This is a real simple question, I suspect.
When I operate my SB-220 into a dummy load on 40M, the loading capacitor is
at approximately mid-scale. The dummy, a cantenna, measures about 1.04 SWR
on my VFD, so I assume it is ~50 ohms+/- j0. When I attach my real yagi to
it, at the same frequency, where its SWR is virtually the same, the loading
cap wants to be full clockwise for maximum output.
My question is, what is this telling me? Does more capacitance in the
output of the pi (than the dummy load value) indicate inductive reactance
on the feedline? Would a requirement for less capacitance indicate that
the feedline was capacitative?
Reason for asking is that I replaced my top guys with Phillystran yesterday
and to my surprise, the tuning of my 40m yagi seems to have changed
drastically. Tune capacitor setting is somewhat different than before, as
well. Lowest-SWR frequency moved up about 50 kHz, but the SWR bandwidth
and approximate values vs. frequency haven't changed.
Sorry, I know this is kind of a straddle between amps and towertalk, but
here it is...
73, Pete Smith N4ZR
Contesting is ... Extreme Radio
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