>"Another technique that is often used for matching is to make the wires much
>longer than resonant (that is, resonant around the top of the BC band), so
>that the feed point Z is 50 +jX ohms (that is, inductive) on 160M, and tune
>the capacitance out by adding a capacitor of equal value in series. NEC can
>easily model this."
When over-resonating with a long T-top on 160m, the maximum current point moves
away from the ground and up toward the center of the vertical radiator --
another benefit. Unless there's a deliberate need to resonate on the
operating frequency (e.g., with some phased arrays), then over-resonating a
single T-top vertical radiator should be the objective, subject to the
availability of long, tall supports on either side of the vertical section.
As the resistive component of base Z increases, matching network losses are
minimized, especially if the T is tuned to 50+jX as K9YC cites. Then, network
loss is a function of C, the only matching component needed. Make it a vacuum
type, and matching loss is very low.
When the T-top is resonated into the BC band, be prepared for some very high
base voltages if it's located anywhere near a BC station at the top of the BC
band. The better CIA and VNA devices can be operated in these conditions and
still provide valid measurements.
Paul, W9AC
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