Fm Stereo Transmitter Circuit

A BA1404 integrated circuit (IC) is utilized to generate a complete FM multiplex (MPX) signal. The chip incorporates all necessary circuitry. Components CI, R3, R4, and C4 are responsible for providing pre-emphasis. The transmitter operates on a single AA cell. L3 consists of three turns of #20 wire wound on a Ke drill for form. L3 is of considerable length. L4 is composed of four turns of #20 wire wound on a Me drill bit, with specific spacing. For monophonic operation, it is advised to omit C5 and the components associated with the 38-kHz oscillator.

The BA1404 IC is designed for FM stereo broadcasting and is capable of generating a high-quality multiplexed audio signal. The pre-emphasis circuit, formed by the components CI, R3, R4, and C4, enhances the higher frequencies of the audio signal before transmission, which is crucial for improving the signal-to-noise ratio and ensuring better reception quality.

The transmitter's power supply is a single AA cell, providing a compact and portable solution for FM transmission. The use of L3 and L4 as the inductors in the circuit is critical for the tuning and stability of the oscillator. L3, with its three turns of #20 wire, is designed to provide a specific inductance value that is necessary for the desired operating frequency. The length of L3 is important as it can influence the inductance and thus the performance of the oscillator circuit.

L4, consisting of four turns of #20 wire, is similarly designed to contribute to the circuit's tuning characteristics. The specific spacing on the Me drill bit is essential to achieve the required inductance and to minimize unwanted capacitance that can affect the circuit's performance.

For applications requiring monophonic audio transmission, the design can be simplified by omitting C5 and the components associated with the 38-kHz oscillator. This modification allows the circuit to operate in a simpler mode, which is beneficial in scenarios where stereo sound is not necessary, thus reducing component count and complexity while maintaining functionality.

Overall, this circuit design utilizing the BA1404 IC is suitable for various FM transmission applications, offering flexibility in operation modes and ease of implementation. A BA1404 IC is used to generate a complete FM MPX signal. The chip contains all of the necessary circuitry. CI and R3, and R4 and C4 provide pre-emphasis. The transmitter runs on a single AA cell. L3 is 3 turns of #20 wire on a Ke drill (for a form). L3 is long. L4 is 4 turns #20 wire on `Me drill bit, spaced to %. If monophonic operation is wanted, omit C5 and the 38-kHz oscillator components. 🔗 External reference