> From: Peter Chadwick <Peter.Chadwick@gpsemi.com>
> To: amps <amps@contesting.com>
> Subject: [AMPS] failure
To: <amps@contesting.com>
> Date: Wed, 18 Jun 97 15:25:00 +0000
> Something at the back of my mind says that I've seen somewhere that one
> shouldn't run a thoriated filament in saturation, but I can't remember
> why - the penalty of getting old, I guess. If you run it too hot, then
> you boil out the thoria, but doesn't something nasty happen if you run
> it too cold, besides not getting enough emission?
Hi Peter,
Everything I've read indicates no damage occurs to a thoriated tungsten
emitter from attempts to run excessive current. The emission
simply stops increasing.
For the thoriated tungsten example, Eimac's Care and Feeding gives
specific peak emission is between 70 and 100 mA per watt of filament
heating power. Reference Data for Radio Engineers lists emission as
115 mA maximum per watt in larger filaments, and Electronic Designers
Handbook lists a range of 50-100 mA.
All three books indicate thoriated tungsten filaments are not
damaged, or permanently damaged, by emission saturation.
When three reliable independent sources agree so closely, I get a
good feeling about the data.
73, Tom W8JI
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