[ARC5] Strange problem with racked transmitters

[Kenneth G. Gordon]

On 28 Jun 2015 at 16:17, Dennis DuVall wrote:

> The blue glow you are  seeing is probably due to electron bombardment of the
> glass tube envelope(s), not gas, and is harmless.

The difference between the two types of "blue glow" is quite obvious once 
you have experienced both: generally, if the blue glow is INSIDE the tube, 
between the plate element and the filament, then it is gas.

If the blue glow is OUTSIDE the plate, and near or up against the glass, it is 
what Dennis described, and this usually indicates an unusually good tube 
with a very hard vacuum.

Ken W7EKB