On 4/28/20 7:08 PM, Michael Tope wrote:
Yeah, I was expecting the two-coil design to have better VSWR bandwidth.
Did you compare the radiation resistance of the two designs? I would
expect the one coil design to have a lower radiation resistance.
Perhaps the lack of difference in the VSWR bandwidth of the two designs
explains why the Cushcraft 402CD/XM240 designs go to the trouble of
using capacitance hats after the loading coils.
capacitance hats make the current distribution more uniform along the
element - that helps with gain as Dave just pointed out.
A sort of ultimate version is a tesla coil - uniformly loaded, with big
capacitance on each end, with the "element" being a tiny fraction of a
wavelength. It's a parallel LC circuit.
Of course, a TC is a terrible radiator.
73, Mike W4EF..............
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