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Re: Max anode voltage?

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 06:28 PM 5/17/2006, you wrote:
Original poster: "Andrew Bonnell" <andrewbonnell@xxxxxxxxx>

Out of curiosity, how fast to vacuum tubes switch?

leaving aside various and sundry microwave tubes that work by interaction of beams, fields, etc. (Klystrons, TWTs, etc.) and don't really "switch"

You're probably left with things like planar triodes and the like, which probably max out at a GHz or so.

There are some fast switching beam tubes: imagine an electron beam that passes between two plates that bend it left or right, so it hits one plate or the other. The latency through the tube may be significant, but it doesn't take much time to move the beam.


On 5/17/06, Tesla list <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx> wrote:
Original poster: Ed Phillips <<mailto:evp@xxxxxxxxxxx>evp@xxxxxxxxxxx >

Original poster: David Speck <<mailto:Dave@xxxxxxxxxxxxxxxx>Dave@xxxxxxxxxxxxxxxx>


If tubes are anything like light bulbs, you may take a significant
hit on filament longevity by running them at 10% overvoltage.  I read
somewhere that the life of an incandescent lamp varies as the inverse
cube of the current, so that works out to about 75% of the rated lifetime.


With 10% more filament voltage you can probably double the saturation

    I think that the effect of overvoltage on life is even greater
than you state - there's information on it in my RCA Transmitting
Tube handbook but it isn't handy right now.  Depends on the filament
(pure tungsten, thoriated tungsten, oxide-coated, etc.).  On the
other hand, life is probably not much of a consideration in TC work
and some overvoltage is undoubtedly permissible.