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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