FM Beacon Broadcast Transmitter (88-108 MHz) circuit
The circuit operates by utilizing a 555 timer configured in astable mode to generate a square wave signal at a frequency of around 600 Hz. This square wave output is then used to modulate the frequency of a Hartley oscillator, which is designed to operate within the FM broadcast band. The Hartley oscillator consists of an inductor and two capacitors, which determine its resonant frequency. By applying the square wave from the 555 timer to the oscillator, the output frequency of the Hartley oscillator is varied, producing frequency modulation.
The power supply for this circuit is a battery that can provide a voltage between 6 to 9 volts. The circuit is designed to draw a current of approximately 30 mA, ensuring it remains efficient for battery operation. The effective transmission range of about 100 yards makes this circuit suitable for various applications, including remote control systems and security alarms.
To enhance the performance of the circuit, proper tuning of the Hartley oscillator is essential. This can be achieved by adjusting the values of the inductor and capacitors used in the oscillator circuit. Additionally, incorporating a suitable antenna can significantly improve the transmission range and clarity of the audio tone being broadcasted. A simple dipole antenna or a quarter-wave monopole antenna can be used, depending on the desired range and application requirements.
Overall, this circuit provides a straightforward solution for transmitting audio signals over FM frequencies, making it a versatile option for hobbyists and professionals in the field of electronics.This circuit will transmit a continuous audio tone on the FM broadcast band (88-108 MHz) which could used for remote control or security purposes. Circuit draws about 30 mA from a 6-9 volt battery and can be received to about 100 yards. A 555 timer is used to produce the tone (about 600 Hz) which frequency modulates a Hartley oscillator..
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