N Cook said:
What was the small hinged halved chamber , he used a few times? - for
annealing the glass ?
I did not follow the getter process.
Would someone have to be licensed to get hold of barium, caesium ?
I took that to be an annealing chamber. As far as the 'gettering' process
went, as far as I could see, he used induction heating to bring the anode up
to white heat, whilst running the vacuum pump to evacuate the envelope. I
would guess that this 'burns off' any remaining molecules of gas, or
possibly chemically traps them in the surface of the anode, but will not
leave a chemically active gettering 'splash' on the inside of the glass as
you would normally see, so I suppose over a period of years, the valve will
very slowly become soft, but maybe not enough to severely affect its
characteristics. I know that such chemicals as barium and strontium in oxide
form, are used to coat the cathodes of indirectly heated valves to enhance
electron emission, but I thought that the contents of a 'traditional'
gettering ring, were little more than magnesium ?
I wonder how much current the filament was drawing, to get it up to the
point of sufficient emission ? Certainly, the valves lit up like torch
bulbs, when in use. Did you notice the pair of fans on the QRP transmitter ?
The spot welding machine was interesting too. Looked as though it may have
started life as a small flypress.
Arfa
