Am fm transmitter

8/27/2016 VATSAL N SHAH 1

Welcome !

Presented By Vatsal ShahIU1241090055

INDUSUNIVERSITY

Electronics & Communication Dept.

5th Semester

PresentationTRANSMITTER

AND

VATSAL N SHAH8/27/2016 2

on


CONTAINT

• Amplitude modulation

• What is Modulation ?

• How does the signal transmitted?

• SIMPLE AM TRANSMITTER CIRCUIT

• ABOUT THE CIRCUIT

• FM Transmitter

• Introduction

• Circuit Diagram

• Working Principle

• Pros & Cons

WHAT IS MODULATION?

Modulation is process of varying one or more properties like frequency , amplitude, phase of

periodic waves.

AM and FM are two very popular and very different methods of sending information over the

airwaves.

Amplitude modulation Frequency modulation

It is modulation frequency of the wave.

This type of transmission is complex.

FM radio ranges in a higher spectrum from 88 to 108 megahertz. (OR) 1200 to 2400 bits per second.

Can send two channels at a time.

It is modulation of amplitude of the wave.

This type of transmission is simple and easily disturbed.

AM radio ranges from 535 to 1705 kilohertz (OR) Up to 1200 Bits per second.

Can send only one channel at a time.


Amplitude Modulation

Amplitude modulation is a technique used in electronic communication, most commonly for

transmitting information via a radio carrier wave.

AM works by varying the strength of the transmitted signal in relation to the information being

sent.

In AM, a radio wave known as the "carrier" or "carrier wave" is modulated in amplitude by the

signal that is to be transmitted.

It is used in both analog and digital communication.

Range of modulator is small as compared to FM.


How does the signal transmitted? This circuit designed to transmit the input signal with the help of a carrier wave.

The input signal is too weak to travel long distance , so we assist a carrier wave to the wave.

Now here we create carrier wave

by the help of RC oscillator in 555

timer chip.

The electrical signals are change

to electromagnetic wave with the

help of antenna.


SIMPLE AM TRANSMITTER CIRCUIT


ABOUT THE CIRCUIT

Potentiometers are commonly used to control electrical devices such as volume controlson audio equipment.

The 555 timer chip makes easy to connect the circuit.

This chip creates the carrier wave of higher frequency.

The audio signal is weak signal which cannot travel long distances . So we assistcarrier wave to carry the our to the destination.



FM Transmitter


Our Model……….

Introduction

The audio of audio devices is converted to FM radio signals by means of FM Transmitter and

then these frequency modulated signals are picked by FM Receivers(radios) and audio can be

then played on receiver.

FM Transmitter is connected to audio output of audio devices.


Circuit Diagram


Components Used

Part Total Qty. Description

C1 1 0.001uf Disc Capacitor

C2 1 5.6pf Disc Capacitor

C3,C4 2 10uf Electrolytic Capacitor

C5 1 3-18pf Adjustable Cap

R1 1 270 Ohm 1/8W Resistor

R2,R5,R6 3 4.7k 1/8W Resistor

R3 1 10k 1/8W Resistor

R4 1 100k 1/8W Resistor

Q1, Q2 2 2N2222A NPN Transistor

L1, L2 2 5 Turn Air Core Coil

MIC 1 Electret Microphone

MISC 19V Battery Snap, PC Board,

. Wire For Antenna



Permanently charged dielectric.

Made by heating a ceramic material, placing it in magnetic field then allowing it to cool while

still in the magnetic field.

Electrostatic equivalent of a permanent magnet.

Sound pressure moves one of its plates.

Movement of the plate changes the capacitance

Connected to an FET amplifier.

These microphones are small, have excellent sensitivity, a wide

frequency response and every low cost.

Electret Microphone


First amplification stage

Standard self-biasing common emitter amplifier.

The 22nF capacitor isolates the microphone from the base voltage of the transistor and only allows

alternating current (AC) signals to pass.

Working Principle

Transmitted signal is Frequency Modulated (FM) which means that the carrier’s amplitude

stays constant and its frequency varies according to the amplitude variations of the audio

signal.

The circuit involves three stages (2 RF stages and one audio preamplifier for the modulation).

The first stage is pre-amplification stage.

The second(RF) stage is an oscillator.

The last (RF) stage is a tuned amplifier that boosts signals from the oscillator.

Use of the additional RF amplifier increases the range of the transmitter.


Pros & Cons

Audio signal can be broadcasted on any FM frequency from 87.5 to 108.0 MHz by this

transmitter.

An FM transmitter can be made to plug into the headphone jack or output port of a

portable audio or video device, such as a CD player, portable media player, or satellite

radio system. The sound is then broadcast through the transmitter, and plays through

an FM broadcast band frequency.

Pros


Pros & Cons Cont.…

But….most devices on the market typically have a short range of up to 100 feet (30 metres) with any average radio (up to about 300 feet (100 metres) with a very good radio under perfect conditions) .

The output power of FM Transmitters is very low so when it comes to use in areas where large number of other radio signals are present. It becomes unsuitable because strong FM signals can bleed over into neighbouring frequencies making the frequencies unusable with the transmitter.

Cons



Engineering

Am fm transmitter