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KI4ITI
06-26-2009, 05:02 PM
I'm about to put up a couple of dipoles using trees as end supports. The most sensible scheme I've heard of for doing this involves attaching a pulley to the tree and then tying the end of the support rope to a weight so that the tree can move in the wind without causing problems.

Anyway, I went to Lowe's the other day and didn't see anything in the pulley bins that seemed obvious how you would attach it to a tree. Most of them looked like they were designed to hang, and had ring/swivel mounts.

What suggestions, then, for pulleys to use and methods of attachment? BTW, the dipoles will also be center-supported... which will alleviate some of the load on the endpoints. And, this will be a semi-permanent home install, not a FD setup.

Thanks and 73
Josh KI4ITI

WB2WIK
06-26-2009, 05:04 PM
Use a rope to haul the pulley up into the tree, tie the rope off down low so you can lower it again if and when needed.

Make sure the "antenna rope" is through the pulley and reaches the ground first, of course!

Make no "connection" with the tree, it's unnecessary and can harm the tree.

A rope over a tree limb to hold the pulley up there works just fine.

WB2WIK/6

KA4DPO
06-26-2009, 05:07 PM
One other way to do this is to use screen door springs between the rope and insulator. They will provide all of the stretch you need and will last for three or four years depending on weather conditions.

W3BNY
06-26-2009, 05:29 PM
Ive got a picture somewhere at home of what can happen when you put BARE dipole ends into a paper bark tree and run a KW thru it!!! :eek: It was posted here a while ago.

I'll find it and post...

KA5ROW
06-26-2009, 05:45 PM
The end goes through a plastic insulator, from there to a nylon string. The string is tied to a spring to let the dipole have some give in the wind and allow the tree to move without stress on the wires. :D

G4ALA
06-26-2009, 08:13 PM
Here is what I hope will be a helpful thought.

Provided the dangling weight is heavy enough to overcome the friction inside one of the eyes of a plastic dogbone insulator, try the following:

Get a small diameter (3-4 mil) rope over the branch of a tree. Such polyester rope is sold as low cost washing line in the UK. Get the two ends of the rope together, tie them with about 6 inches to spare at each end on either side of the knot. Tie a first dogbone insulator through one of its eyeholes onto the knot using the spare lengths at either end.

Next, thread a second rope through the other eyehole of the first dogone insulator. Keeping hold of one end of the second rope, pull on one side of the first rope to raise the first dogbone insulator to the height of the branch, at the same time letting the second rope feed through the other eyehole of the fisrst dogbone insulator so that you are left, at the ground, holding both sides (ends) of the second rope. Tie off the first rope near ground level to secure the first dogbone insulator at the branch. The first dogbone insulator acts in place of a pulley wheel.

Tie a second dogbone insulator to the two ends of of the second rope in the same way using a first eyehole of the second dogbone insulator. The second rope, passing through other eyehole of the secured first dogbone insulator, can be hauled up and down to raise and lowerthe second dogbone insulator.

Thread an antenna rope from the end of the antenna through the other eyehole of the second dogbone insulator. Tie a weight to the end of the antenna rope. Raise the second dogbone insulator using the second rope so that the second dogbone insulator joins the first dogbone insulator at branch level. Tie off the second rope near ground level to secure the second dogbone insulator. If your lengths are OK, the end of the antenna rope should be in the air with the weight dangling from its end. If not, pull the second dogbone insulator down and adjust the length of the antenna rope until it does.

When the tree sways, the antenna rope will slid in and out of the other eyehole of the second dogbone insulator. This will eventually result in attritional wear to the inside the other eyehole of the second dogbone insulator. When this happens, sinmply use the first rope to bring down the first dogbone insulator and replaced the second dogbole insulator.

No pulleys or damage to the tree needed!

73

John
G4ALA

K3STX
06-26-2009, 08:26 PM
You are overthinking this. Don't bother with a pulley, just throw the rope up into the tree, over a branch, and then down to the ground. (Actually, I throw a fishing line over the branch, tie a rope to the sinker-end, then reel it in, thus bringing the rope to where I am standing. Then I attach the dipole end, go back to the END of the rope, and pull it up). So the rope is directly on the branch. EVENTUALLY the rope will break from abrasion. Then you simply replace it. But I have had mine up in the air for 3 years, and we get 40 mph winds all the time.

paul

K0RGR
06-26-2009, 08:26 PM
I've seen another option a couple times of using weights on the end of the line holding the dipole up. Choose the weights to be just big enough to do the job of keeping the dipole relatively taut, while allowing the tree limbs to sway in the wind.

I'm thinking about using this method myself soon.

NN4RH
06-26-2009, 08:41 PM
You are overthinking this. Don't bother with a pulley, just throw the rope up into the tree, over a branch, and then down to the ground. (Actually, I throw a fishing line over the branch, tie a rope to the sinker-end, then reel it in, thus bringing the rope to where I am standing. Then I attach the dipole end, go back to the END of the rope, and pull it up). So the rope is directly on the branch. EVENTUALLY the rope will break from abrasion. Then you simply replace it. But I have had mine up in the air for 3 years, and we get 40 mph winds all the time.

paul

Same here. No need to overintellectualize this or make it more complicated than necessary. No pulleys or weights or springs. Just toss the rope over the tree and tie it off around the trunk.

LIke Paul I slingshot a fishing line over tree but then tie it to a roll of masons string and pull that over, then use the masons string to pull the antenna rope back over.

Just don't tighten the heck out of it, and it will be fine. The smaller tree branches will themselves act as springs.

The difference in pattern between a slightly sagging dipole with some slack in the ropes, versus a perfectly straight one under a high degree of tension is negligible.

Use a 3/16 inch or heavier nylon rope. I've had dipoles in my trees continuously going on 6 years now with no troubles despite ice storms, thunderstorms, high winds, and a multitude of squirrels.

And if one ever did break and fall down, it would take all of about 5 minutes to put it back up.

NA0AA
06-26-2009, 08:58 PM
I'm going to assume you want a long-term antenna and do not want to do injury to the tree:

Drilled anchors - I use a closed eye lag bolt, then a threaded link to hold a garage door pulley. If you allow room for tree growth, 5 to 7 years is a reasonable lifetime for such an anchor.

How to do this is described in the ARRL Antenna books.

I have a permanent pully with a halyard that hoists a second pully that has one end of the dipole support rope threaded thru it down to ground level, then I have a 10lb iron weight to act as the tensioning load for the dipole. Mine has survived quite a few blows now - the only time it fell down is once when the counterweight itself failed - I fixed that w/out leaving the ground. On a windy day, that little counterweight gets a ride, but the antenna survives nicely.

A rope over a limb can wear a notch in the limb or the limb can grow over the rope or wire which can impair the health of that branch. You also cannot use a loop of wire/rope around the trunk as a permanent anchor for the same reason - the tree will grow around it eventually.

Now for temporary use - field day, a week or two temporary OK, but I love my trees too much to do 'em more harm than a couple of small holes. Without my trees, I'm stuck with verticals, after all.

G0GQK
06-26-2009, 09:26 PM
There were men walking on the Moon 40 years ago, there are unmanned aircraft in Afghanistan firing rockets controlled by technicians in Texas or wherever, and people ask, and others describe, how to tie a length of wire to a tree !

G0GQK

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