
and modulating.
8. Test with an FM Radio
Turn on a nearby FM radio and slowly tune between
88–108 MHz. Speak into the mic and listen for your
voice.
9. Fine-Tune the Signal
Slightly adjust the coil spacing or capacitor value to
fine-tune the transmission frequency and improve
clarity and range.
CIRCUIT DIAGRAM:
Basic Block:Microphone → Amplifier
(Transistor) → Oscillator (LC Tank) →
Antenna
🔷 Observation Table:
S.No Tuned Audio Clarity of Transmission
Frequency Source Signal Range
(MHz) Type (meters)
1 90.1 Human clear 5
voice
2 92.3 Mobile Slight 6
music distortion
3 95.5 Human Very clear 7
voice
4 98.0 Mobile Noisy 4
music
5 100.2 Human Very clear 6
voice
6 103.6 Mobile Slight
music backgroun
d noise
✅ Result:
The FM Radio Transmitter was successfully constructed
and tested using basic components such as a transistor,
resistors, capacitors, an inductor coil, a microphone, and a
9V battery. The circuit was able to generate a high-
frequency carrier wave and modulate it with an audio
signal through frequency modulation.
By adjusting the LC (inductor–capacitor) tank circuit, the
transmitter was tuned to different frequencies in the FM
band (88–108 MHz). A nearby FM radio receiver was used
to detect and hear the transmitted signal. The audio was
clear and consistent at frequencies like 95.5 MHz and
100.2 MHz, with a maximum range of about 7 meters in
open space.
Slight distortion or background noise occurred at certain
frequencies, which was expected due to limitations in
tuning accuracy and external interference. Overall, the
transmitter performed well within its design limits.
This project effectively demonstrated the principles of
frequency modulation and electromagnetic wave
transmission. It also provided hands-on experience in
circuit construction, testing, and troubleshooting, fulfilling
the project’s objective as a model for short-range wireless
communication.
🔷 Conclusion:
The FM Radio Transmitter project was successfully
completed by constructing a simple circuit using a
transistor, coil, capacitors, and a microphone. The circuit
generated a high-frequency carrier wave that was
modulated by audio signals using frequency modulation
(FM) principles. The transmitter operated within the FM
broadcast band (88–108 MHz) and transmitted clear audio
signals over a short distance of around 5 to 7 meters.
This project helped to understand key concepts like
oscillations, resonance in LC circuits, and frequency
modulation techniques. The ability to tune the transmitter
frequency by adjusting the coil and capacitor
demonstrated the practical application of theoretical
physics concepts.
Despite some minor noise and limited range, the audio
clarity was good, showing FM’s advantage in noise
resistance over amplitude modulation. The project
provided valuable hands-on experience in electronics
assembly, testing, and troubleshooting.
In conclusion, the project successfully demonstrated the
working of an FM transmitter and laid a strong foundation
for learning wireless communication and modern
electronics.
🔷 Bibliography:
1. NCERT. Physics Textbook for Class XII – Part II.
National Council of Educational Research and
Training, 2023.
2. Sedra, Adel S., and Kenneth C. Smith.
Microelectronic Circuits. Oxford University Press, 7th
Edition.
3. Boylestad, Robert L., and Louis Nashelsky. Electronic
Devices and Circuit Theory. Pearson Education.
4. Sharma, Satish K. Basic Electronics: Principles and
Applications. S.K. Kataria & Sons, 2022.
5. Websites:
○ https://www.electronics-tutorials.ws
○ https://www.instructables.com
○ https://www.circuitdigest.com
○ https://en.wikipedia.org/wiki/Frequency_modulati
on
