FM Tracking Transmitter Using a 555 Timer

Circuit diagram is designed for tracking transmitter audio tone in FM frequency band. Circuits that can be used the signal transmitter or remote control transmitter. In circuits that use only components that are available. Transmitter’s range is 100 m in the distance using the 9V power supply and matching the antenna. 

Circuit diagram is built by IC timer 555 to produce audio and tone based on the JFET in the circuit as the core. JFET circuit operation is the first (Q1) is the cable as a Hartley oscillator frequency modulated by the audio tone. The second (Q2) JFET is wired as a buffer to isolate the oscillator from the antenna based on the Q1. Diode D1 is used as varactor here.

The diode is reverse bias voltage generated by slim on pin 2 & 6 of IC1 results. This change in capacitance of the junction diode reverse bias, which in turn change the frequency of the oscillator to achieve frequency modulation.   For inductor L1 can be made by winding 5 turns of 18 SWG enameled copper wire on 3 / 8 inches long, 3 / 16 inch diameter plastic tube. The coil must be tapped in the center. The antenna can be a 20cm long wire.

http://freecircuitdiagram.net/fm-tracking-transmitter-using-a-555-timer.html