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Stereo Digital FM Transmitter Circuit


Advanced Member level 4
Sep 26, 2007
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Without a doubt, FM transmitter and Receiver are among the top favorite electronic project topics, however, building a digital FM transmitter can be a challenging project for electronics enthusiasts. The transmitter can then be connected to a source of audio, such as a phone or computer, to broadcast music or other audio content.

In this project, I have introduced a compact stereo digital FM transmitter circuit that operates in the frequency range of 87MHz to 108MHz. The frequency can be adjusted using two tactile push-buttons, with a 0.1MHz step size. The heart of the circuit is an ATMega8 microcontroller, which communicates with a 0.96-inch SPI OLED display and the KT0803L FM transmitter chip via an I2C interface. You can directly connect a microphone or an AUX cable to the board to broadcast your desired sound, such as playing a piece of music from your cellphone, computer, … etc. After conducting some tests, it was found that the circuit operates quite stable, and the received sound is clear and sharp.

To design the schematic and PCB, I used Altium Designer 23 and shared the project with my friends to get their feedback and updates using Altium-365. The fast component search engine (Octopart) allowed me to quickly consider components’ information and also generate the BOM. To get high-quality fabricated boards, I sent the Gerber files to PCBWay. I am confident that utilizing this circuit will be an enjoyable and fulfilling experience for you.



Full Article + Schematic + PCB + Code:

[1]: TLV1117-5.0:

[2]: TLV1117-3.3:

[3]: MMBT304:

[4]: 2N7002:

[5]: KT0803L:

[6]: ATmega8-AU:
If you design a Power Amplifier and a Harmonic Filter just beyond the circuit, it might be used for amateur broadcasting purposes. If you need a RF design support, I can help you.

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