Variations on a theme, I know, but if you want to avoid having to
re-shoot a line into a tree OR hiring a tree climber pretty much ever
again... at least minimize the chances, you might want to consider what
I have done with my 80 meter loop suspended from 2 trees and a mast (3
trees the same).
Lift System:
1) Use pulleys, as described before., but don't have someone climb the
tree and put the pulley on a fixed harness in the tree.
Put the pulley on a rope that travels over the branch/notch, whatever at
the height you need it. Use AT LEAST a 4 inch sheave (not OD, but
groove diameter) to minimize work hardening on the copper wire strands
and to make it easier for the antenna wire to move around as the trees
sway. I use a pulley on a rope at ALL THREE lift points for the loop.
2) On your lift ropes, use a steel "leader". Aircraft cable with
plastic coating or an added plastic cover tube for the section that will
rest over the tree contact. I made my leaders approximately 12 feet
long so I could vary the distance from the tree that I locate the pulley
in order to equalize leg length and/or included angle between adjacent
antenna segments. The aircraft cable keeps the tree from abrading the
rope, and the plastic coating keeps the cable from digging into the tree.
3) Use a quality braided polyester rope stock for the rest of the line,
and include plenty of extra on each lift point. That way, you can lower
one or more points of the antenna for maintenance or adjustment. I use
a wood thread studded "eye bolt" at about 8 foot up on each tree as a
rope guide AND also as a "keeper" to keep from losing the rope in an
emergency. Attach something permanently to the end of the lift rope
that CANNOT pull through the eye bolt. (8 feet gets them out of head
banging distance and gives plenty of weight lift distance for high winds.
4) Weight(s): I use a weight at ALL lift-points. In my case, I am using
a full 25 pound bag of lead shot at each of three corners. It just
happened to work out that 25lbs per corner is in the range that keeps
proper tension on the line and stays on the ground in calm conditions.
Too much weight and the tree sways will not lift the weights and the
antenna wire bears all the added stress and may break in high winds.
Not enough weight, and light wind will lift your weights and maybe get
them fouled. I wrap the canvas bags of shot in TWO unopened contractor
bags (black) as protection from the weather.
To the weights, I tie one of stainless steel loops with the
screw-open/closed gaps for easy line insertion and removal. The lift
rope comes down to the weight, through the loop on the weight and then I
can pull UP on the rope to set tension to just below the lift-off point
for the weight. Then, I tie the rope off AT the loop with several turns
and a figure-eight knot with a bite pulled through so it can be pulled
loose easily. I put a stick/dowel through the bite and snug the bite up
with the free end to make sure it doesn't pull free. You use the stick
to open the bite for stick removal when you need to free the rope.
Then, I coil the free running end extra footage up and secure it off the
ground... either on top of the weight or hooked to the eye bolt up at 8
feet.
5) Pulley: To minimize weight in the lift system, I use a 4" plastic
pulley I found at Home Depot. It has a riveted shaft through the sheave
and into the flanges... I drilled this out and replaced it with a
proper stainless steel bolt of sufficient length that no threads extend
beyond the nylock nut I used. I used washers to properly space the
sheave from the flange to keep the flanges square and the sheave free
running. This pulley happens to have a metal bushing pressed in. If
yours does NOT, you'd be well served by machining the sheave as required
to add a bushing to ride on the shaft bolt. I then coated the shaft and
bushing with a "stay put" type grease. Paint the pulley sheave black
and it will disappear into the canopy. This pulley is intended for
laundry line use, so it does well in the sun.
Antenna Maintenance:
Because I can independently lower each corner a little or a lot as
desired, I can lift the antenna into place WHILE negotiating around
various impediments (branches mostly) that I do not have the ability (or
legal authority) to cut away. And I can bring the entire antenna down
to periodically check for wear, work hardening, adjust length,
maintenance the feed point, et al.
With the antenna pulled partially down at the three corners, I can pin
the feed point to the ground and mark the resting positions of the wire
ends at the feed point. Then, I can disconnect the feed point on both
sides, attach my spare reel of wire to ONE end of the old wire, and feed
a NEW wire into the system simply by pulling on the other end. Once the
new wire is fed all the way around, I can simply cut it a little long,
feed the two fresh ends into the feed point bracket and adjust so that
the wire rests in approximately the same relationship as the old wire.
Then, fix/solder/weatherproof one side, and temp connect the other side
where I am pretty sure the length is the same as the old wire. Lift into
position and run it on the VNA... Pull it down and adjust length
(although the one replacement I have done required none), solder and
weatherproof the second connection. Lift back into position and I am
done. I can replace the antenna wire in under 30 minutes.
Lift Rope Replacement:
ONE corner at a time. Lower the pulley to the ground. At the free end,
attach a NEW spool of rope to the free end (you'll have to remove your
pull-through guard). Once secure and preferably taped into a smooth
transition, pull the NEW rope over the tree point from the pulley end.
When you get the new rope end in hand, secure BOTH ends of the NEW rope
together about 4 foot up to make sure it doesn't go anywhere. Attach
the NEW rope end to your leader/pulley assembly, and then disconnect the
OLD rope. Cut the free end, burn it and attach your pull-through guard
to the end. Remove the attachment (hand-over loop with a bite works
good) that secures the new rope ends together at the 4 foot mark. Now,
simply lift the antenna with the new rope and secure to the weight as
described above. Repeat "N" more times...
Wire replacement: I am an OVER-maintainer, but I replace the lift ropes
ever 3 years, and will replace the wire every 5 years. You can stretch
these time periods to your personal comfort level.
Long and wordy... but I hope someone finds it of use...
73,
______________________
Clay Autery, KY5G
(318) 518-1389
On 17-Jun-18 13:04, Jim Brown wrote:
Lots of great advice in this post, and also the one from N5WA. An
important shortcoming of the substituting carabiner for the pulley is
that as the trees sway in the wind, there will be much greater wear on
the support rope, and it will eventually break. FAR better to attach
a pulley to that rope using the method you describe. K2RD showed me
that trick soon after I moved here.
Another important point is that the rope for one end of a dipole must
be tied to a weight that can move up and down with tree sway. There's
a lot of tension on a dipole at 140 ft fed with RG11, so it takes a
lot of weight. I use a large water jug filled with dry sand (about
90#). Lacking that moving weight, the antenna will end up on the
ground sooner rather than later. I learned that the hard way when I
had an antenna rigged between two pulleys but didn't yet have a weight
ready to put on it. Lots of wind a week or so later, and it was on the
ground.
The quality of the pulley also matters. This is the one I use.
https://www.cmi-gear.com/collections/arborist/products/rp115?variant=633842217
Climbers love it because the sideplates rotate so you can lay the rope
into it rather than having to feed it through. Marine pulleys are also
a good choice.
73, Jim K9YC
On 6/17/2018 8:02 AM, Bob Shohet, KQ2M wrote:
When the carabiner is in the desired place in the tree, simply secure
BOTH ends of the carabiner and then pull up the other rope through
the carabiner with the antenna attached.
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