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Pyrex diss. factor
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From: Edward V. Phillips [SMTP:ed-at-alumni.caltech.edu]
Sent: Saturday, February 28, 1998 10:55 AM
To: tesla-at-pupman-dot-com
Subject: Re: Pyrex diss. factor
"Glass of all types has large R.F. absorption ie high power factor and
as such is a poor choice for any part in a Tesla coil! The same poor
performace yielded from salt water/bottle capacitors and glass plate
capacitors can be expected from using glass as a secondary form! Much
better to use PVC or better still polyethylene or the best of them all
Teflon! Although the last one will bankrupt you for sure. Heck even well
baked out cardboard tubing that is saturated with polyurethane and allowed
to dry under heat is superior to glass!"
Not inclined to agree. My guess is that you couldn't find any
measurable difference in the unloaded Q of a coil wound on a glass
form of typical TC dimensions and one wound on polystyrene, which is
a much better insulator. There just isn't enough of the electric
field in the form to make much difference. By the way, my copy of
"REFERENCE DATA FOR ENGINEERS" lists the dissipation factor of
pyrex as 0.0036 at 1 MHz, which isn't bad at all.
Ed