Created: Aug 29, 2014
No description available.
This simple circuit is a basic application of FM transmission. It is comprised of discrete components with an operation that is quite simple compared to a highly sophisticated wireless transmission. It receives an audio signal from an audio source. The audio signal will be mixed with the FM frequency range signal and its output signal is transmitted to a a tuned FM receiver.
The circuit is supplied by a 9V battery and the 0.047uF capacitor is used for the stability. The circuit is supplied to the resistor 27kΩ positive in the leg microphone,and it is way out of with the audio signal,through the coupling capacitor to pin B of the transistor. The 2N2222 transistor act as both the radio frequency generator and the audio mixer on the radio frequency generated. The resistor 27kΩ and 4.7kΩ are divider circuit to bias the transistor. The coil uses a copper wire No. 19-20 AWG, wrapped around the air core diameter of 7 mm. The 5pF to 20pF trimmer capacitor is used as the tuner. The pin C of the transistor is connected to the antenna with the coil with wire No. 16-20 AWG, 7 inches in length, curled into a circle like a spring about 6 mm in diameter.
The circuit is applicable to short distance wireless communication and also in broadcast communication.