Quality FM transmitter circuit

This house FM transmitter for your stereo or any other amplifier provides good signal strength up to a distance of 500 meters with a power output of approximately 200 mW. It operates on a 9V battery. The audio-frequency modulation stage is constructed around the BF494 transistor (T1), which is configured as a VHF oscillator and modulates the audio signal present at the base.

The FM transmitter circuit primarily consists of a BF494 transistor functioning as a VHF oscillator. The oscillator's frequency can be adjusted by varying the values of the external components, such as capacitors and inductors connected to the transistor. The audio signal is fed into the base of the transistor, where it modulates the frequency of the carrier wave generated by the oscillator.

The power output of 200 mW is sufficient for broadcasting over a distance of 500 meters, making this circuit suitable for personal use in home audio systems. The 9V battery supply ensures portability and ease of use, allowing the transmitter to be utilized in various settings without the need for external power sources.

To enhance the performance of the transmitter, it is advisable to incorporate a proper antenna design. A quarter-wave monopole antenna can be used, which is typically about 0.75 meters in length for the FM band. The placement of the antenna should be elevated and away from obstructions to maximize the range and quality of the transmitted signal.

Additionally, careful consideration should be given to the modulation depth and audio signal quality to ensure clear transmission. This can be achieved by using high-quality audio sources and maintaining appropriate levels to avoid distortion. Implementing a low-pass filter at the output stage may also help in reducing unwanted harmonics and improving overall signal clarity.

In summary, this FM transmitter circuit is a compact and effective solution for personal audio broadcasting, capable of delivering a strong signal within a considerable range while being powered by a standard 9V battery. Proper component selection and circuit design will contribute significantly to the overall performance and reliability of the transmitter.This house FM transmitter for your stereo or any other amplifier provides a good signal strength up to a distance of 500 meters with a power output of about 200 mW. It works off a 9V battery. The audio-frequency modulation stage is built around transistor BF494 (T1), which is wired as a VHF oscillator and modulates the audio signal present at the base.

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