Steve,
My lot is heavily wooded and I use wire verticals on 80, 40, and 30 meters. On
160M, I shunt feed my 80 foot tower. Some of trees go up to 115 feet.
I have two 40 meter wire verticals, a ground plan and a "Half Square." Initally
I had one end of the Half Square suspended from the tower and the other by a
tall cedar tree. It showed 4 to 6 db advantage over the 40M ground plane (which
hangs from a very tall tree branch.)
The Half Square was affecting the tower match on 160M so I moved the Half
Square to some tall trees away from the tower. The result, confirmed by
numerous comparative signal reports, and PSK reporter, shows at least a one S
unit deficit to the previous location away from the tall trees.
Secondly, the SWR was affected. Before the weather turned cold, the Half Square
SWR was about 1.6 to 1 (fed at an upper corner). Now with colder weather and
falling leaves, the SWR has dropped to 1.2 to 1.
In summary, I suggest keeping the vertical wire as far away as you can from the
trunks of tall trees. I believe that tall trees are definitely detrimental to
the operation of low frequency transmit verticals. I also see this affect on my
shunt fed 160M tower as the trees leaf out in the spring and lose their leaves
in the fall.
73, Dennis W0JX
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|