Indian Institute of Technology Hyderabad FM Transmitter An Independent Project Instructor:-Dr. Kiran Kuchi

 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 reciever.FM Transmitter is connected to audio output of audio devices.

Circuit Diagram

Components used Part Total Qty.Description C uf Disc Capacitor C pf Disc Capacitor C3,C4 2 10uf Electrolytic Capacitor C pf Adjustable Cap R Ohm 1/8W Resistor R2,R5,R k 1/8W Resistor R3 1 10k 1/8W Resistor R k 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

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 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

Thank You  Gaurang Rokad  Shashank Jaiswal Submitted by:-