Glass Walled Geiger Muller Tube Shootout

This is a comparison of 8 glass walled GM tubes, with a SBM-20 as a control. I did this some months ago, but hadn't pulled all the data together until now.

Of the eight tubes, four are of the J305 flavour - M4011, J305 (2021 - light sensitive), J305 (2023 - not light sensitive) and one that appears to be a copy, with no markings and came in a cheap FS-2011 Geiger counter. The other four are more interesting, or less, depending which way you look at it. The HH614 is from a pen type counter and is quite small and thin. The remaining three are very low sensitivity tubes designed to be used in high radiation areas - SI-3BG, Dextray 3G8B and DOB-50. The J305's and M4011 get easily form AliExpress or your favourite Chinesium outlet. Same for the HH614, but seemingly less available for just the tube on it's own. May be easier to buy a pen type counter, with the tube. SI-3BG - there are usually some of these knocking about on eBay for cheap. The Dextray 3G8B was a one-off eBay purchase. Quite a rare tube, maybe. There is certainly next to no info about it. And finally, the DOB-50 came from a (parts machine) DP-66M.

The tests were performed in a fairly consistent manner on the same counter. Connect the tube and make sure anode resistor and voltage are correct. Shove one source up to the tube, measure over 5 minutes to get an average. Then move on to the next source, and the next and so on. Once the 5 sources and background have been counted, change the tube. Lather, rinse, repeat. The charts are in both linear and logarithmic as the background counts simply weren't showing on the linear chart. Quite surprisingly, the genuine 2019 J305 came out the most sensitive of all, even more than the SBM-20 control, and the Dextray hardly gave any clicks whatsoever, to anything. The SI-3BG (or multiple thereof) would be great for high radiation monitoring, but feels like it doesn't work with not getting a single background count in 5 minutes, but they are cheap, and available. Hmm, after a quick look, they aren't as cheap as when I bought them. They were going for around £5.00 each. I got five for around £16. Now it seems they are around £18 each. I guess that's what war does.

Test results:

Archived from radmon.org - originally posted 06/04/2025