biemsterThis will be a short log, rain water apparently is not significantly active (despite other claims). The increase in CPM is about 10-20%, not even close to the 10x as claimed in the first link.
This might be due to my location close to sea. This natural background comes from radon outgassing from the earth's crust, which might be filtered out by seawater as it bubbles up there. This way the air above sea is much less active as above land, and when the wind comes from the direction of the sea, this inactive air stretches over land a bit. This is just a loose theory of mine though, please comment below if I'm wrong.
Short story even shorter, calibrating using rain water as a source is not an option for me.
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Have your tried using potassium salt? It's also known as low sodium salt. I used it to test my geiger counter at home a few years ago (check it here: http://tinkerman.cat/geiger-counter). I measured a 5x increase over background.
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I didn't yet. I seem to remember that for the salt you need a pancake tube to be able to detect a significant increase, I only have two STS-5's. What tube does your counter have (link doesn't work)?
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Oh, link does work for me... :(
Anyway, I used a SBM-20 which is kind of a less-old STS-5. Very similar in properties. I bought the PCB with the HV circuitry (way more complex that yours, I like yours better) and implemented the counter with an ATMega328 and an XBee reporting to a gateway. My background count is in the 20-40. It goes up to about 130 when in presence of a small back of potassium salt.
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Link works now, my provider had some connection issues, that was probably the culprit. Nice kit you built :). I'll for sure go find some potassium salt, considering you get such nice results! Thanks!
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