Topband: Antennas in trees

Gary and Kathleen Pearse pearse at gci.net
Wed Nov 14 21:04:43 EST 2007


Here's some info of interest regarding antennas and trees from K9LA  
that may have already been discussed:

http://mysite.verizon.net/k9la/sitebuildercontent/sitebuilderfiles/ 
low-band-antennas-and-trees.pdf

In Fairbanks, my 160M Inv-L goes up 80' and out 56.5' with a SWR of  
1.3:1(about 38 ohms) is resonant @ 1.825 mHz with three 128.6'  
resonant radials of #14 THHN elevated at least 15' over poor soil on  
a 120' sq. city lot. These values did not change after freeze-up, so  
I assume the tree's influence (they're White Spruce) also didn't vary  
much. However, when using 120 ground-mounted radials in the past at  
my other shack out in the woods on a similar length/design antenna, I  
would note a small shift in resonant frequency and SWR as the ground  
and trees froze. I assumed that was due to earth conductivity  
changing below the ground plane and horizontal portion of the L- 
element. When the wind blew hard, and the trees wobbled, the SWR  
would also walk around a bit until the wire inevitably broke (:-(

73 Gary NL7Y in Fairbanks


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