Radioactive Rain Vs. Ludlum Scintillation Counter

I match my new Ludlum model 12 with a Ludlum 44-2 1" NaI(Tl) scintillation detector against some rain water which feel on my car. :) Note: I have stopped using Cyberlink Power Director 10 (video editing software) because it was so unstable and buggy. Note: That water sample, on second glance, might have had a tiny "bump" near the 662 keV photo peak for Cs137. I might need to retest it with my new software (I wrote) to account for my detector's falling efficiency with respect to channel.