AVR-based FM-transmitter

This is a very cute hack that does something which I thought was impossible: an implementation of an FM transmitter that has exactly two components: a battery and an ATtiny45 microcontroller. It’s brilliantly obtuse and cool:

Sprites mods – AVR-based FM-transmitter – Intro, theory

The basic idea is to trick the internal oscillator of the Atmel to run at 24Mhz. An internal PLL will run at 4x that frequency, which is a 96 Mhz signal (right in the middle of the FM broadcast band). By varying the frequency up and down, you can generate an FM modulated signal. Beyond clever. Very cool.

1 thought on “AVR-based FM-transmitter”

  1. The only problem is that it’s very inefficient. It’s generating square waves, which contain plenty of harmonics (noise). Sprite’s post got me into playing with a PIC12F1840, which has an on-board mixer, and then running the output through a filter…it’s interesting, but I’m broadcasting at 8MHz.

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