Topband: Trees (not the N6TR kind)

[Gary and Kathleen Pearse]

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. 

Sure, the ground freezes deeper with each passing winter month, but once pruned a month after freeze-up in early November, it would stay that way and not change until a major warming briefly defrosted only the tree(s). Meanwhile, the ground below froze at ever increasing depth, to typically about 4' max. Real RF ground is 10's of feet lower in our Interior Alaskan soils.

I believe the tree(s) affected the wire antenna at some level. As to how much the RF was absorbed, or antenna pattern influeanced, I have no idea.

73, Gary NL7Y