Hi John...
Here's a pragmatic approach to spring selection...
1. My support lines are rigged right over the tops of the trees... up
high where the branches are slender (1/2 inch diameter range). At that
size, branches are still strong enough to withstand the tension needed
to pull the antenna flat, and yet are flexible enough to act as natural
springs protecting the antenna.
2. These support lines are typically 3/16 inch braided nylon. This has
plenty of strength, plus good abrasion resistance. They normally survive
at least three years before scuffing through. I could care less about
that, 'cuz my antenna is a wire vee beam, which I re-aim frequently to
different headings... often enough that I usually see a scuffed line
before it needs changing.
3. From the top ends of the support lines I run 1/16 inch diameter
braided nylon mason line from just clear of the tree-tops out to the
ends of the antenna wires. The actual antenna wires are #14 AWG solid
soft-drawn copper, each leg just under 100 feet long. I use #14 because
it is relatively inexpensive, it's strong enough to survive, and light
enough you can pull out the sag without over-stressing anything.
Everything else equal, heavier wire sags more. And... height is of the
essence for DXing.
4. By now you may be thinking *NOT STRONG ENOUGH*. If so, I respectfully
disagree. I live in ice storm alley, just across the border from upstate
New York. Every winter we have at least one major ice storm (major = >
1/2 inch radial ice, plus winds in the 70 km/hr range.) In the seven
years I've used this antenna system, I've had three masts taken down and
over 500 trees severely damaged by winter ice. However, in that time
there have been *ZERO* failures of antenna wires or support lines.
5. This is due to two things... 1. The natural springiness of the
treetop branches, and 2. The springiness of the mason line, which will
stretch at least 10% before it comes anywhere near breaking. Together,
these are stiff enough to pull the #14AWG flat, but springy enough to
prevent breaking it. So no need for "real" springs, or pulleys etc,
which always ice up solid anyway.
6. BTW, this Vee beam is a penniless DXer's delight... loud, inexpensive
and easy to maintain. When looking down the hill toward Africa and South
America, it models >15 dBi (think 5-el yagi) below 5 degrees elevation.
The bad news is: it's an absolute pig to rotate, 'speshially on a stormy
winter's night... hi! But I love it.
73 + GL!
Rod Elliott VE3UW
DXCC HR, etc.
John King wrote:
> Has anyone found an appropriate spring for protecting dipoles when the
> supports such as trees sway? Maybe a name hardware supplier has such a spring?
>
> I am going to use Dacron with a strength of about 750 lbs, to suspend the
> wire antennas, and would like to be able to pull the vertical loop and
> dipoles strung between trees taunt and at the same time protect the antennas
> from breakage. I am sure the rope is much stronger than the copper wire that
> will be used.
>
> The spring must be strong enough to hold the antenna taunt YET give enough to
> protect the antenna.
>
> I am going to use old water hose on the Dacron where it goes over the limbs
> to prevent scuff damage to the Dacron. Also, I like the idea of using a
> weight on the tail of the Dacron near the earth to allow movement of the
> trees without breaking the Dacron. The weight can be judiciously selected to
> keep the antenna taunt and still provide give for the line.
>
> Your suggestions will be appreciated. 73, John, K5PGW
>
>
>
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