[TowerTalk] Topband: T - vertical improvement

[K4SAV]

KV4FZ wrote: ... Heres the trick..... if you need 370 pf as in the 
example quoted, put a fixed mica G2 of a higher value, lets say 500 pf.  
then add an inductor in series....

That will work if you provide some lightning protection for the mica 
cap.  When I tried this in Florida the cap would only last about 2 
months before a close strike would take it out.  You could probably get 
away with grounding the antenna when storms are near, although static 
buildup can be a problem for some people.

Even when you use a series air variable cap you need some protection for 
the cap.  When a cap arcs, little rough places are left which then arc 
over at an even lower voltage, and those spots are difficult to fix 
(impossible if you use a vacuum variable).  I do what you find in some 
linear amps, add a little spark gap across the cap set to just slightly 
less than the cap spacing.  Those are easy to repair.

Jerry, K4SAV
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