On Tue, 2009-05-19 at 23:22 -0400, Richards wrote:
> That is my understanding, as well.
>
> I believe the better setting on the Pi network, i.e., Palstar, tuner is
> to pick the one with the highest Output capacitor setting, and lowest
> Input capacitor setting.
Not really. That condition is the one with the highest impedance
transformation which is not necessarily the condition for a match. The
impedance ratio is proportional to the ratio of the capacitor values
providing the load is resistive. If the load is reactive, and most
antennas are, then the reactance of the load directly affects the output
capacitor setting by adding or subtracting from the value needed for the
impedance transformation.
Loss in a PI tuner comes from running a high loaded Q causing much
circulating current in the coil and capacitors. The lowest loaded Q is
when the input capacitor has minimum value for the particular load and a
matched condition. And the lowest loaded Q will give the best tuner
efficiency.
You get no choice of loaded Q in an L network, the Q is determined by
the impedance ratio which gives it only one tuning condition.
> But you do have to work a bit longer to
> determine whether more than one setting works, and which one that is.
>
> But if the end result is the essentially same, then I am not sure I want
> to pay much more for the TT - I might better spend my hard earned brass
> on the auto tuner - or a remote tuner for the base of my big stick
> vertical antenna.
I think most automated tuners are L rather than PI or some other tuner
circuit because the L takes the fewest variable components and has that
one unique tuning for each load impedance. The automated tuner includes
the capability of connecting the tuning capacitor to input or output
depending the load impedance.
>
> Thanks for your view.
>
> =========== Richards - K8JHR ===============
>
73, Jerry, K0CQ
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