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 GQ Geiger Muller Counter
 GMC300/320 Sensitivity Mod
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honderpilot

2 Posts

Posted - 02/07/2017 :  10:29:09  Show Profile  Reply with Quote
Hey All,

I'm new here and just received my GMC 320. I was measuring some of my uranium glass collection and noticed that my 320 was detecting significantly lower (25%) radiation than a control which was tested with a $300 Soeks Quantum GC. Once I removed the back and exposed the tube then the readings seemed consistent with what I expected. I was thinking about 3-D printing my own back piece for the 320 which covers the board but exposes the Muller tube because I believe that the plastic housing is decreasing the sensitivity. Thoughts?

Thanks!
Reply #1

Distelzombie

Germany
160 Posts

Posted - 02/07/2017 :  11:07:50  Show Profile  Reply with Quote
Hi. Many people did that and its not particularly clear why GQ used such a thick plastic housing with almost no holes. Search this forum a little bit and you'll see many Mods. I for example build in a sbt-11a pancake tube.
You have to recalibrate the device though, whatever you do.

GMC-300E+ V4.20 with sbt-11 alpha tube

My statements are to be taken as stuff-a-hobbyist-says.
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Reply #2

honderpilot

2 Posts

Posted - 02/07/2017 :  18:20:07  Show Profile  Reply with Quote
quote:
Originally posted by Distelzombie

Hi. Many people did that and its not particularly clear why GQ used such a thick plastic housing with almost no holes. Search this forum a little bit and you'll see many Mods. I for example build in a sbt-11a pancake tube.
You have to recalibrate the device though, whatever you do.



Thanks, i'll start looking. If I recalibrate it, would that make it correct or just artificially inflate the readings?

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Reply #3

Distelzombie

Germany
160 Posts

Posted - 02/07/2017 :  18:36:29  Show Profile  Reply with Quote
quote:
Originally posted by honderpilot
Thanks, i'll start looking. If I recalibrate it, would that make it correct or just artificially inflate the readings?



Make it correct? It will change the calculation of ySv/h or the other, more useless thing: mR/h. Nothing else.
Oh, maybe it will change the alarm threshold. Im not sure about this.

Look into the "calibration" thread for how to calibrate correctly. Its sticked to the top of the list.

GMC-300E+ V4.20 with sbt-11 alpha tube

My statements are to be taken as stuff-a-hobbyist-says.

Edited by - Distelzombie on 02/07/2017 18:39:21
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