Thanks to all who responded. Summary:
Adding a second beam above first one had little or no effect on resonant
freq or SWR.
Improvements suggested that I can effect here are:
Add RF chokes to the insulated beam elements, such that elements are
grounded at 1.8mhz, but not at HF.
Add stingers to ends of beam boom for added capacitance/inductance. (this
may also enhance low-angle radiation)
Insulated beam elements may be coupling, for more capacitance than I
thought.....Check tower resonant freq.
The above seems to confirm ON4UN's statement that, indeed, the operative top
hat capacitance is connected with ground capacitance. Apparently natural
skin effect capitance of the tophat itself, as in space, is insignificant to
the tophat/ground capacitance effect.
73, Doug / Nx4d
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