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 <[email protected]> wrote: Subject: Re: Topband: Vacuum variable capacitors To: [email protected] 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 > [email protected] > _________________ > Topband Reflector _________________ Topband Reflector _________________ Topband Reflector
