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Tree-Mounted Antennas

Discussion in 'General Technical Questions and Answers' started by KI6CSJ, Sep 3, 2006.

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  1. KI6CSJ

    KI6CSJ Ham Member

    MY QUESTION - Does anyone make a time-proven mount and mast that will allow me to mount the mast to the upper most trunk of a tree and not kill the tree?

    MY CONCEPT - I'm hoping the tree trunk will disguise my mast enough that I can get decent height without an "ugly" metal tower.  I can get the first 25-30 feet of height using a tree trunk and have it support a mast that gets me another 20 feet or more.  The tree trunk is aesthetically pleasing and that way the mast will be less noticeable at ground level. The wife says this approach is okay with her, and that's always good to hear.

    The mast will be used to support a dipole or hang an inverted vee or possibly support a vertical & radials and/or J-pole or whatever.

    Any comments on the viability of this approach would also be welcome.

    Thanks to all.
     
  2. KA0GKT

    KA0GKT Ham Member

    This may seem to be an odd question but, what kind of tree? One of the problems with tree mounts is that either the tree grows around the mount or the mount straddles and strangles the tree.

    Tree mounts should be removed and remounted every year to prevent damaging the tree; if a tree is used to support a wire antenna, some kind of counterbalance or bungee-cord tensioner is needed to keep the wire antenna from breaking when the tree moves with the wind.



    73 DE KAØGKT/7

    --Steve
     
  3. AD7N

    AD7N Ham Member

    Even though it isn't part of the original question, but here is my question: for an "average' sized 2nd growth tree (say 1.5-3 feet in diameter cedar/pine/fir), what is the highest frequency you can go without getting a directional tree antenna? I.E. without the tree blocking signals from behind the antenna?
     
  4. K9KJM

    K9KJM Ham Member

    I have helped a pro install antennas in trees for many years.   The tree of choice around here is the white pine.
    Climb the tree with climbers gaffs up to where the tree trunk narrows to about 4 inches or so, Cut off the top of the tree, Drill two holes about 3 feet above/below each other and bolt a mast thru them with 3/8" diameter, long bolts or threaded rod with washers.  
    We have done this for both large television antennas and vertical FM gain type antennas (And in the '70's for CB antennas).
    Be sure to run a nice heavy wire from the mast to ground rods at the base for lightning.
    It is rough to somehow attach the coax coming down the tree, As the tree keeps growing around any staples......  The best method seems to be to just attach the coax at the mast with a "messenger" wire that is also attached near the bottom.
    Some of these installations have been up for over 30 years now, And do not kill the tree.........
    Unless there is a lone tree in a yard, It is very difficult to see the antenna that was installed this way........ [​IMG]
     
  5. KI6CSJ

    KI6CSJ Ham Member

    I have a choice of only a very few trees, two really. Both are in my back yard.

    There is a mature Chinese elm that's at ground level and stands about 25' to 30' high at the very top. The canopy is as wide or wider than the tree is high. I think this is not the tree to use as elm grows in a very irregular shape with few straight, upwards-pointing branches. Elm is strong but the shape is wrong.

    I also have a healthy, actively-growing juvenile ash tree. This tree has a relatively straight trunk. It is about 20' tall but it is half way up the slope in my back yard, its top is actually higher than the top of the elm. It is not centered on the property so the length of the antennas "arms" may be limited by the shorter of the two diagonals to the property's corners. Ash is strong.

    I would hesitate to bolt through the tree, preferring to wrap the mount around the tree - even if this means annual movement of the mount. If the mount wraps around the tree I would want it to be a flexible mount that gives the tree room to grow.

    I've seen trees with bolts through them.

    The consequences of losing either tree could not be remedied in my lifetime. The elm tree, to some extent, is why I agreed to buyy this house.

    Hmm,... how about a ground-mounted tower that is hidden by the tree - one which cannot be readily seen from the house?
     
  6. N0XAS

    N0XAS Ham Member

    I had a length of galvanized fence top rail run up alongside the trunk of a crabapple tree at our old house. I used dacron line to loosely secure it to the trunk in 3-4 places, allowing for some movement but not a lot. Used it for my VHF antenna, but I could probably have used it for a dipole support as well, maybe even a small beam or vertical. It was almost invisible when the tree had leaves, and the canopy hid the antenna from view from anywhere in our yard.
     
  7. WB2WIK

    WB2WIK Premium Subscriber

    I guess you didn't know you can plant a 25' elm tree anywhere for about $1500?

    My XYL and I have planted mature trees hundreds of times. Including a pair of 45' tall date palms that weighed more than two tons each. About $3000 is all it took to get it done, and they were in a day later.

    I can't imagine basing a house buying decision on an elm tree, but then again...

    If you have a tree partway up a hill in the yard, rather than attaching anything to the tree itself, why not just use the tree to hide a permanent antenna mast installed in a concrete foundation "behind" the tree? You could make it look just like the mast was supported by the tree (nobody looking from a distance would know the difference), but the real difference is you wouldn't be potentially harming the tree, and you'd have a more permanent installation.

    An antenna mast strapped or bolted to a tree would never pass a building and safety inspection, but one installed in a concrete foundation engineered to support an antenna mast would.

    WB2WIK/6
     
  8. K9KJM

    K9KJM Ham Member

    Anything wrapped AROUND a tree trunk will kill it.
    Bolting THROUGH the trunk will not.
    Talk to the pros who repair trees damaged in wind.......
    I suspect you are correct that Elm trees are the wrong choice to consider mounting a mast in........ [​IMG]
     
  9. K7FE

    K7FE QRZ Lifetime Member #1

    NEVER wrap wires or rope around branches, after a couple years growth, it will choke the limb and it will fall off in the wind. Always use large wood screws and allow for trunk growth by not turning it all of the way in. I have used 1/2 inch wood screws and left three or four inches of screw length sticking out to attach a mast to with U-bolts. In my case, one inch diameter TV mast 20 feet long in a 50 foot pine tree holding a 40 meter inverted V. Trees are your friend and are great to hold up WIRE antennas.

    If you have a Yagi in mind, plant a steel tower.

    73,
    Terry, K7FE
     
  10. G8ADD

    G8ADD Ham Member

    I have joined together two 2" steel scaffold poles and have them going up though an upright Sycamore tree from a buried concrete base at the foot of the tree. It took a bit of judicious removal of branches to get a clear path to swing the poles to the vertical position and get a clear route for the antenna. Now this is the part that you might find useful. I planted a couple of clematis and trained them up the pole. One is a clematis montana which is capable of getting to the top of any tree likely to be found in a normal garden but which becomes bare at the base after a few years, and the other is a lower growing evergreen hybrid (which I have forgotten the name of) which decently clothes the bottom of the pole in foliage. These clematis plants not only disguise the pole, but in season make an outstanding garden feature in their own right and need no maintenance!
    There are other plants which will work as well, such as an ornamental ivy, so you can adapt this stratagem to the taste of your XYL, but I would recommend painting the poles so that they do not attract attention with bright reflections! (And of course, they are NOT antenna poles, they are plant supports!)

    73

    Brian G8ADD
     
  11. KC7JTY

    KC7JTY Banned

    I built a tree top mount using 4 lengths of 1 1/2" angle & 8 pieces of (approx 1 1/4" dia.) steel pipe 1 1/2" long. The angle lengths are longer than the diameter of the tree to accept threaded stock through holes drilled on each end for clamping the 2 brackets together. The pipe pieces are welded onto the angle's flat surface so they will be vertical and parallel with the tree trunk when installed. When properly made the 4 pieces of pipe will be the only contact with the tree trunk. They should contact the trunk at 90 degree spacing.

    Space the mounts about 3 feet apart and connect a length of EMT tube which will receive your slightly smaller dia mast which will be telescoped into the 3 foot tube bolted to the mounts.

    This will allow the tree to grow into the air space between the pipe & angle. It worked quite well for me.



    Top the (single trunk) tree first
     
  12. KA0GKT

    KA0GKT Ham Member

    If you plan to use a wire antenna on your Chinese Elm, I suggest that you use something similar to this to keep your wire tensioned:
     
  13. M0DSZ

    M0DSZ Ham Member

    Try a tanalised (treated) wooden pole about 2" diameter and as long as you need . A couple of wood screws should stop it turning and the rest of it is secured with those PVC straps sold to anchor juvenile trees to support posts. My "tree" is a Norway spruce (Christmas tree) next to the shack, it does sway in the wind but there's a good length attached to the tree.

    Cheers,

    Hugh
     
  14. KI6CSJ

    KI6CSJ Ham Member

    Many thanks to all.  You've given me some great ideas of the type I was after.  I don't forsee starting out with a full-blown antenna tower, whether concealed or not.  It's too big of a commitment when getting started.  A temporary pole support for a wire antenna will have to suffice for now.  

    Painting the pole is a great way to camouflage it that I had been thinking of.  I hadn't thought of rigging it with tensioners but it makes good sense and won't cost too much, either.

    What wire does one use for this that can handle being under tension without creeping, fraying, etc. What is the best UV-resistant insulation to get, or do you use bare wire?

    Scaffolding poles as the upright sounds really good to me - stout, modular, corrosion resistant aluminum,...

    Any other ideas on this would be greatly appreciated, even if it's just a variation on a theme.
     
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