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...And the reason I know the choke is lowering the impedance rather than increasing it is because when it rained the vswr went up from 1.3:1 to 1.7:1 @ 50mhz. But it then tuned at 1.3:1 @ 47mhz which is an increase in electrical length. The upper radiator cannot change because its aluminum so the electrical lengthening had to have come from the lower leg. If the impedance went up then the antenna would have been resonant at an higher frequency not a lower one. For it to be resonant when wet then the new electrical length has to terminate somewhere in the choke itself probably two inches or so into the first winding of the choke after the rain dropped the choke impedance probably from one mega ohm to maybe 0.75 mega ohms. That's just a rough guess. Why is it doing it? probably because air has a different dielectric property than water.