Geiger Counter + Gamma spectrum analyzer under 10€

This does seem to promise easier/cheaper Gamma detection than a smart phone. The larger area and known characteristics/shelding should make it more useful for higher energy detection. GM tubes must be more sensitive due to the high voltage avalanche feature.

My software currently has no compensation for the photodiode characteristic. I'd like to include it, however I was not able to google out something definitive.
However the data gathered are stored in easy readable numbers that can be processed any way.

Despite the cons about it, it is a interesting project. I have seen some pin diode units on ebay.

In fact, I just noticed that Radlog station Vinkx in Kapellen, Belgium is using a Rasp.Pi 2 with two X100-7 PIN diode sensor boards.

Sure, but those diodes are expensive, one costs around 100$.
And they are designed to be gamma detectors.
The diodes in the circuit I had posted can be changed for anything you like and I am sure it can be improved with some more expensive and and more sensitive photo diode.

I found this on DExUS' website, then found it here. Thank you DExUS.
Built the circuit a few days ago and tested today. Seems to be doing some kind of signal level recording. I know little about this! I assume the numbers given for Channels are just that, channels showing the audio level of each hit, not actual keV. The numbers change when different Channel is selected (512, 1024). Not sure DExUS visits this website since the last log in was years ago, anyone have some guidance as to what I am seeing? The images are data from a thorium lantern mantle recorded 4 hours, 27 minutes. Also potassium Chloride recorded for 13 hours.
Perhaps I need to test a few items that I can find spectrum graphs for, then compare to my graph so I can guess keV numbers.