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The Simplest FM Transmitter Ever Made |
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This is the most simple and cheap FM transmitter you can ever find. This circuit is really cool. This runs at very low voltage, by a CR2025 3V battery, current consumption is also low.And the total size of this FM transmitter (including battery, excluding antenna) is less than that of a matchbox. The circuit has a central RF oscillator NPN transistor BF494 (substitute: BF199). A coil takes care of the output frequency. It consists of 36SWG wire 2.5 turns only in 5mm diameter ferrite rod. Keep the circuit as small as possible. Try to use no wires in the main functional area (transistor and coil). The input from the audio output of computer / PMP / mobile is given to the biased base of the transistor. The transistor gives a RF humming accordingly to the audio input, and the FM wave is spread by the external antenna. By using a standard TV antenna, the range of this transmitter can go up to 1KM radius, using small (15-20cm) Ariel, it can work up to around 50M range. This circuit is most suitable for miniature FM transmitter for use in computer, mobile etc to send music to home theater system without wires, and in homemade wireless walky-talkies.
For input from low power output devices, such as mobile, computer’s sound card, the value of the unlabeled capacitor is 0.1 or 104. For higher wattage outputs, the value is 0.01 or 103. An optional microphone pre-amp can be also added in this circuit to enable it transmit voice directly.
Keep in mind that this type of RF projects are allowed for personal use.
Parts list:
Transistor BF494
Resistor of various value(all 1/4 watt) x4
Capacitor of various value(all 10V, small, ceramic) x3
36 SWG copper wire for coil 1 inch
Input audio jack
Ariel(stick antenna)
Battery CR2025
Related Links
Downloads
The Simplest FM Transmitter Ever Made - Link
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