Topband: de n7dd

[Guy Olinger K2AV]

Issues of a fixed capacitor as seen in this thread have been a similar
problem for a network two-banding an 160m Inv L over FCP.

k2av.com has a section on this problem how to do 500 with three 170 pf
barrel style HEC caps. The section also has links to HEC reference material
on how to derate those capacitors, also links to a number of suppliers.
Click on green index button "160+80 on One L/FCP".  Do a find on "80M
Capacitor".

The calculations in the k2av.com text are at 3.5 MHz. The reference
material will need to be exercised for 1.8 MHz.

The HEC 170's seem fairly plentiful with better prices than other cap
values.

73, Guy K2AV

On Fri, Jan 10, 2020 at 2:22 PM Mike Waters <mikewate at gmail.com> wrote:

> An air variable is exactly what I was thinking, Dave.
>
> My 160m inverted-L tuner uses just two air variables. I padded the HV
> variable with a small 100 pf N1500 (or two) doorknob with no problem.
>
> I use those same doorknobs as padders in my HB legal-limit amplifier, but
> they do cause the tuning to drift. :-(
>
> I have also seen fixed-value HV vacuum capacitors at hamfests.
>
> 73 Mike
> W0BTU
>
> On Thu, Jan 9, 2020, 3:15 PM David Olean <k1whs at metrocast.net> wrote:
>
> >
> >  ... What about an air variable in a wx proof box?
> >
> >
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