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Pyrex diss. factor


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From:  Alfred A. Skrocki [SMTP:alfred.skrocki-at-cybernetworking-dot-com]
Sent:  Friday, February 27, 1998 1:04 AM
To:  Tesla List
Subject:  Re: Pyrex diss. factor

On Wednesday, February 25, 1998 1:38 PM Edward V. Phillips
[SMTP:ed-at-alumni.caltech.edu] wrote;
>> "Jim,
>> 
>> I checked "Dielectric Materials and Aplications" by von Hippel:
>> Pyrex (Corning 7060 - Soda-borosilicate) has a loss tangent of around 28
>> in the Tesla Coil frequency range of 10^5 - 10^6 Hz. Alkali-Silica glass
>> (12.8% Na2O, 87.2% SiO2) comes in at around 240-159 in the same
>> frequency range, and soda-lime silicate is similar, but a bit lower for
>> the same frequency range (140-100).
>> 
>> Jim, I also suspect that, other than doing an actual measurement of
>> secondary Q, you'd be hard pressed to distinguish any performance
>> difference between these as a Tesla Coil secondary coilform.
>> 
>> Safe coilin' to you!
>> 
>> -- Bert --

> "
> 
>  One big difference!  The Pyrex won't carbonize in the event
> of breakdown, and won't be likely to crack with the heat either,
> so it (the glass form) should be more or less indestructible.  Of
> course, it will be pretty heavy,,,,
> 
> Ed

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!

                                       Sincerely

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