How to Hang a Dipole Antenna
I recently purchased a W8AMZ 80-6M OCF dipole. It works pretty well, but performance varies depending on the installation. More on performance in a later post; for now, I will discuss how I installed this antenna using my 50# recurve bow. Needless to say, this post assumes that you know how to shoot a recurve bow. Be careful when shooting the fishing line; make sure it doesn't get tied around either arm (the arm holding the bow, or the arm pulling the string).
I live in the mountains near Scotts Valley, amid towering Redwood trees. Fortunately, the lower limbs of the trees around my property are trimmed, so the lowest limbs can be 30-60 feet high. This makes for a decent height to hang a dipole antenna! The one caution here, though, for my situation, is that Redwood limbs can't hold a lot of weight. I have had a few break when I pulled too hard on the rope, since they are brittle. I have also heard that in the Summer they can get even more so. Throwing caution to the wind, let's get started.
The items shown: my 50# recurve bow, a finger guard,protective eye wear, 100 lb fishing line, a pulley, and an arrow modified for hanging rope high in the trees.
It is an aluminum shaft arrow, with the regular tip removed. In its place, I used some painter's masking tape, to tape artist's eraser putty over the tip of the arrow. The putty is formed around the tip of the arrow, and a roughly 6 inch metal bolt. Both the bolt and the eraser putty are taped to the tip of the arrow. The metal bolt serves two purposes: to slow the arrow down (it can go really high with a 50# bow), and also give the arrow more weight so that it falls through the tree limbs better (it hasn't gotten stuck yet!). The putty is for safety, so that when the arrow comes plummeting down, it doesn't damage whatever it hits quite so much. The notch that the string rests in also has a small hole drilled out, so that the fishing line can be threaded through it.
The basic idea behind hanging a dipole antenna is simple: hang a rope in a tree, on each side of the dipole. Attach the ends of the rope to the dipole, and then pull the dipole into the air by tugging on the rope. Now for the details.
I used 500 lb para-cord (available from E bay or Amazon) as the rope to hang the antenna, but this is far too heavy to launch into the air with a 50# bow. So first, I launched the arrow with fishing line attached, and then tied the fishing line to the para-cord. Then, I pulled the fishing line all the way over the limb, until the para-cord had both ends hanging to the ground, over the limb. At that point, you can then detach the fishing line. Be careful not to let the rope fall off the limb! I usually follow this step by immediately tying the ends of the para-cord together, so that it is a loop, and cannot fall off the tree limb. Note: any knot used (unless otherwise mentioned) is a bowline knot.
Now there is usually too much friction on the tree limb if you try to attach the antenna directly to this rope and pull it up. A pulley greatly helps this situation (see picture below)...
Not shown in the picture is a something similar to a figure-eight loop knot, through which the unscrewable metal link is attached. The metal link now attaches the pulley to the rope.
Next, tie another para-cord to the end of your dipole antenna, and thread that para-cord through the pulley. The idea here is to put the least amount of stress on the tree limb, and save the heavy lifting for the pulley. Keep the para-cord with the dipole attached slack, and then pull the loop of rope around the tree limb until the pulley is as high as you want the antenna to be hung. Go to the other tree limb, repeat. Now, the para-cord with the dipole attached on each end should be long enough that the dipole is lying on the ground, or is very loose. This puts the least amount of stress on the tree limbs. Now, the fun part. Pull the ends of the para-cord that is threaded through the pulley, so that the dipole is now hanging in the air. Pull it as tight as you can get it, but be careful not to break the tree limb. One end of the antenna should be tied to something so that it cannot come undone. On the other end of the antenna, it is highly recommended to tighten it by hanging something heavy, like a couple of bricks, on the rope. This way if it is windy, and the trees start moving around, the antenna (and tree limb) will have some stress relief, as the brick tied to the other end of the antenna let's the rope move up and down. Of course, the dipole might not be quite as flat-topped as desired, but it should make for a more robust installation.
That's it for now. Please feel free to question/comment on this installation procedure. Good luck!