Peter asked...
> Question: Why do these modern ceramic tubes show negative screen
> grid current under some conditions? What is the mechanism that
> causes it? Straight thermionic emission from the screen seems
> unlikely, especially as a gold sputter would effectively prevent
> it.
It is caused by 'secondary emission' of electrons from the anode. Under some
conditions, more electrons are being gathered (by the screen grid) from the
anode
than from the cathode. For a bit more detail without going into the physics
and
mathematics of the phenomenon, see
http://www.r-type.org/articles/art-024.htm
for example.
I had remembered that this was covered in Eimac's 'Care and Feeding...', but I
can't
find it there now. That shows the state of my memory, I reckon.
73,
George T Daughters, K6GT
CU in the California QSO Party (CQP)
October 4-5, 2014
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|