My station has a new more sensitive Geiger tube SBM-19 :-)

This is a great tube, I have one. I calculated the conversion factor from John's page on different tubes https://sites.google.com/site/diygeigercounter/gm-tubes-supported
I don't remember exactly what it was off the top of my head, I'm back to a SBM-20 for the time being.

What do you mean by 'compatible clicks'? If you mean the conversion factor (cpm to uSv/h) kokohd wrote it in the post above yours - 0.0018 uSv/h for every single click per minute, which sounds about right.

I have a SI22G which is a similar tube in size and sensitivity and the conversion factor for that is 0.001714 (uSv/h to one click/CPM). I have also been collecting conversion factors for any tube as and when I come across them, or if I can work it our from the data sheet.

I have two other conversion factors for the SBM-19 - 0.0015 and 0.0021. The latter is from RH Electronics, the former I have no idea. I assume these are for the different isotopes when Nope, scratch that, AI reckons there is only one sensitivity specified in the datasheet. Some tubes have two, one for beta and one for gamma, however this tube just has the one. And interestingly, AI calculated it at 0.00130–0.00143 μSv/h per CPM​.

If you need the opposite conversion factor - CPM to 1uSv/h (as opposed to uSv/h to CPM) then simply divide 1 by one of the numbers above. So if we use the higher of what AI suggested (0.00143) the we divide 1 by that number (1 / 0.00143) that gives us 699.3. So 699 CPM = 1uSv/h.

Personally, after what AI replied with, I'd be tempted to use the 0.0015 conversion factor (or 666.7 depending which way you use it).

I have attached the datasheet(s) (in Russian) and also the output from AI verbatim below the datasheet(s).

 

 

AI:
The important line is item 6, “Чувствительность S” = Sensitivity.
For the SBM-19 column, the datasheet says:
Sensitivity: 420–460 impulses/s at P = 1.0 μR/s
In other words:
1 μR/s→420–460 CPS
This agrees with another published transcription of the SBM-19 specification.  https://www.istok2.com/data/2397/

Using the midpoint:
S≈440 CPS/(μR/s)
Convert that to CPM:
440×60=26,400 CPM/(μR/s)
And:
1 μR/s=3600 μR/h
So: 26,400 CPM→3600 μR/h
or:
1 CPM→0.13636 μR/h
Converting μR/h to μSv/h

For gamma radiation, the commonly used approximation is:
1 R≈0.01 Sv
so:
1 μR/h≈0.01 μSv/h
Therefore:
1 CPM≈0.00136 μSv/h
​or equivalently:
μSv/h≈CPM×0.00136​

Using CPS instead:
μSv/h≈CPS×0.0818​

Because the specified sensitivity is 420–460 CPS, the datasheet tolerance gives roughly:
0.00130–0.00143 μSv/h per CPM​

So I'd use 0.00136 μSv/h per CPM as the nominal SBM-19 conversion factor derived directly from this particular datasheet.
For example, a reading of 100 CPM would correspond to approximately:
100×0.00136=0.136 μSv/h​

Interestingly, you'll find some hobbyist projects using values around 0.0018–0.0021 μSv/h/CPM for the SBM-19. One DIY Geiger document, for example, gives 0.0021, but explicitly describes its factors as experimental. The discrepancy is worth investigating because the datasheet-derived 0.00136 is substantially different.