I built a 160 meter amp 12 years ago using 3 813's
connected as cathode fed triodes and they still play fine, 900 watts
output.
Mark Graalman WB8JKR
On Wed, 11 Feb 1998 11:00:11 -0700 John Lyles <jtml@lanl.gov> writes:
>Someone (sorry!) said:
>>> >I also note that Svetlana now makes an 812 tube. Not sure how
>they
>>> >compare to 811's, but recall they are a hotter version of the
>same.
>>> the 812 is similar, but has a substantially lower Mu.
>>I was really thinking of the 813. Don't think Svetlana is making
>>that, though.
>
>
>Yes, 812 would be hard to drive(lower gain). 813 is beam power tube
>(tetrode),
>not triode. Maybe it could be connected grid to screen and run in
>triode
>mode, although
>it may be easy to overdissipate the grid in such a circuit. Is there
>experience here with using 813 in triode connection?
>
>I have an old power oscillator (sort of an ultrasonic driver) that I
>got
>from GSA auction years ago, and it has a pair of 813's in it. It
>drives 10
>Khz at 300 watts or so, and had a nickel magnetostrictive transducer
>at one
>time, to separate blood cells! (according to the paperwork from
>Raytheon).
>Since it is in a rack chassis and has the screen and plate power, I
>was
>going to do an HF amplifier with the thing, many moons ago. now it
>sits in
>dust and bugs in "the shed", next to the diathermy machines (another
>subject!).
>
>John
>K5PRO
>
>
>
>
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>
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