On 1/22/2019 12:58 PM, Bob Shohet, KQ2M wrote:
And where I have used 5/16”, the rope stays up forever.
The wires (80, 40, 30 dipoles, 160M Tee) hung between my very tall
redwoods mostly use 5/16" Synthetic Textiles rope, and mostly through
CMI rescue pulleys that climbers have attached to big hooks lagged into
the tree trunk. Over a period of 12 years, I have experienced serious
fraying of these ropes, three times enough to break the black outer
layer, requiring replacement of the rope, and once with the rope
breaking. For every antenna, one end rope is tied down to the tree and
the other end has a 90# weight that can move. I've replaced ropes that
break or fray with 7/16". Not cheap, but a lot cheaper than hiring a
climber for a day.
To put this in perspective, the highest of these wires are about 150 ft
up, the lowest about 100 ft, and all are fed with RG11. That's a lot of
weight, so it requires a lot of tension to minimize droop.
When I first moved here, K2RD used his pneumatic tennis ball launcher to
implement the method that N8DE described so well. It works, but I found
that I was giving up too much elevation, so I hired climbers. Another
important thing that climbers do is clear branches below the pulley that
could snag the antenna as it's being raised and lowered.
Raising and lowering is important -- every few years, I've had to lower
my 80M dipole with #10 THHN to trim a few feet, because it's stretched
with the tension. As I repair/replace these wires, I'm rebuilding them
with #8 bare copper from the big box store that W6GJB and I have
stretched to make it hard drawn. We tie one end to a tree trunk, the
other to the trailer hitch on his pickup, and slowly pull until it
breaks. We end up with 15-20% longer wire that's roughly #9.
73, Jim K9YC
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