[Amps] Air Gap

[Rich]

I understand things better after I build something, I think my skull is
a little thick at times. That is why for my first amp will be a monoband
for 15m and maybe 20m with a change in coils. If it works then I might
try one for 10 thru 40 with a band switch. Rich now my only beam ant is
a 15m monobander, everything else is wires or vertical.
Rich

Subject: Re: [Amps] Air Gap

Rich:

Sounds like a fun project.  I would strongly recommend a vacuum variable
capacitor for the plate side shunt.  The main advantage of vacuum
variables is their high max to min ratio.  The problem with 4-1000s is
that with their high plate voltage, and high cout, it is tough to build
a
managable high impedance tank circuit that will still work on 15 and 10
meters.  The high impedance tank demands that the plate shunt
capacitance
be kept as low as possible, hence the vacuum variable.  Of course,
keeping your plate potential lower will help too in keeping the plate
impedance down, resulting in higher tank cap values.

You may want to trade-off a pi-L vs. pi to determine which results in a
more "benign" plate shunt cap.

73, Steve K0SF