The document discusses amplitude modulation (AM) and frequency modulation (FM) transmitters. It provides a circuit diagram and explanation of a simple AM transmitter that uses a 555 timer chip to generate a carrier wave. It then discusses an FM transmitter circuit, including its components, working principle, and pros and cons. The FM transmitter involves preamplification of an audio signal, oscillation to modulate the signal's frequency, and power amplification of the modulated signal for transmission.

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Welcome !
Presented By Vatsal
Shah
IU1241090055
INDUSUNIVERSITY
Electronics &
Communication Dept.
5th Semester

2. PresentationTRANSMITTER
AND
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on

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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

4. 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.
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5. 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.
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6. 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.
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7. SIMPLE AM TRANSMITTER CIRCUIT
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8. ABOUT THE CIRCUIT
 Potentiometers are commonly used to control electrical devices such as volume controls
on 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 assist
carrier wave to carry the our to the destination.
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FM Transmitter

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Our Model……….

11. 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.
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12. Circuit Diagram
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13. 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 1
9V Battery Snap, PC Board,
. Wire For Antenna
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 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

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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.

16. 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.
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17. 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
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18. 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
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