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how to hang a dipole

Discussion in 'General Technical Questions and Answers' started by K7MHI, Jul 30, 2009.

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  1. K7MHI

    K7MHI XML Subscriber QRZ Page

    so I am having trouble figuring the best way to deal with getting a dipole up in some trees I currently have some trees in my back yard that are about80-100 ft tall. The Trees are on either corner of my back yard and I can string a 80m Grv5 or Off center fed dipole My house is about 14ft from one tree.

    The problem is how do I deal with the ladder line/feed line?

    My current install plan is to rent a genie hoist because I also need to trim up and fell a tree as well as some other high up work, so while I have this unit I will also put some big 2" eye hooks in the tree as high as I can get on the lift. I will then string up the dipole and put the line to the ground, this way I can weight the line and it can move in the eyehook for wind/tree movement with out ripping my antenna, as well as give the ability to repair antenna if needed by dropping the line.

    but the issue I am not sure about is if I have a end supported dipole 100ft in the air, with a ladder line dangling from the middle of it (the black dot) then cross over to the trunk of the tree with the coax feed will this stress the antenna too much?

    how do you deal with this or how would you suggest to put up an antenna in this situation?

    I should also add that right in the middle of the two trees almost equaldistant I have another tree about 50ft High that I currently plan to fell (unless its a awesome antenna rig tree) I didnt put this tree in the graphic


    [​IMG]

    if the image wont show up... http://www.kellykeeton.com/x/antenna.jpg
     
    Last edited: Jul 30, 2009
  2. W9GB

    W9GB Ham Member QRZ Page

    Why not a pulley on that eye hook?
    Then just like a sail boat ... you can change "sails" (your antenna).

    w9gb
     
  3. KA4DPO

    KA4DPO Premium Subscriber QRZ Page

    There's an old saying about antennas that say's " If you put it up and it stays up it wasn't high enough, if you put it up and it comes down it wasn't strong enough".

    I would also go with the pulley and eye hook, makes replacing them a lot easier.
     
  4. KD0HFZ

    KD0HFZ Ham Member QRZ Page

    Yes, a pulley is a great idea. Put some weights on the end, and then when the trees sway, the dipole wont be snapped, and you can change antennas faster.
     
  5. AG3Y

    AG3Y Ham Member QRZ Page

    The pulley is almost a necessity. You would be surprised at how much friction can be generated by putting a rope directly through an eye-bolt!

    The ladder line, or some open wire feed line, should not stress your center insulator much at all. Either type of feed can be much lighter than coax cable, and if you intend to use the antenna on many different bands, your losses will be much less.

    I would bring the ladder line as close to the house as possible, and only use coax to go through the walls of the structure in order to minimize losses as much as possible. You can use a 1:1 current balun on the coax line to keep RF out of the shack although I have had success in just making a connection directly from coax to the ladder line ( ! ! ! ) and not experienced any RF problems. I know, maybe I am just lucky !

    Good luck, and let us know how things come out !

    73, Jim
     
  6. WA7PRC

    WA7PRC Premium Subscriber QRZ Page

    Hi Kelly,

    There are many ways to get an antenna into a tree. The bucket lift is but one. Use whatever works for you but I'd advise you to have someone on the ground to help (or call 911 if needed).

    Screwing anything into the tree is bad for the tree, could pull out, and is also a poor subsitute for a pulley. Better to loop a rope loosely around the tree, above a branch(es). A section of rubber hose will lessen the tendency of the rope to become embedded into the tree. Use rope that is UV-resistant. If you tie this rope to a pulley, you can then use the pulley to raise/lower the antenna. I use a nylon & stainless hardware closed pulley. Instead of tying the antenna rope off, use a counterweight near the bottom of the tree to maintain tension on the antenna wire. I used 5- and 10-lb dumbell weights. McMaster-Carr has a chart regarding the characteristics of various fibrous rope: (http://www.mcmaster.com/#about-fibrous-rope/=2xytdg). I use ΒΌ" double-braided nylon rope.

    There are some choices for antenna wire. Some like solid copper-coated steel, aka CopperWeld(TM). Others prefer hard-drawn stranded copper wire. I use 12ga 259 strand "Flexweave" wire from Davis RF (http://www.davisrf.com/) for long single-wire antennas. My 4-wire 80m cage inverted vee uses 14ga Flexweave. They also have a fine selection of insulators & feedlines. My antennas are all coax-fed, so I can't make suggestions regarding ladder line.

    73,
    Bryan WA7PRC
     
  7. W9GB

    W9GB Ham Member QRZ Page

    You can also use the counterweights (cast or pot metal) from old sash windows!
    I took 4 window weights from my parent's old house (free) -- when they were replacing windows several years ago. I cleaned and primed them to prevent further oxidation -- and they are in my "antennas to go" box!

    w9gb
     
  8. K7MHI

    K7MHI XML Subscriber QRZ Page

    thanks for the tips, yes I like the idea of a strap around the tree I might ponder that a bit.

    Its good to have the advice on the ladder line and stress that was my primary concern with this setup I didnt want the weight bogging down the antenna so much it causes problems. I will likely run the ladder as close to the house.


    Thanks for the advice guys!
     
  9. WA1ZPD

    WA1ZPD Guest

    Hmmmm, those are some awful skinny trees you have there. LOL :D







    Good luck with the antennas
     
  10. W4HAY

    W4HAY Ham Member QRZ Page

    I've been using large eyebolts into trees for over 50 years with good results. Last time I visited my hometown, a tree in which I installed one in '53 was still very healthy.

    The tree will eventually grow around the eyebolt, so you'll have to back it out occasionally if you don't leave enough of the shank exposed.

    I run and endless loop of line from the eyebolt/pully down to two large hooks about head-high which I use to secure the loop. The ends of the line are tied together with bowline knots, and the antenna secured at the same point. Either leave enough slack, or use counter weights, to prevent tree movement from parting the antenna.

    Cement in an old paint can with an eyebolt down the center makes a cheap counter weight.
     
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