When the Regency TR-1 transistor radio came out onto the market in the 1950s, it was hailed as a modern marvel of microelectronics. With only four transistors and a handful of other components, the TR-1 was a wonder of modern engineering. [Sprite_tm] may have those old-timers beat, though. He built an FM transmitter with the lowest parts count of any transmitter ever.
Like most of [Sprite_tm]‘s builds, it’s an unimaginably clever piece of work. [Sprite] overclocked the internal RC oscillator of an ATtiny45 to 24 MHz. After realizing the PLL running at four times the frequency of the oscillator was right in the middle of the FM band, he set about designing a tiny FM transmitter.
[Sprite_tm] remembered his work on MONOTONE and made a short song for hit ATtiny. The firmware for the build takes the notes from his song and varies the 96 MHz PLL frequency a tiny bit, thereby serving as a tiny FM transmitter.
Does it work? Well, if you want to compare it to a Mister Microphone, the range is incredibly limited. That being said it works. It’s an FM transmitter built out of a microcontroller and a battery, and that’s very impressive. Check out [Sprite_tm]‘s demo after the break.