I was attracted to the idea of having a wireless hum/temp sensor and so I built this. I prototyped it on a breadboard, and I also soldered it on a PCB. I extended the antenna with a 8.3 cm wire.

But I can't get it to work stable. Sometimes it works for many hours and sometimes only for one hour. And then it just hangs. A reset of the at85 sometimes helps, but most of the times I need to power it off and on again.

I need it to work reliably for several weeks. Any suggestions ?