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[email protected] pfjw@aol.com is offline
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On Wednesday, April 25, 2018 at 7:40:06 AM UTC-4, wrote:
On Wednesday, April 25, 2018 at 6:02:47 AM UTC-4, wrote:

before dull valve emitters were discovered, valves/tubes used thoriated tungsten direct heated bright emitters. They ran white hot. Nuke magnetrons use thoriated tungsten bright emitters.


These must go back to pre-DeForest days??

I have some direct-heat thorated tungsten 00, 01 and 71A tubes, as well as a number of UV99s and similar. Not a one of them gets much past a mild orange.
Not to mention 2A3, 10 and 50s. The closest thing to a "hot" tube I have is a 10, and that filament is about like a 25 watt tube running at 50V or so.

Which tubes are these?


On further research:

The cathode of a magnetron provides the electrons through which the mechanism of energy transfer is accomplished. The cathode is located in the center of the anode and is made up of a hollow cylinder of emissive material (mostly Barium Oxide) surrounding a heater. The feeding wires of the filament must center the whole cathode. Any eccentricity between anode and cathode can cause serious internal arcing or malfunction.

Does not seem to be much Thorium involved??


Peter Wieck
Melrose Park, PA