After over 27 years of faithful service, the original 101.5 FM transmitter has been retired and replaced with a 21st century upgrade. The new version eliminated an audio chain on 3 circuit boards (pre-emphasis, 19kHz notch filter, and stereo generator), and traded a drift-prone, free-standing oscillator with a digitally synthesized one. | I based it on the Si4713 chip from Silicon Labs and the Adafruit breakout board paired with an Arduino Uno microprocessor. It is even capable of displaying text on modern receivers, just not as sophisticated as song information (yet). I then coupled it with a 3-transistor amplifier I built for a modest increase in power over the original. | I have since updated the technical section with photos and schematics of the new gear, along with helpful programming tips for better performance on the digital side, including a bonus tutorial on how to run Radio Text+. Hey, I may be getting old, but my underground FM stereo radio hobby will always make me feel like a kid again!
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