ElectroMaster

This circuit is a simple two transistor (2N2222) FM transmitter. No license is required for this transmitter according to FCC regulations regarding wireless microphones. If powered by a 9 volt battery and used with an antenna no longer than 12 inches, the transmitter will be within the FCC limits. The microphone is amplified by Q1. Q2, C5, and L1 form an oscillator that operates in the 80 to 130 MHz range. The oscillator is voltage controlled, so it is modulated by the audio signal that is applied to the base of Q2. R6 limits the input to the RF section, and it's value can be adjusted as necessary to limit the volume of the input. L1 and C6 can be made with wire and a pencil. The inductor (L1) is made by winding two pieces of 24 gauge insulated wire, laid side by side, around a pencil six times. Remove the coil you have formed and unscrew the two coils apart from each other. One of these coils (the better looking of the two) will be used in the tank circuit, and the other can be used in the next one you build. The antenna (24 gauge wire) should be soldered to the coil you made, about 2 turns up from the bottom, on the transistor side, and should be 8-12 inches long. To make C6, take a 4 inch piece of 24 gauge insulated wire, bend it over double and, beginning 1/2" from the open end, twist the wire as if you were forming a rope. When you have about 1" of twisted wire, stop and cut the looped end off, leaving about 1/2" of twisted wire (this forms the capacitor) and 1/2" of untwisted wire for leads.

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drrogla

could you transmit a stereo coded signal with this circut?
connect it instead of the mic...

audioguru

C4 in the project has such a high value of 0.1uF that it cuts frequencies above only 1.2KHz. FM stereo needs a response that is flat at 53KHz.

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finhas

very cool one hey create more like this one

rovnex

hey anyone done some TV transmitter yet? im eager to have one.

dfhrace

so why not change the value of C4

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johnzie

do u have a powerful fm transmitter... that can cover a wide place? more or less 500 meters?

wmmullaney

I think you have to have a radio operators licesce...

skydemon2008

May i know how far the signal can be transmitted?

mneary

Give or take, three to five meters. Maybe more, with an open channel and a sensitive receiver.

(This one's a six year old thread.)