A

MAJOR PROJECT REPORT

ON
“FM RADIO TRANSMITTER USING ARDUINO”

Submitted in Partial Fulfillment of the Requirment for the Award Diploma

in

ELECTRONIC & TELECOMMUNICATION ENGINEERING

Guided By Under the Supervision of

PROF. GAURAV GUPTA PROF. ASHOK AWASTHI
Lecturer, E.T. Engg. Deptt. Principal G.P.C. Rewa M.P.
G.P.C., Rewa M.P.

Project Coordinated By
PROF. GAURAV GUPTA
Lecturer, E.T. Engg. Deptt.
G.P.C., Rewa

Submitted By

1. Aman Kumar Kushwaha (18106E03007)

2. Vinay Kumar Kushwaha (18106E03059)
3. Vivek Kumar Kushwaha (18106E03062)
4. Pranshu Kushwaha (18106E03032)
5. Ayush Kushwaha (18106E03016)
 DEPARTMENT OF ELECTRONIC & TELECOMMUNICATION

GOVT. POLYTECHNIC COLLAGE REWA (M.P.)

RAJIV GANDHI PROUDYOGIKI VISHWAVIDHYALAYA ,BHOPAL

DEPARTMENT OF ELECTRONIC & TELECOMMUNICATION EGG.

CERTIFICATE

This is certify that the Project Report on

“FM RADIO TRANSMITTER USING ARDUINO”

Student of final year Electronic & Telecommunication Session jan. -jun. 2021
in partial fulfillment o the Requirment of Polytechnic Collage Rewa. He
embodies bonafied work done under my guidance. His work is excellent and
up to our satisfaction. I wish him success in every step of life.

Guided By H.O.D.
PROF. GAURAV GUPTA PROF. V.K. JAIN
Lecturer, E.T. Engg. Deptt. Prof. G.P.C. Rewa
G.P.C., Rewa
 PRINCIPAL
PROF. DR. ASHOK AWASHTHI
G.P.C. REWA (M.P.)

Acknoeledgement
We take great pleasure in expressing my deep sense of

gratitude to our esteemed institution Govt. Polytechnic

Collage Rewa for providing us the opportunity of fulfills

our project.

First of all , we pay our gratitude and regards to our project

coordinator & guide Prof. GAURAV GUPTA Sir for his

valueable acumen support. Many other people have helped

us in the course of preparing this project. We would like

to express our regards to the principle PROF. DR. ASHOK

AWASTHI Sir & the head of department PROF. V.K. JAIN

Sir , for his support.

We are having great pleasure in aknowledgement the

impetus the valueable time spared by our PROF.

JITENDRA KRISHNA ARYA Sir, PROF. HULAS PANDRO

Sir, PROF. PRIYA SHRMA MADAM, PARENTS and

everybody involved in same way other in ameliorating

this project significantly.

Lsatly but certainly not the least we would like thank all

those who helped us during different stages of

competition of this project without it would not have

been possible.
 Condidate Declaration
We hereby declare that the work presented in the project

“FM RADIO TRANSMITTER USING ARDUINO” is

submitted in partial fulfillment of the diplomain E.T.

engineering is an authentic record of our work carried

under the guidance of PROF.GAURAV GUPTA (poject

coordinator) and under the supervision of PROF . DR.

ASHOK AWASTHI (principal) & PROF. V.K. JAIN(H.O.D.)

Govt Polytechnic Collage Rewa (M.P.)

We further declare that this work unique process under

token with the reference of many book.

ALL MEMBERS OF OUR GROUP

1. Aman Kumar Kushwaha (18106E03007)

2. Vinay Kumar Kushwaha (18106E03059)
3. Vivek Kumar Kushwaha (18106E03062)
4. Pranshu Kushwaha (18106E03032)
5. Ayush Kushwaha (18106E03016)
 CONTENT
 INTRODUCTION

 ANTENNA

 MODULATION

 THE COMPONENT WE NEED FOR THIS DEVICE

 METRIAL INTRODUCTION

 CIRCUIT DIAGRAM

 PROGRAM CODE

 FM RADIO TRANSMITTER

 BLOCK DIAGRAM OF FM TRANSMITTER

 WORKING OF FM TRANSMITTER

 ADVANTAGES OF THE FM TRANSMITTER

 DISADVANTAGE OF FM TRANSMITTER

 CONCLUSION
 INTRODUCTION

This Project Report have full information regarding

FM Radio, FM Radio Receiver, Radio Antenna,

Types of modulations, Amplitude Modulation,

Frequency Modulation, Advantages Integrated circuit

and Apparatus required for FM Ratio Receiver

etc.FM Ratio Receiver Project Report. The FM Band

transmission has started very recently in India but its

superior technique and quality has attracted the

listeners.
Unlike AM, the FM is a separate band and its frequency

ranges from 88MHz to 108 MHz. The FM Band can not be

received by the conventional AM receivers. Each and

every AM receiver does not incorporate FM facility. The

present project is a very low cost project and it can be

fitted to any radio receiver/audio system to receive FM

transmission. The circuit of this project is very simple and

can be easily assembled.

Antenna
A theoretical study of radiation from a linear antenna
(length l)

Power radiated a (p/l)2

This implies that for the same antenna length, the power

radiated by short wavelength or high frequency signal

would be large. Hence the effective power radiated by long

wavelength base band signal would be small for a good

transmission, we need high power hence, this also point

out to be need of using high frequency transmission.

Modulation

In amplitude modulated communication, propagation of

radio waves from the transmitting antenna to the receiving

antenna takes place in the following two important ways :

1. Ground Wave Propagation

Ground wave propagation is a type of radio propagation

which is also known as a surface wave. These waves

propagate over the earth’s surface in low and medium

frequencies. These are mainly used for transmission

between the surface of the earth and the ionosphere. These

are made up of the number of constituent waves.

 Ground Wave Propagation

2. Sky Wave Propagation

The transmitted radio waves are supported at their lower

edge by the ground. The radio waves have to be vertically

polarized, so as to prevent the short circuiting of the

electric field component of the wave. The radio wave

induces current in the ground, over which it passes. It

attenuates to some extent due to partial energy absorption

by the ground.
Types of modulations

1. Amplitude Modulation :

In the frequency range 500 kHz. to 30 MHz, amplitude

modulation of the signal is employed and accordingly this

frequency range is termed as amplitude modulated band

(AM bond). The earth’s atmosphere is more or less

transparent to the electromagnetic waves in AM band.

However, the ionosphere (the topmost layer of the

atmosphere) does not allow the electromagnetic waves in

AM band to penetrate it and they are reflected back. When

the frequency of electromagnetic waves is above 40 MHz,

they are no longer reflected by the ionosphere but undergo

refraction. Keeping the above facts in view, the amplitude

modulated signal in medium wave frequency range (up to

1500 kHz.) is transmitted by surface wave propagation or

also called ground wave propagation. In the short wave

frequency range (from a few MHz to 30 MHz), the

amplitude modulated signal is transmitted via reflection

from the ionosphere. It is called sky wave propagation.

2. Frequency Modulation :

For frequencies of electromagnetic waves above 40 MHz,

frequency modulation of the signal is preferred. In the

transmission of TV signals, the frequencies of the

electromagnetic waves
employed ranges from 30 MHz to 1000 MHz. The

transmission of electromagnetic waves in this frequency

range can neither be made by surface wave propagation

nor by sky wave propagation

The component we need for this
devices
1.ARDUINO UNO

2.LCD Nokia 5110 PCD8544

3.FM Transmitter module V1.0 ElecHouse

4.Solderless Jumper Male-Male

5.BreadBoard

6.Potentiometer (50K , 500 Ohm)

7.Battery 9V With Holder

Material Introduction

1.ARDUINO UNO -:
Arduino Uno Rev. 3 Microcontroller Board is based on the

Microchip Technology ATmega328 8-bit Microcontroller

(MCU). Arduino Uno features 14 digital input/output pins

(six of which can be used as PWM outputs), six analog

inputs, and a 16MHz quartz crystal. Uno also includes a

USB connection, a power jack, an In-Circuit Serial

Programming (ICSP) header, and a reset button. This

Arduino MCU board contains everything the user needs to

support the MCU. The user can get started by connecting

the Uno to a computer with the USB cable or by powering

it with an AC/DC adapter or battery. The Uno can be

programmed with Arduino Software (Integrated

Development Environment). The ATmega328 on the Uno

comes preprogrammed with a bootloader that allows the

user to upload new code to the MCU without the use of an

external hardware programmer.

Arduino Uno differs from preceding boards in that it does

not use the FTDI USB-to-serial driver chip. This board

instead features the Atmega16U2 programmed as a USB-

to-serial converter.

FEATURES:-
● Microchip Technology ATmega328 8-Bit AVR
Microcontroller

● 5V operating voltage

● 6V to 20V input voltage (limit)

● 14 (with 6 providing PWM output) digital I/O pins

● Six analog input pins

● 20mA DC current per I/O pin

● 50mA DC current for 3.3V pin

● 32KB Flash memory (ATmega328P)

0.5KB used by bootloader

● 2KB SRAM (ATmega328P)

● 1KB EEPROM (ATmega328P)

● 16MHz clock speed

● 68.6mm x 53.4mm (Length x Width)

● 25g weight

● Powered via USB connection or with external power

supply
○ Power source selected automatically
○
● Includes a number of facilities for communicating with
a computer, another Uno board, or other MCUs
○ ATmega328 provides UART TTL (5V) serial
communication, available on digital pins 0 (RX)
and 1 (TX)
 ■ ATmega16U2 on board channels this serial
communication over USB and appears as
virtual com port to software on the computer

■ 16U2 firmware uses standard USB COM

drivers

■ No external driver needed

➡️Pin discription
Pin Pin Name Details
Category
Power Vin, 3.3V, 5V, Vin: Input voltage to
GND Arduino when using an
external power source.

5V: Regulated power

supply used to power
microcontroller and
other components on
the board.

3.3V: 3.3V supply

generated by on-board
voltage regulator.
Maximum current draw
is 50mA.
 GND: ground pins.
Reset Reset Resets the
microcontroller
Analog Pins A0 – A5 Used to provide analog
input in the range of 0-
5V
Input/Output Digital Pins 0 - Can be used as input or
Pins 13 output pins
Serial 0(Rx), 1(Tx) Used to receive and
transmit TTL serial
data.
External 2, 3 To trigger an interrupt.
Interrupts
PWM 3, 5, 6, 9, 11 Provides 8-bit PWM
output.
SPI 10 (SS), 11 Used for SPI
(MOSI), 12 communication
(MISO) and 13
(SCK)
Inbuilt LED 13 To turn on the inbuilt
LED.
TWI A4 (SDA), A5 Used for TWI
(SCA) communication
AREF AREF To provide reference
voltage for input
voltage.
Arduino Uno Technical Specifications

Microcontroller ATmega328P – 8 bit AVR

family microcontroller
Operating Voltage 5V
Recommended Input 7-12V
Voltage
Input Voltage Limits 6-20V
Analog Input Pins 6 (A0 – A5)
Digital I/O Pins 14 (Out of which 6 provide
PWM output)
DC Current on I/O Pins 40mA
DC Current on 3.3V 50mA
Pin
Flash Memory 32 KB (0.5 KB is used for
Bootloader)
SRAM 2KB
EEPROM 1KB
Frequency (Clock 16MHz
Speed)
Advantages
● Not much knowledge required to get started

● Fairly low cost, depending on shields you need

● Lots of sketches and shields available

● No external programmer or power supply needed

Disadvantages
● No understanding of the AVR microcontroller

● Sketches and shields can be difficult to modify

● No debugger included for checking scripts

● You get no experience of C or professional

development tools.
2. LCD Nokia 5110 PCD8544 -:

Remember the pre-iPhone days when cell phones had

buttons and you only touched that tiny black and white

screen if you needed to clean it? Nokia used these little

LCDs in their 3310 and 5110 cell phones.

As technology changed, these displays finally found their

new place in the world of DIY. Soon they became popular

among hobbyists as these displays are small(only about

1.5″), inexpensive, easy to use, fairly low power and can

display text as well as bitmaps.

PCD8544 LCD Driver

At the heart of the module is a powerful single-chip low

power CMOS LCD driver controller from Philips –

PCD8544.

The chip is designed to drive a graphic display of 84×48

pixels. It interfaces to microcontrollers through a serial bus

interface similar to SPI.

Thanks to the PCD8544 controller’s versatility, it includes

on-chip generation of LCD supply and bias voltages which

results in low power consumption making it suitable for

power sensitive applications. In a normal state, the LCD

consumes as low as 6 to 7mA only.

As per datasheet, this chip operates in the range of 2.7 to

3.3 V and has 3v communication levels. So, for any 5V

logic microcontroller like Arduino, some sort of logic level

shifting is required (otherwise display may get damaged).

LCD Backlight

The LCD also comes with a backlight in different colors

viz. Red, Green, Blue & White.

The backlight is nothing but four LEDs spaced around the

edges of the display.

If you want to change the backlight of the LCD, just

remove the LCD off the board by pushing the metal clips at

the back side. When the screen comes off, you will notice

the four LEDs soldered around the edges of the display.

Just replace the LEDs with desired color LEDs.

Nokia 5110 LCD Display Module Pinout

Before diving into hookup and example code, let’s first take

a look at its Pinout.

Nokia 5110 LCD Module Pinout
Pin Configuration:

RST pin resets the display. It’s an active low pin meaning;

you can reset the display by pulling it low. You can also

connect this pin to the Arduino reset so that it will reset the

screen automatically.

CE(Chip Enable) pin is used to select one of many

connected devices sharing same SPI bus. It’s an active low

pin as well.

D/C(Data/Command) pin tells the display whether the data

it’s receiving is a command or displayable data.

DIN is a serial data pin for SPI interface.

CLK is a serial clock pin for SPI interface.

VCC pin supplies power for the LCD which we connect to

the 3.3V volts pin on the Arduino.

BL(Backlight) pin controls the backlight of the display. To

control its brightness, you can add a potentiometer or

connect this pin to any PWM-capable Arduino pin.

GND should be connected to the ground of Arduino

Wiring Nokia 5110 LCD module with Arduino UNO

3.FM Transmitter module V1.0
ElecHouse

FM transmitter module from elechouse, this board contains

monolithic digital stereo FM transmitter IC KT0803K

which is responsible to make FM over our Audio input and

this IC directly controllable by Arduino board

(Microntrollers) through I2C interface.

Stereo input jack given for audio input from external device

and also this module has on-board mic to pickup our voice.

Audio signal from the mic amplified through 9013 npn

transistor and applied to the tx IC. 32.768 K Crystal

provides clock to this module.

By two wire standard I2C-Microcontrollers can control this

FM module and KT0803K requires no external tuning.

Arduino Hookup-FM transmitter

arduino fm transmitter hookup

Connect the FM transmitter module with Arduino board as

shown in hookup diagram. Here Vcc pin of module

connected to Arduino’s 3.3V power supply pin, and

Ground is connected to GND of Arduino board.

I2C Pins SDA and SCL connected to A4 and A5 of arduino

uno board because these two are I2C pins in uno board. It

change depends on types of arduino board and micro

controllers, check the pin details if other board is used.

Arduino FM transmitter schematic
arduino fm board

It just given for details and connections are made as shown

in the hookup. Any single wire can act as Antenna.

IC KT0803K Block diagram

Monolithic Digital Stereo FM transmitter IC KT0803K

from KTMicro capable of producing 70 MHz – 108 MHz

standard FM with Ultra low power consumption 17mA

operation current from single power supply. By using I2C

wires (SDA, SCL) Micro controller Unit can decide the

channel frequency and control the KT0803K as a slave.

This IC contains on chip 20-bit Audio ADC to convert Left

in, Right in audio into digital signal. On chip DSP core is

well enough to handle the digital audio signals. FM

modulator output is Amplified by RF power amplifier and

bring out to antenna through RF out pin. This IC comes in

16-pin SOP package, operating voltage varies between 1.6

V to 3.6 V and compatible IC for programmable FM

transmission.
4.Solderless Jumper Male-Male

Jumper wires are extremely handy components to have on

hand, especially when prototyping.

Jumper wires are simply wires that have connector pins at

each end, allowing them to be used to connect two points to

each other without soldering. Jumper wires are typically

used with breadboards and other prototyping tools in order

to make it easy to change a circuit as needed. Fairly

simple. In fact, it doesn’t get much more basic than jumper

wires.

What Do the Colors Mean?

Though jumper wires come in a variety of colors, the colors

don’t actually mean anything. This means that a red jumper

wire is technically the same as a black one. But the colors

can be used to your advantage in order to differentiate

between types of connections, such as ground or power.

5. BreadBoard

A breadboard, or protoboard, is a construction base for

prototyping of electronics. Originally the word referred to

a literal bread board, a polished piece of wood used when

slicing bread.[1] In the 1970s the solderless breadboard

(a.k.a. plugboard, a terminal array board) became available

and nowadays the term "breadboard" is commonly used to

refer to these.
Bus and terminal strips:-Solderless breadboards

connect pin to pin by metal strips inside the breadboard.

The layout of a typical solderless breadboard is made up

from two typed of areas, called strips. Strips consist of

interconnected electrical terminals.

Terminal strips

The main areas, to hold most of the electronic components.

In the middle of a terminal strip of a breadboard, one

typically finds a notch running in parallel to the long side.

The notch is to mark the centerline of the terminal strip and

provides limited airflow (cooling) to DIP ICs straddling the

centerline[citation needed]. The clips on the right and left

of

the notch are each connected in a radial way; typically five

clips (i.e., beneath five holes) in a row on each side of the

notch are electrically connected. The five columns on the

left of the notch are often marked as A, B, C, D, and E,

while the ones on the right are marked F, G, H, I and J.

When a "skinny" dual in-line pin package (DIP) integrated

circuit (such as a typical DIP-14 or DIP-16, which have a

0.3-inch (7.6 mm) separation between the pin rows) is

plugged into a breadboard, the pins of one side of the chip

are supposed to go into column E while the pins of the

other side go into column F on the other side of the notch.

The rows are identified by numbers from 1 to as many the

breadboard design goes. Most of the breadboards are

designed to accommodate 17, 30 or 64 rows in the mini,

half, and full configurations respectively.

Solderless breadboard with dual bus strips on both sides

Bus strips
To provide power to the electronic components.

A bus strip usually contains two columns: one for ground

and one for a supply voltage. However, some

breadboards only provide a single-column power

distribution bus strip on each long side. Typically the

row intended for a supply voltage is marked in red,

while
the row for ground is marked in blue or black. Some

manufacturers connect all terminals in a column. Others

just connect groups of, for example, 25 consecutive

terminals in a column. The latter design provides a

circuit designer with some more control over crosstalk

(inductively coupled noise) on the power supply bus.

Often the groups in a bus strip are indicated by gaps in

the color marking.

Bus strips typically run down one or both sides of a

terminal strip or between terminal strips. On large

breadboards additional bus strips can often be found on

the top and bottom of terminal strips.

6. Potentiometer (50K , 500 Ohm)

A potentiometer (also known as a pot or potmeter) is

defined as a 3 terminal variable resistor in which the

resistance is manually varied to control the flow of electric

current. A potentiometer acts as an adjustable voltage

divider.
A potentiometer is a passive electronic component.

Potentiometers work by varying the position of a sliding

contact across a uniform resistance. In a potentiometer, the

entire input voltage is applied across the whole length of

the resistor, and the output voltage is the voltage drop

between the fixed and sliding contact as shown below.A

potentiometer has the two terminals of the input source

fixed to the end of the resistor. To adjust the output voltage

the sliding contact gets moved along the resistor on the

output side.
Characteristics of Potentiometer

The following are the important characteristics of the

potentiometer.

● The potentiometer is very accurate because its works

on the comparing method rather than the deflection

● pointer method for determining the unknown voltages.

● It measures the null or balance point which does not

require power for the measurement.

● The working of the potentiometer is free from the

source resistance because no current flows through the
potentiometer when it is balanced.
Construction of Potentiometer

The construction of the potentiometer is categorised into

two parts. They are the sliding and non-sliding parts. The

sliding contact is a called wiper. The motion of the sliding

contacts is either translatory or rotational. Some

potentiometer uses both the translatory and rotational

motions. Such type of potentiometer uses the resistor in the

form of a helix, and hence they are called heliports.

The potentiometer has three terminals, the two terminals are

connected to the resistor, and the third terminal is

connectedto the wiper which is movable with the wire

Because of this moving wire, the variable potential is

tapped off. The third terminal is used for controlling the

variable resistor. The potential of the third terminal is

controlled by changing the applying potential at the end of

the resistor. The body of the potentiometer is made up of

resistive material, and the wire is wound on it.

Working of Potentiometer

The working principle of the potentiometer is explained

through the circuit shown below. Considers is the switch

used for connecting or disconnecting the galvanometer

from the potentiometer. The battery through the rheostat

and slide wire supply the working current. The working

current may vary by changing the setting of the rheostat.

The method of findings the unknown voltage depends on

the sliding position of the contact at which the

galvanometer shows the zero deflection. The zero or null

deflection of galvanometer shows that the potential of the

unknown source E and the voltage drops E1 across the

sliding wires are equal. Thus, the potential of the unknown

voltage is evaluated by knowing the voltage drop across the

ac portion of the sliding wire.

The slide wire has the uniform cross-section and resistance

across the entire length. As the resistance of the sliding wire

is known, then it is easily controlled by adjusting the

working current. The process of equalising the working

voltage as that of voltage drop is known as

standardisation.
7. Battery 9V With Holder

The nine-volt battery, or 9-volt battery, is a common size of

battery that was introduced for the early transistor radios. It

has a rectangular prism shape with rounded edges and a

polarized snap connector at the top. This type is commonly

used in smoke detectors, gas detectors, clocks, walkie-

talkies, electric guitars and effects units.

Vintage PP3-size 9-volt batteries

Size comparison of batteries: D, C, AA, AAA, AAAA, PP3
(9-volt)The nine-volt battery format is commonly available

in primary carbon-zinc and alkaline chemistry, in primary

lithium iron disulfide, and in rechargeable form in nickel-

cadmium, nickel-metal hydride and lithium-ion. Mercury-

oxide batteries of this format, once common, have not been

manufactured in many years due to their mercury content.

Designations for this format include NEDA 1604 and IEC

6F22 (for zinc-carbon) or MN1604 6LR61 (for alkaline).

The size, regardless of chemistry, is commonly designated

PP3—a designation originally reserved solely for carbon-

zinc, or in some countries, E or E-block.

Circuit diagram

FM transmitter with the help of some popular and

inexpensive components. At the heart of my design is an

NS73M FM Transmitter Breakout Board. It is digitally

tunable from 87 MHz to 108 MHz, and Right and Left

channels are available for stereo broadcast as well.

According to some tutorials, with 2-mW maximum

broadcast power, we’ve been able to transmit up to 60 feet

with a mere 31-inch piece of wire. I tested my prototype to

about 10 feet of distance with a simple 6-inch piece of

22SWG hookup wire as the antenna.

1-NS73M Module

The project is, in fact, a matter of putting together two

highly integrated modules with a tested code snatched from

the web (I still need to bundle it with my own code). Both

of the freestanding modules (NS73MFM transmitter,

Arduino UNO) can be mounted to a breadboard and
interconnected. Refer to the hardware setup and proceed.

The simple code generates digital tones with the Arduino

and broadcasts on Left channel (L) to prove connectivity

and transmission frequency. The hardware shown below is

able to take in stereo audio inputs by performing L+R

channel modulation; i.e., it can work with the typical 3.5-

mm stereo audio jacks of your laptops or smartphones.

However, note that the maximum audio input levels are at

only 200 mV (by raising the volume too high, the audio

may get clipped and you’ll get piteous music at the

receiver side). To transmit audio, just connect the audio

source to LIN, RIN, and GND. Use the same code to set

the broadcast frequency, but omit the tone generation in the

loop function of the given code.
PROGRAM CODE

#include "pitches.h"
int CK = 13; // Clock
int DA = 11; // Data
int LA = 10; // Latch

int AudioPin = 9; // Tone Output

int notes[] = {
NOTE_A4, NOTE_B4, NOTE_C3
};

int numNotes = 3;

void setup() {
Serial.begin(9600);
pinMode(CK, OUTPUT);
pinMode(DA, OUTPUT);
pinMode(LA, OUTPUT);
digitalWrite(LA, LOW); //Unlatch transmitter
delay(100); //Wait
spi_send(0x0E, B00000101); //Software reset
spi_send(0x01, B10110100); //Register 1: forced
subcarrier, pilot tone on
 spi_send(0x02, B00000011); //Register 2: Unlock detect
off, 2mW Tx Power
spi_send(0x03, B10001010); //Register 3: Set broadcast
freq to 97.3, lower byte
spi_send(0x04, B00101110); //Register 4: Set broadcast
freq to 97.3, upper byte
spi_send(0x08, B00011010); //Register 8: set Osc on band
2
spi_send(0x00, B10100001); //Register 0: 200mV audio
input, 75us pre-emphasis on, crystal off, power on
spi_send(0x0E, B00000101); //Software reset
spi_send(0x06, B00011110); //Register 6: charge pumps at
320uA and 80 uA
Serial.print("Transmitting"); //for debugging

void loop() {
// square wave tones
//tone(9, notes[random(numNotes)], 500);
// random frequency
tone(9, random(50, 5000), 20);
delay(10);
}

void spi_send(byte reg, byte data) //Routine to send

Register Address and Data as LSB-first SPI
{
int x;
int n;
digitalWrite(LA, LOW);

for (x = 0 ; x < 4 ; x++) //Send four-bit register

address
{
digitalWrite(CK, LOW); //Toggle the SPI clock
n = (reg >> x) & 1; //n is the xth bit of the register
byte
if (n == 1) {
digitalWrite(DA, HIGH); //Put high bit on SPI data
bus
}
else {
digitalWrite(DA, LOW); //Put low bit on SPI data
bus
}
Serial.print(n);
digitalWrite(CK, HIGH); //Toggle the SPI clock
}

for (x = 0 ; x < 8 ; x++) //Send eight-bit register data

{
digitalWrite(CK, LOW); //Toggle the SPI clock
n = (data >> x) & 1;
 if (n == 1) {
digitalWrite(DA, HIGH); //Put high bit on SPI data
bus
}
else {
digitalWrite(DA, LOW); //Put low bit on SPI data bus
}
Serial.print(n);
digitalWrite(CK, HIGH); //Toggle the SPI clock
}
delayMicroseconds(1); //Wait
digitalWrite(LA, HIGH); //Latch this transfer
delayMicroseconds(4);
digitalWrite(LA, LOW);
digitalWrite(CK, LOW); //Keep CK pin at 0V at
end of data transfer
Serial.print("\n"); // Send new-line to serial for
debugging

As presently configured, the NS73M transmits at 2-mW

power output with a 75-μs pre-emphasis and 100%

modulation to occur at 200 mV of audio input. During

initial power-up, it will start at 97.3 MHz. Fortunately,
everything is reconfigurable, including the FM broadcast

band edges and the channel spacing. You can use this

formula to determine the register values for a new

transmitting frequency (f): (f + 0.304)/0.008192.

Remember to use only the whole number and convert the

result to 16‐bit binary, in which the lower byte goes in

register 3 and the upper byte goes in register 4.

For example:

If 97.3 MHz:
(97.3 + 0.304)/0.008192 = 11,914.55
11,914 = B0010111010001010
Then:
Reg 3 = B10001010
Reg 4 = B00101110
FM RADIO TRANSMITTER:-The FM transmitter

is a single transistor circuit. In the telecommunication, the

frequency modulation (FM) transfers the information by

varying the frequency of the carrier wave according to the

message signal. Generally, the FM transmitter uses VHF

radio frequencies of 87.5 to 108.0 MHz to transmit &

receive the FM signal. This transmitter accomplishes the

most excellent range with less power. The performance and

working of the wireless audio transmitter circuit depend on

the induction coil & variable capacitor. This article will

explain the working of the FM transmitter circuit with its

applications.

Block Diagram of FM Transmitter

The following image shows the block diagram of the FM

transmitter and the required components of the FM

transmitter are; microphone, audio pre-amplifier,

modulator, oscillator, RF- amplifier, and antenna. There are

two frequencies in the FM signal, the first one is the carrier

frequency and the other one is audio frequency. The audio

frequency is used to modulate the carrier frequency. The

FM signal is obtained by differing the carrier frequency by

allowing the AF. The FM transistor consists of the oscillator
to produce the RF signal.

Working of FM Transmitter Circuit

The following circuit diagram shows the FM

transmitter circuit and the required electrical and

electronic components for this circuit is the power

supply of 9V, resistor, capacitor, trimmer capacitor,

inductor, mic, transmitter, and antenna. Let us

consider the microphone to understand the sound

signals and inside the mic, there is a presence of

the capacitive sensor. It produces according to the

vibration to the change of air pressure and the AC

signal.
The formation of the oscillating tank circuit can be done

through the transistor of 2N3904 by using the inductor and

variable capacitor. The transistor used in this circuit is an

NPN transistor used for general purpose amplification. If

the current is passed at the inductor L1 and variable

capacitor then the tank circuit will oscillate at the resonant

carrier frequency of the FM modulation. The negative

feedback will be the capacitor C2 to the oscillating tank

circuit.

To generate the radio frequency carrier waves the FM

transmitter circuit requires an oscillator. The tank circuit is

derived from the LC circuit to store the energy for

oscillations. The input audio signal from the mic penetrated

to the base of the transistor, which modulates the LC tank

circuit carrier frequency in FM format. The variable

capacitor is used to change the resonant frequency for fine

modification to the FM frequency band. The modulated

signal from the antenna is radiated as radio waves at the

FM frequency band and the antenna is nothing but copper

wire of 20cm long and 24 gauge. In this circuit, the length

of the antenna should be significant and here you can use

the 25-27 inches long copper wire of the antenna.

Application of Fm TransmitterThe FM transmitters are used

in the homes like sound systems in halls to fill the sound

with the audio source.

These are also used in cars and fitness centers.

The correctional facilities have used in the FM transmitters

to reduce the prison noise in common areas.

Advantages of the FM Transmitters

● The FM transmitters are easy to use and the price is

low
● The efficiency of the transmitter is very high
● It has a large operating range
● This transmitter will reject the noise signal from an
amplitude variation.
●
Disadvantages of the FM Transmitter

● In the FM transmitter, the huge wider channel is

required.
● The FM transmitter and receiver will tend to be more
complex.
● Due to some interference, there is poor quality in the
received signals

 Conclusion :-We therefore conclude that this

project is indeed suitable for Electronics Engineering

students especially to students taking up FM

Transmission and Reception in their Electronic

Communications Theory subject. By accomplishing

this project,we now appreciate the theory

more.Through this project, we have now seen an exact

application of our lessons such as Wireless

communication, FM modulation, transmission,

demodulation, reception, and also oscillators,

amplifiers, and more.Being able to transmit and

receive information by means of wireless FM

communication is indeed fascinating.