On 10/21/2013 11:42 AM, larryjspammenot@teleport.com wrote:
I want try this broadband 80/75-Meter dipole someday when I get some support
lines over a few of my tall fir tree branches.
Originally in the April 1989 QST, reprinted in the NCCC
newsletter:http://www.nccc.cc/jug/2011/jug11jul.pdf
This is a good design for use as a center-supported inverted Vee, where
there isn't much mechanical stress on it, but I wouldn't want to rig it
as a high flat dipole between two trees. For that application, plain
ordinary big copper using the transmission line matching I suggested is
a far better way. I use either #10 THHN (house wire) or #8 bare copper
that I've stretched to make it hard drawn. The advantage of the latter
is that it doesn't stretch any more.
Putting some numbers to it, I've got about 100# of pulling tension on
the support ropes (in the form of pulleys and a 100# water jug filled
with dry sand to adjust for trees swaying in the wind), and the dynamic
stresses of a typical winter storm are much greater. It costs me > $1K
to get climbers to rig a pair of pulleys up in my tall trees with ropes
through them and trim enough limbs to give the rope a path. The last
thing I want to do is have to pay them to do it again when it breaks.
73, Jim K9YC
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