DSP PLL Stereo FM Transmitter Module w/ LCD Display 87-108MHz

The module operates from a 3 to 5 VDC power source, typically drawing under 50 mA at minimum volume and up to 400 mA at maximum output. Ensure your power supply can provide stable voltage within this range to prevent audio distortion or frequency instability. A regulated 5V USB power bank or bench supply is recommended for optimal performance and clean RF output.

You can set the frequency via the onboard buttons and LCD menu or program it remotely using serial AT commands sent to the module's UART interface. The PLL synthesizer allows precise tuning from 76.0 MHz to 108.0 MHz in 0.1 MHz steps. The LCD displays the current frequency, volume level, and operating mode. Refer to the command set documentation for baud rate settings (typically 9600 bps) and specific AT instructions for frequency changes and squelch configuration.

The module supports stereo audio input via a 3.5mm headphone jack for line-level signals and includes a built-in microphone preamp. It automatically switches between mono speaker and stereo headphone outputs. The headphone output delivers up to 500 mW, while the amplified speaker output can drive up to 3 W into an external speaker. Ensure your audio source matches the expected input level to avoid clipping or over-modulation of the FM carrier signal.

The integrated DSP implements a programmable digital squelch that mutes the audio output when the input signal falls below a user-defined threshold, eliminating background hiss. This function must be enabled via the module's settings menu or AT command. Combined with the phase-locked loop and quartz crystal stabilization, it ensures a clean, drift-free broadcast without the traditional FM rustle, making it suitable for continuous transmission applications.