With a matching antenna, the FM transmitter circuit shown here can transmit signals up to a range of 2 kilo meters. The transistor Q1 and Q2 forms a classic high sensitive preamplifier stage. The audio signal to be transmitted is coupled to the base of Q1 through capacitor C2. R1, R3, R4, R6, R5 and R9 are the biasing resistors for the preamplifie
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r stage comprising of Q1 and Q2. Transistor Q3 performs the collective job of oscillator, mixer and final power amplifier. C9 and L1 forms the tank circuit which is essential for creating oscillations. Inductor L2 couples the FM signal to the antenna. For L1 make 3 turns of 1mm enamelled copper wire on a 10mm diameter plastic former. On the same core make 2 turns of 1 mm enamelled copper wire close to L1 and that will be L2. Hello Sir, is this circuit has really more than 1 km range with good quality sound and very low noise i tried many different 2km FM transmitter circuit on internet but all of those can not go even 150 meter and also full of noise. so i am afraid. PLEASE HELP ME TO INFORM ME ABOUT THIS CIRCUIT Hi Naren you can use any RH Choke in this place. you can wind around 24 turns of 22swg enemelled copper close wound on 6mm dia self supporting, without any core material(air core)you can wind on a pencil slideout and use. SIR I AM LAXMAN I WANT MAKE A 2KM FM TRANSMITTER. I HAVE SEEN THE CIRCUIT BUT I AM NOT UNDERSTAND WHAT IS L3 THIS IS A COIL AND WHAT IS C9 40PF AND C815PF. THESE ARE PRE SET THIS IS AVALIABLE IN MARKET AND WHAT IS CALL IN MARKET. The negative of the supply should be connected to common line shown as connected to ground. All your components are ok except choke. See my earlier comment. (Hi venkatesh it is an rf choke to prevent rf entering the audio amp stage through power supply. any choke around...
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