Thanks for the reply. I guess I'm looking for some general guidlines here. Did you choose the bird feeder because it's not completely sealed? Is air flow around the unit important? At first glance, I would say I could just get a plastic electrical enclosure, like a pvc junction box. But maybe it needs air flow, or maybe it's important to minimize the thickness of the enclosure walls.

I watched the Mr. Wizard video and it seems to me that we're just not going to be reading much in the way of alpha particles. And Gamma doesn't get knocked out by much of anything, so you could basically keep the unit inside for that. So it boils down to Beta, right? It looks like for Beta you want to put as little material around the unit as possible. They didn't show the difference when plastic is placed between the radiation source and the Geiger counter.

You mention the location of the Geiger tube. Is it directional? Does the radiation have to come from one direction, or along a particular axis?

Is there some article on this subject I missed? I would be happy to read up on it rather than drive you nuts with questions. I just want to try and set this up right and not have the little woman after me about the rats nest of wires and do-dads hanging off the side of the house.