Re: Cap problem-please enlighten me

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, May 10, 2002 5:36 PM
Subject: Cap problem-please enlighten me


> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<MrViper82-at-aol-dot-com>
>
> Hey All,
>
> I've been having some bad luck with my salt water caps. I used the geek
group
> method, one bucket with two 15/30 nst's in parallel.  I don't know why,
but
> after a while of operation the coil would completely stop working, even
the
> humming of the tranny's disappeared.  Come to find out, one of the corona
> bottles broke shorting out the two salt water plates.  This has happened
time
> and time again, currently I am down to nine bottles left in my bucket.
Anyone
> have a reason for this happening?

Glass is a pretty lossy dielectric.. What this means, in practical terms, is
that some of the energy that gets stored in the capacitor gets turned into
heat, rather than being returned to whatever the cap is hooked up to.  Say
the glass has a loss of 1% (i've no idea if this is a reasonable estimate,
by the way).  That means that of your 900W you're putting in, 9W is getting
dissipated in heating the glass. 9W isn't much as far as heating the water,
but if it were concentrated in one place, the thermal stress might crack the
glass. Once cracked, the bottle is history, because it will arc through the
crack and that will make it a LOT more lossy...

Hey folks with salt water caps... why don't you make some loss measurements?
It would useful to know some ball park numbers....  My antenna analyzer/RF
impedance bridge only goes down to 1.8 MHz, and some measurements at a few
hundred kHz would be more appropriate.  My transmitter only goes down to
around 500 kHz...