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Re: Topband: alternative to vacuum variables

To: "Pete Smith N4ZR" <n4zr@contesting.com>
Subject: Re: Topband: alternative to vacuum variables
From: "Rick Karlquist" <richard@karlquist.com>
Reply-to: richard@karlquist.com
Date: Thu, 24 Jan 2013 17:39:41 -0800
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Pete Smith N4ZR wrote:
> One of the reasons I have mot gone to high power on 160 is the cost of
> capacitors for my omega match - at least $300.  Anyone know of any
> workable alternative?  I remember someone writing about using coiled-up
> RG-8, RG-213 or maybe Teflon coax.  Where can I find more information?

Making capacitors out of coax seems like an easy solution, however
they end up being fairly lossy due to copper loss.  Think about
it:  you would not deliberately make a capacitor long and skinny.
The only thing that makes them workable at all is that the heat
generated is spread out over a large area.  You would have to
carefully evaluate your proposed design to see if it were feasible.

Rick N6RK

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