At 4:12 PM -0500 10/28/02, K3SV@aol.com wrote:
>Looking for ideas for counterweights for wire verticals, one end of
>the rope will be at a tower and the other end will be through a
>pulley. The pulley will be attached to a rope running through the
>top of a tree. Looking for what to put on the tag/free end, other
>than just anchoring it to something, considering these are big trees
>with big sway potential.
Not sure I understand your geometry; where does the wire vertical fit
into the picture?
The first step is to calculate how much tension you want in the wire.
IIRC, I found guidelines in the ARRL Antenna Handbook. For my ca.
70-ft. horizontal doublet of center-fed with 40-some feet of
open-wire line, I decided on 30 lbs. tension. I used a lead brick as
a counterweight.
In other applications I've used lead ingots that I bought at a local
foundry. Each weighs 62 lbs. For one antenna I used a 40-lb. ingot
of some kind of iron. Look in your local yellow pages. When you
don't care about the alloy or purity of the metal, you can get an
ingot cheaply. I like lead because it's easy to drill and install a
huge eyebolt in it. Remember that lead is soft and weak, so any bolt
or pin through it must be very thick so it won't pull out.
My present doublet has been up almost three years and has survived
impressive sticky wet snow, ice, and wind storms that have brought
down trees all around me, and have broken plenty of limbs off of the
trees that support my doublet. When the snow/ice load gets very
heavy, the doublet sags halfway to the ground and the lead ingot
rises pretty far, but nothing breaks.
Be sure that your counterweight is rigged so it can't snag on
anything, especially on its way up. Also, rig a light slack line or
two to keep it from swinging too widely like a pendulum when the wind
blows hard.
73 de Chuck, W1HIS
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