Stated an impedance ratio, the PI tune capacitor, the load capacitor
and the coil have only one solution for each chosen Q.
To mantain the same PI circuit, lowering plate voltage requires a
decrease in plate current but this reduction has to be produced
reducing drive power and not varying tune or load capacitors.
Leaving the same L but varying Q there are virtually infinite solutions
of tune and load that comply the required impedance ratio, but then,
plate capacitor can't be that found for another Q.
It's proper to remember that plate capacitance is the sum of tune
capacitor and tube output capacitance.
With some active devices the reactive component in the output impedance
may vary because of the flowing current in it and tune capacitor may
vary althought R stay the same.
73,
Mauri I4JMY
> ---------- Initial message -----------
>
> From : owner-amps@contesting.com
> To : amps@contesting.com, Wt8r@aol.com
> Cc :
> Date : Sun, 8 Oct 2000 19:02:54 -0400
> Subject : Re: [AMPS] A Question re Power Levels
>
>
> > If I operate my amplifier at it's rated maximum power input of 4
KW (into
> > a dummy load), and the (hypothetical values) plate impedance is
2000 ohms
> > and a Q of 12. The tuning capacitance is 45pF and the fixed
inductance
> > value for that band is 4.5uH.
> >
> > If I reduce the Ep to 3000 volts and adjust the loading, etc. until
the
> > anode current gives me a plate impedance, again, of 2000 ohms, will
the
> > tune capacitor (again) resonate at 45pF? If the tune capacitor
value is
> > different, what factors will affect the difference?
> >
> > Thank you for your input on this subject.
> >
> > Dave, WT8R
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