Similarly, you can parallel a lower capacitance air- or vacuum-variable with
the fixed micas. The ~100pf HV variables are much less dear. Same end result.
-Jeff
W0ODS
--------------------------------------------
On Tue, 10/22/13, Herb Schoenbohm <herbs@vitelcom.net> wrote:
Subject: Re: Topband: Vacuum variable capacitors
To: topband@contesting.com
Date: Tuesday, October 22, 2013, 8:51 AM
Steve, If you want to avoid the high
price of vacuum variables I would suggest the much lower
price of G2 or equal HV high current fixed micas available
on E-Bay. These fixed caps can be made essentially
variable by putting a series inductance like a hand wound
taped coil of copper tubing. You can also use a simple
roller inductor to find the correct march and then replace
with a fixed inductor of a higher power handling
capability. Be sure you pick a value that is somewhat
higher in capacitance then you think you will need so the
series inductance will give you an adequate tuning range.
Herb Schoenbohm, KV4FZ
On 10/22/2013 9:33 AM, D. S. Coleman wrote:
> GD All:
> This winter, my shack will have a new heat and light
source, thanks to
> the warm glow of vintage 3-500Z's on Topband.
:-) The downside is
> that now my variable capacitors in the the omega
match of my folded
> monopole will not be up to that kind of abuse. I
need to replace
> those old cheese slicer caps with a couple of vacuum
variables that
> are 500 pF or so max and a voltage rating of 5 KV or
better. Would
> any of you gentlemen have any vacuum variables that you
would be
> willing to part with? If so, please reply
off-list to my email
> address below.
> Tnx & 73,
> Steve, AB4I
> cwforever2@gmail.com
> _________________
> Topband Reflector
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Topband Reflector
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