Item specifics
Description
FM Radio Transmitter Module Product Overview
The FM Radio Transmitter Module is a stereo FM transmitter based on the KT0803 series chip. It converts audio from the onboard microphone or audio input into an FM radio signal in the 70-108MHz band, which can be picked up by any standard FM receiver. The module features an I2C interface (5V TTL compatible), a wide input voltage range of 3.0V-5.0V, an onboard microphone, and is designed for plug‑and‑play use. It's ideal for DIY mini radio stations, wireless microphones, car audio transmitters, and other projects, making it simple to share music and voice.
FM Radio Transmitter Module Core Features
The module is built around a high‑performance KT0803K/L stereo FM transmitter chip, integrating a 20‑bit delta‑sigma audio ADC and a DSP core. With features like automatic level control and silence detection, it achieves a signal‑to‑noise ratio of 66dB and stereo separation over 40dB for professional‑grade audio transmission.
The transmitter covers the global FM band from 70MHz to 108MHz. Frequency can be set in 0.1MHz steps via the I2C interface. An onboard 32.768KHz crystal provides accurate and stable frequency generation.
Power consumption is extremely low: only 17mA during active operation and just 3µA in standby, making it ideal for battery‑powered portable applications. The supply voltage ranges from 3.0V to 5.0V, allowing it to be powered directly from an Arduino's 3.3V or 5V pin, seamlessly compatible with various development boards.
The module features a high‑sensitivity onboard microphone and a mono audio input jack with built‑in preamp, eliminating the need for external components to pick up sound. It can also be connected to external sources like phones or computers via an audio cable. Output power can drive earphones or small speakers; transmission range depends on antenna length and environment (using a 75cm antenna, it can propagate several tens of meters in open space). The RF output pad is provided for antenna connection; a 75cm piece of ordinary wire is recommended for best performance.
The module uses an I2C interface (SDA/SCL) compatible with 5V TTL levels, making it easy to communicate with mainstream microcontrollers like Arduino and Raspberry Pi. You can programmatically adjust frequency, volume, and input gain, catering to DIY enthusiasts, educators, and developers. Its compact size (approx. 37.7×26.4mm) makes it easy to embed into portable devices, allowing you to create your own personal FM radio station anytime, anywhere.
FM Radio Transmitter Module Applications
DIY Mini FM Radio Station: Build a mini FM station with an Arduino to broadcast music or voice to multiple FM receivers simultaneously – perfect for campus radio, community sharing, or small events.
Wireless Audio Transmitter: Wirelessly transmit audio from a phone, MP3 player, or computer to a car radio, eliminating AUX cables and enjoying music on the go.
Wireless Microphone System: Create a wireless microphone using the onboard mic for presentations, classroom amplification, KTV, or stage performances, with reception on any FM radio.
Robot / Smart Car Voice Broadcast: Add voice broadcast capabilities to a robot or smart car for real‑time status updates, navigation, or voice alerts.
Audio Source Testing / Teaching Experiments: Use as an FM source for testing radio sensitivity or building electronic course projects, offering a clear demonstration of wireless transmission.
FM Radio Transmitter Module Key Advantages
The module integrates a highly integrated KT0803 chip, combining audio ADC, DSP, and RF transmitter into a single IC with minimal external components – drastically lowering the barrier for DIY mini FM radio stations. Unlike discrete FM transmitter kits, it delivers stable, drift‑free performance without tedious tuning.
I2C digital frequency adjustment eliminates the inaccuracy and instability of analog potentiometers. With a few lines of code, you can precisely set the frequency in 0.1MHz steps, as well as read chip status and adjust volume and gain – making it ideal for human‑computer interaction and automated control.
Highly integrated, the module includes an onboard microphone and audio input, eliminating the need for external audio processing circuits. With onboard LDO and crystal, only power and I2C connections are needed – truly plug‑and‑play.
Ultra‑low power consumption (17mA active, 3µA standby) makes it perfect for battery‑powered portable wireless microphones or speakers, providing long operating hours on a single charge.
The module is available with or without soldered pins, allowing flexible integration with pin headers or direct soldering. With ready‑to‑use libraries for platforms like Arduino, just a few lines of code are needed to control the transmitter – making it a go‑to tool for maker projects, wireless audio retransmission, and educational demonstrations.
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FAQ:
What is the I²C FM radio transmitter module and what are its key features?
This is a compact stereo FM transmitter that broadcasts audio over a selectable frequency between 70 MHz and 108 MHz. It is controlled entirely via I²C, making it perfect for Arduino, ESP32, and Raspberry Pi projects. Key features include an on‑board MEMS microphone, a 3.5 mm line‑in jack, a built‑in antenna, and plug‑and‑play compatibility with standard I²C libraries. No manual tuning is required—just set the frequency in your code and it starts transmitting.
How do I connect the FM transmitter module to an Arduino? What pins are used?
Connect the module's VCC to 5 V (or 3.3 V if the module is 3.3 V‑only—check your board silkscreen). Connect GND to GND, SDA to A4 (or the dedicated SDA pin on newer Arduinos), and SCL to A5 (or the dedicated SCL pin). Most modules include a voltage regulator, so they can be powered directly from the Arduino's 5 V pin. For microcontrollers with 3.3 V logic, use a 3.3 V supply to avoid damage.
Is there an Arduino library for this FM transmitter module? How do I set the frequency?
Yes. For modules based on the KT0803L or QN8027 chips, libraries such as “KT0803L” or “FM‑Transmitter” are available in the Arduino Library Manager. After installing, you call a simple function like `fm.setFreq(101.7);` to set the frequency in 0.1 MHz steps anywhere from 70.0 MHz to 108.0 MHz. The library handles all I²C communication and chip initialisation.
Can this module transmit stereo audio? How do I enable stereo mode?
Yes, it supports true stereo transmission. In most libraries, stereo is enabled by default. If you need to switch it, a single register write (e.g., `fm.setStereo(true);`) configures the internal DSP to send the left and right channels separately. The FM receiver on the other end will automatically detect the pilot tone and switch to stereo.
How do I switch between the built‑in microphone and the line‑in jack?
Many modules have a tiny solder‑jumper or a software‑selectable register. By default, they often give priority to the line‑in jack: when a 3.5 mm plug is inserted, the microphone is automatically muted. If your module allows software control, you can force the microphone input via an I²C command. Check the specific library documentation for the chip used on your board.
How can I improve the audio quality and reduce background noise?
Use a clean, well‑filtered 5 V power supply—noise on the supply rail directly modulates the carrier. Keep the audio input wires short and shielded. The on‑board antenna should be fully extended; for longer range, solder a 75 cm piece of wire (quarter‑wave at 100 MHz) to the antenna pad. Some modules also benefit from a small pre‑emphasis capacitor setting, which can be adjusted via the library.
What is the typical transmission range of this FM module?
With the built‑in antenna, you can expect a reliable range of 10–30 meters in open air. Inside a building, walls and metal objects reduce the range to about 5–15 meters. Adding a proper quarter‑wave antenna and using a clean power source can extend the range to 50 meters or more. The actual range also depends on the receiver sensitivity.
Is it legal to use this FM transmitter module? What power does it output?
These modules typically output less than 10 mW, which falls under most countries' low‑power device regulations and may not require a license for personal use. However, regulations vary by region. Always check your local radio‑frequency laws before broadcasting. For hobbyist use indoors or in a car, the range and power are generally acceptable, but public broadcasting may require a license.
Why can't I hear any sound after setting the frequency? How do I troubleshoot?
First, make sure your radio is tuned exactly to the frequency you set in code. Check that the module is receiving audio: if using line‑in, verify the source is playing; if using the on‑board mic, tap it and watch for any LED flicker (if present). The I²C address may be incorrect—try scanning the bus to confirm the module is detected. Finally, ensure the antenna is connected, as some modules will not transmit without one.
What are the most common Arduino and DIY projects that use this FM transmitter?
It is used to build homemade car MP3 players, wireless audio for holiday light shows, synchronized music broadcasting in escape rooms, DIY baby monitors, and simple wireless PA systems. Its I²C interface makes it easy to integrate with Arduino‑based home automation, where you can transmit voice alerts or streaming audio over FM.