Hi Dale and the Topband group. To trim the vertical portion, and return to
original resonance every winter, I simply folded the wire closely back on
itself in a flat bundle at the feed point and taped it tight. The overall
length was shortened about 3' max.
Just pulling in the wire to reduce the droop of the horizontal leg didn't
appear to influence the resonance. Actual shortening by folding was required to
reset the resonant freq. I didn't cut the wire because I wanted the longer
length during pre-freezing conditions.
Tree-supported Inv-L's and "T"'s have their quirkiness versus true verticals in
the clear I believe.
73, Gary NL7Y
> Hi Gary:
>
> Thats interesting. But did you trim it every winter? In 20 years only half
> the antenna would remain. I'm not trying to be a wise-guy, just wondering if
> you trimmed it annually.
>
> You bring up a good point and that is that conductivity in a tree trunk may
> change when it is frozen.
>
> 73
>
> Dale - N3BN
>
>
> The following obs were an annual occurrence until my 85'+ support tree blew
> down this year. The 160 antenna described below was supported by the tree,
> and was no more than 4' from the trunk in the middle...the top an bottom were
> closer, ~1'.
>
> A wire Inv-L (#12 stranded THHN) with tuned elevated radials for 160, pruned
> in summer, dropped in resonance with each winter's freezing of the support,
> surrounding trees of similar height, and the ground below. It took up to 3'
> of vertical shortening (~2%) at the feed point to return it to 1.825, versus
> the same resonant point in summer.
>
> 73, Gary NL7Y
>
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Stew Perry Topband Distance Challenge coming on December 29th.
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