One thing I considered when hanging my dipole was the breaking strength of
the wire used on the antenna vs that of the rope. Over the 5 years the
antenna has been up, the rope has been entangled in either poison ivy or
bittersweet vine (both are ubiquitous and voracious in my yard) and doesn't
move well, but my thought was that I'd rather the rope break than the wire
for the antenna. Storms like we got this past weekend here in New England
are rough, pullies can freeze up and the winds were high.
Obviously if you're using really heavy wire this is elss of an issue, I've
got the 13AWG copper clad steel from the wireman and it's been pretty
solid.
Sean WA1TE
On Tue, Jan 22, 2019, 16:45 Jim Brown <jim@audiosystemsgroup.com> wrote:
> 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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--
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