FM Stereo Transmitter circuit diagram Using BH1417

This circuit diagram is part of an RF circuit. It features an FM transmitter circuit diagram using the BH1417 integrated circuit from RHOM, which incorporates multiple functionalities in a compact design. The IC includes pre-emphasis and a limiter to maintain consistent audio levels during transmission, a stereo encoder for stereo output, a low-pass filter that attenuates audio signals above 15 kHz to mitigate RF interference, and a phase-locked loop (PLL) circuit that ensures stable frequency transmission without drift. Additionally, the circuit contains an FM oscillator and an RF output buffer. The schematic allows for 14 selectable transmission frequencies, spaced 200 kHz apart, which can be chosen using a 4-DIP switch. The frequency range spans from 88.7 to 89.9 MHz and from 107.7 to 108.9 MHz. The BH1417 operates with a supply voltage of 4 to 6 volts and consumes approximately 30 mA, delivering an RF power output of 20 mW. The IC achieves a channel separation of 40 dB, which is satisfactory, although the older BA1404 FM transmitter chip offers slightly better performance at 45 dB channel separation.

The FM transmitter circuit utilizing the BH1417 is designed for efficient and reliable audio transmission in the FM broadcast band. The integrated circuit BH1417 serves as the heart of the transmitter, providing a range of essential features that facilitate high-quality audio broadcasting. The pre-emphasis circuit enhances higher frequency audio signals, ensuring that the transmitted sound is clearer and more dynamic. The limiter function is crucial for preventing distortion during transmission, particularly when dealing with varying audio levels, thus maintaining a consistent output.

The stereo encoder allows the circuit to transmit stereo audio signals, enhancing the listening experience for users. The low-pass filter is an essential component that helps to eliminate unwanted high-frequency noise, which can cause interference with the RF signal. This feature is particularly important in maintaining the integrity of the transmission, especially in environments with multiple radio frequency sources.

The PLL circuit is a sophisticated feature that locks the transmission frequency to a stable value, preventing drift that can occur due to temperature changes or component variations. This stability is critical for ensuring that the signal remains on the intended frequency, thereby minimizing interference with other broadcasts.

The FM oscillator and RF output buffer work together to generate and amplify the RF signal, ensuring that it is strong enough for transmission over the desired range. The inclusion of a 4-DIP switch allows users to easily select from 14 different transmission frequencies, enhancing the flexibility of the device. This feature is particularly useful in urban areas where multiple FM stations may be operating simultaneously, allowing the user to find an unused frequency.

The power requirements of the BH1417 are modest, with a voltage range of 4 to 6 volts and a low current consumption of around 30 mA. This makes the circuit suitable for battery-operated applications, providing a practical solution for portable FM transmission needs. The RF power output of 20 mW is adequate for short-range broadcasting, making it ideal for personal use or small events.

Overall, the BH1417 FM transmitter circuit is a versatile and efficient solution for audio transmission, combining multiple functionalities in a compact package while ensuring high-quality performance and ease of use.This circuit is a circuit diagram is included in the RF circuit. FM Transmitter circuit diagram using the IC BH1417. Where the integrated circuit design from RHOM which includes many features in one small package. He came with pre-emphasis, limiter so that music can be transmitted in the same audio level, stereo encoder for stereo transmission, lo w pass filter that blocks audio signals above 15KHz to prevent RF interference, PLL circuit that provides a solid frequency transmission (no more frequency drift), FM oscillator and RF output buffer. The following is a schematic drawing: There are 14 possible transmission frequencies with 200KHz adding that the user can choose a 4-DIP switch.

Band lower frequency ranging from 88. 7 to 89. 9 MHz, and the frequency band from 107. 7 to 108. 9 MHz. BH1417 can be given with 4-6 voltage and consumes only around 30mA, provides RF power output of 20mW. BH1417 provides 40db channel separation is quite good, although older BA1404 FM Transmitter chip provides 45dB channel separation a little better.

🔗 External reference