[Milsurplus] Mil Surp and radiation

[Neil Barnett]

I have heard that early VR tubes had something in them to keep the 
ionization up in the gas so they would start easier. Anyone have a list of 
what ones these would be? I have a box of them and am now dubious. Should I 
buy a "dentists x-ray bib"?

Jim Falls
KG6FWT
Eureka, CA


Jim,
Ionization doesn't begin until the voltage across the VR tube is high
enough to cause current to flow through it.  Maybe you're confused
about the "trigger", an electrode like a grid fitted to some VR tubes.

Normally, VR tubes require a starting voltage somewhat higher than
their nominal rated voltage.  The trigger, fitted close to the cathode
and fed from the B+ line through a high value resistor, was designed
to ensure reliable starting (ionization) at a lower voltage than would
be normal for the tube.

73 de Neil ZL1ANM