Tony
Tom W8JI's comments are good, and my 2 cents is that your modeling
is "in the ballpark" concerning bandwidth, feedpoint Z and increased
loading inductance as it is placed higher on the structure.
I have built several short verticals for DXpeditions (including the recent
VP8GEO and upcoming TI9M). With each update of the design, I have
abandonded base loading coils as too lossy, then minimized all loading
coils in favor of inverted-L or T type top loading. I'll second Tom's
suggestion to increase the top loading with a larger hat or wires--you
will be a LOT happier with the results!
73 and good luck!
Gary, K9AY
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