Topband: Vacuum variable capacitors

[Jeff Woods]

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

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On Tue, 10/22/13, Herb Schoenbohm <herbs at vitelcom.net> wrote:

 Subject: Re: Topband: Vacuum variable capacitors
 To: topband at 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 at gmail.com
 > _________________
 > Topband Reflector
 
 _________________
 Topband Reflector