Topband: Vacuum variable capacitors

[Herb Schoenbohm]

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