[mlyle]

The thing is, ... anyone who's playing with microcontrollers and longish wires is making similar RF noise.

Efficiency of, and coupling to, this antenna is going to be garbage, even for harmonics. And the breadboard itself provides a fair bit of attenuation of the already-small 10MHz-and-up content.

> the maximum output current is 40mA and maximum output voltage is 5.5v

Looking at the maximum power you're supposed to draw from a pin isn't useful. The output transistors can provide much more: it's just not good for the part.

It'd be better to consider the radiation resistance of the wire and the AC voltage driving it.