GM Tubes - Sov Tube Purchase

Hi All. Just received three GM tubes from Sovtube. A standard SBM-20, a CI-22BG, and a SBT-11A. Though the SBT-11A is interesting, and the most expensive at $30.00, the best buy was the large CI-22BG.

This is the size of an 8 inch long fluorescent light. At 400 VDC, it is showing 65 CPM cosmic ray background. At $10.00, it is a bargain. I'm guessing it isn't popular because of the large size, but it is "bang for the buck".

I'm going to see about ordering more, setting up two in a co-incidence detector for cosmic rays.

I've tested the tubes on a GK4 DIY kit by Brohogan, and with my own variable HV supply.I've used Aware's AW-RADW on a serial port (pins 5 and 9 ring with no capacitor) and with Geiger Graph, (pin 5 and pin 2, RX, through a capacitor).
Count results are consistent, around 65 cpm. That's twice what I'm getting with my LND7313 1.75" pancake detector.

The SBT-11A is neat. I'm putting it in a small ABS plastic box as a probe with a female connector to mate with my GK+4 kit from Atomic Dave. (also a Brohogan PCB). A ham radio buddy is cutting the rectangular hole for me. Atomic Dave provided some stainless steel mesh. The three anode pins at one end will be common, joined to a 10 megohm resistor. The two ground pins opposite (in the middle) are made common. This 4 segment tube is very sensitive to alpha.

If anybody wants pictures, just drop me an e-mail.
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Though I'm blind, taking pictures with a Canon digital is a lark.

The SBT-11A is a cracker! Best value alpha detection for the money....if you get a good one. Ive bought six, 3 were duds. First a good one, Then two duds came from sovtube before I shopped elsewhere.
Better alpha detection than the LND-7317 but not as good an all-rounder.
I connect the three + pins with three separate 4.7M ohm resistors and run it at 390V.

I've never tested a CI-22BG. Looks neat. Is it affected by bright light?

Regarding the CI-22BG (SI-22BG), we don't have much of the sunlight commodity here today.
So, I unwrapped the polyfoam protection, then flashed the bare tube with UV-C from a toothbrush sterilizer. Lots of ozone from the UV-C, but no change in the sporadic background clicks.

Since I can't see, I can't tell you if the tube is somehow internally coated, like with aquadag.

Just ordered two more. One in case of breakage, the other for a coincidence detection setup. For that, I'll be using a 2 channel divider and stereo inputs to my PC running Marek Dolleiser's PRA (Pulse Recorder & Analyzer) free software (Uiniversity of Sydney, Au.). He very graciously modified his program a few years ago so that it is compatible with my JAWS screen reader.


Last night I also ordered 2 of the SBT-11A's from Sovtube. Sure hope they aren't duds.

When I asked, Atomic Dave told me he just hooked the SBT-11A up by making the two ground pins common and three anode pins common with only one resistor. That works. I'd have to check my mail to see if he mentioned what resistance value. I used the 10 megohm resistor to be on the safe side.

Early on, I was testing anode connections, applying HV to different pins. I did notice sensitivity to an americium alpha button shifted locations.

I'll test the next tubes with variations.

Mind sharing the source for the good tubes?
Three years ago, I purchased two NaI(Tl) scint crystals from Sovtube. 18 X 40 MM and 25 X 75 mm (approx.) and just ordered another 30 X 70 mm crystal. Thus far, everything, including the GM tubes has been A+.

.....oh no! I just spent about an hour writing a researched response to your msg - pressed submit and was promptly told that my session had expired.... arrrr!
I'll try again tomorrow.

"Mind sharing the source for the good tubes?" - no problem, eBay Australia seller any-devices. I've bought a number of SBT-10s and SBM-20s there too. Also, http://shop.boxtec.ch have a quality selection...

Using an individual resistor for each segment in a multi segment gm tube was recommended to me by RH Electronics, the idea being to ensure a balance of current in each segment. Made sense to me.