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Rigging wire antennas in trees

Trees present a ready opportunity to support wire antennas. This article describes a method for rigging an antenna for short term or long term use, providing convenient access to the antenna system for maintenance, and without damaging the tree.

Tree Saver

The Tree Saver is a synthetic strap that can be rigged over a tree branch from the ground, providing a large bearing area on the branch so that it does not cut into the bark, or get jammed in the crotch of the branch. A halyard is rigged through rings on the tree saver, so the running rigging is relatively free.

Fig 1:


Above is a Tree Saver made from a length of 25mm synthetic webbing and two rings.

Place a ring on one end of the tape, turn back 200mm of tape against the standing part and tie a tape knot. Work the tape not down close to the ring and pull it tight. Do the same at the other end with the remaining ring.

You will need a Tree Saver for each tree attachment, typically two for a dipole.

Throw weight and line

Another piece of equipment is a throw weight and line.

Fig 1:

Above is a commercial throw weight of about 300g (used by arborists), and 3mm PE monofilament throw line (orange for visibility). The throw weight is a small streamlined bag of lead shot, and importantly, a ring that will not pass through the small ring on the Tree Saver.

Placing the Tree Saver

  1. Use appropriate Personal Protective Equipment (hard hat) and clear the area of other people. Keep a keen lookout for falling branches or rigging equipment.
  2. Test the stopper that will be used in retreival (see retrieval instructions).
  3. Choose a target branch. It should be relatively clear, strong live wood, provide a clear path below of retreival, and adequate height. With practice, you should be able to throw reasonalby accurately to better than 20m in height.
  4. Secure the end of the throwline to the ground, and place the throw line into a weighted bucket so that it can pay out freely without fouling.
  5. Attach the free end of the throw line to the throw weight, a bowline is a good knot, easy to tie and can be undone easily.
  6. Throw the weight over the target branch and let it fall to the ground. Remember which direction the throw weight crossed the branch, it is important.
  7. Untie the throw weight and pass the free end of the line through the smaller ring on the Tree Saver and tie it again to the throw weight. Make sure that the Tree Saver is not twisted.
  8. Untie the secured end of the throw line and pass it through the larger ring of the Tree Saver and resecure. Pull the surplus line through the larger ring so that the Tree Saver is ready to be raised.
  9. Haul down on the throw line to raise the throw weight. This will draw the Tree Saver up behind the throw weight. When the throw weight reaches the branch, give the line a sharp pull to flick it over the branch and immediately let it fall freely to the ground. You should now have the Tree Saver rigged over the branch and the throw line passing through both rings underneath the branch.
  10. Untie the throw weight and attach a halyard. Pull the halyard back through the Tree Saver to the ground.
  11. Making a closed loop of halyard is a good safety measure, but include a heavy ring or the like in the loop so that the wind does not blow the whole halyard up into the tree.

Needless to say, if you let go of the free end of cordage at some stages of this process, you may fail. Exercise common sense in securing cordage and suspended objects.

Rigging the antenna

Use the halyard installed to raise the antenna, and tie of the end securely. Allow enough slack for tree movement under wind etc. The halyard does not run sufficiently freely to use a weight to hold constant tension on the antenna, allow sufficient slack.

Retrieving the Tree Saver

  1. Use appropriate Personal Protective Equipment (hard hat) and clear the area of other people. Keep a keen lookout for falling branches or rigging equipment.
  2. Tie a stopper on to the end of the halyard on the side of the branch where the throw weight fell to the ground during placement (open the loop if you have make a loop). The stopper MUST pass freely through the larger Tree Saver ring, but NOT pass through the smaller Tree Saver ring. 
  3. Tie the throw line to the same end of the halyard. Don't skip this step, tempting as it might be, because it provides protection for a mistake in Step 1.
  4. Haul down on the other side of the halyard so that the stopper is pulled up to the Tree saver, and through the larger ring.. Continue hauling so that the Tree Saver is pulled over the branch. When the Tree Saver is clear of the branch, the throw line can be released, and the halyard used to pull the Tree Saver down, then to retrieve the throw line.

Warning

Do not use this Tree Saver to climb a tree, it is not sufficiently strong for that purpose. If you get your gear stuck up in the tree, find some other way to retrieve it.

Costs

At the time of writing:
So, about A$35 for throw weight and throw line, and A$4 per Tree Saver that you make.

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