[TowerTalk] Topband: Pulleys for antennas in trees

[Jim Brown]

On Tue,1/27/2015 9:50 AM, Mel Crichton wrote:
> So if using a pulley, please be sure the supporting branch is 
> stout.... I had to replace the windshield of my truck to prove this 
> point to me. I find it best to install inverted vee type (center 
> supported) dipoles or very light inverted L's to minimize the sideways 
> stress on the branch (sideways stress intensifies when the wind blows 
> hard). And yes I have pulleys high in trees. 

Hi Mel,

I can't dispute your mechanical engineering and rigging thoughts, but I 
strongly prefer flat dipoles if I can rig them. So does N6BT, the 
excellent antenna engineer behind the original Force 12 antennas, who 
observes that the performance of the antenna will be dependent on its 
average height.

Quite a few years ago, I saw a piece in QST stating that a lag screw 
going horizontally into the trunk of tree was one of the least invasive 
ways to rig an antenna. That means, of course, that someone has to climb 
the tree. My wire antennas are mostly rigged that way.

Since the subject line is about pulleys, I'll link to the pulley I use. 
It's a really neat pulley, and is sold out here by stores who cater to 
arborists and tree climbers.

http://www.cmi-gear.com/collections/frontpage-2-service-line-pulleys/products/rp115

Here's a photo of the pulley and the lag screw.

k9yc.com/Pulley.JPG

I use the 5/16-in rope distributed by Synthetic Textiles. DX Engineering 
and HRO also sell it. I use the 5/16-in size because it's big enough to 
be able to grab it hard enough to put a lot of tension on it. It's a 
double-braid polyester rope with a black outer sheath that provides UV 
protection.

  http://www.synthetictextilesinc.com/supportham.html

My wires are up 130 ft in redwoods, so they need pretty robust rigging 
hardware. Not everyone needs stuff this robust. :) Another important 
rigging element for any wire in a tree is a weight below a pulley 
terminating one end of the antenna to provide some "give" for tree sway. 
There are many ways to skin this cat, including old window weights and 
cement in a bucket. I use big water jugs that I fill with dry sand. I'm 
typically using 70-90 pounds of tension.

73, Jim K9YC