wrote:
I got bit by the genny bug again (happens every year at the start of
Thanksgiving ), and have been doing research on this year's designs.

Genny?

1) I have heard that using discarded pill bottles is a bad practice
due to the plastic spoiling the Q and having a low melting point.

Depends on the frequency, but pill bottles are not the best possible
material. Try styrene.

I have access to some kaolinite clay (porcelain) and a kiln. If I mold
and fire my own coil forms out of porcelain, what would be its effect
be on tank Q? And do I need to glaze it?

Porcelain should be self-glazing, because it vitrifies. It should have
a poorer dielectric constant than air, though.

The ITT Radio Engineer's Handbook has a table in chapter 6 that lists
constants for various materials.

2) Does anyone know how to bias a triode or pentode for high speed
switching?

How high speed do you want and why don't you want to use a gas tube?
With a vacuum tube, you pretty much have to run class C in order to get
complete cutoff. But what you want is a thing with a discontinuity in
the curve if your goal is to get a nice sharp square wave. That means
a thyratron, krytron or something. Then again, maybe you don't need a
nice sharp square wave.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."