The SBM-20 is a reliable compact Geiger-Muller tube produced in the USSR in large quantities in decades past. It gives about 10-30 CPM (counts per minute) background radiation in most environments. It replaces for the earlier STS-5 tube, with improved performance and durability.

The tube will come padded but without a box. Each tube is tested and is guaranteed to be fully working. Ships from the east coast US by first class postal service.

Datasheets in English and Russian are readily available online.

Electrical Specifications

• Operating voltage: 350 to 475 V DC
• Minimum anode resistor: 1 MΩ (voltage rating at least 500 V)
• Recommended anode resistor: 5.1 MΩ (voltage rating at least 500 V)
• Plateau length: at least 100 V
• Plateau slope: 0.1% per 1 V
• Minimum dead time: 190 μs (at 400V)

Physical Specifications

• Diameter: 11 mm
• Length: 108 mm (+/- 2.5 mm)
• Weight: 10 g
• Temperature rating: -60 to +70°C