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Author Topic: Antenna-Trimming Tree Limbs; Prep forSwaying Trees  (Read 647 times)
DALFOLLO
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Posts: 26




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« on: January 02, 2009, 03:17:09 PM »

Trimming Tree Limbs
--------------------
I am looking to build/install either a dipole or a G5RV, between two Spruce trees and a third regular tr I have on my property.

So far each leg will be about ~60', and the trees are about 40-50 apart. I understand having some length of the dipoles droop down is acceptable

- How important is it to trim back the branches where the wires will pass, so no wires rub on limbs? I am not looking to amputate the trees unless I really have to
- Wood itself is an insulator, however with tree sap and some water inherant with a live tree, I suspect there may be some issues

Preparing an Antenna for wind swaying the trees?
-----------------------------------------------

- I am looking to attach a dipole or G5RV to 3 trees (two are tall Spruce, and one regular tree ~30')
- Here in Colorado we can get some high winds, and I have seen the spruce sway 4-5' at the tops (near where I would attach the antenna)
- Any suggestions for building flexibility into the antenna's connections to the trees?
- I prefer setting up the antenna and leaving it there, if I can; Though I might be able to rig it such that it gets raised each time it is needed

Thanks for any feedback or suggestions.
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PHILIP_EX_KC7FWB
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Posts: 48




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« Reply #1 on: January 02, 2009, 03:57:00 PM »

No real suggestions about the first question. Really, the trees are too close together.

For the second part, the traditional answer, and one I have used successfully is to have the antenna tension line run over a pulley, then down towards the ground.

About 5' from the ground attach enough weight to tension the antenna.

As the tree(s) sway, the weight gets lifted up and down giving and taking up slack as required.
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N3OX
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« Reply #2 on: January 02, 2009, 04:03:37 PM »

"
- How important is it to trim back the branches where the wires will pass, so no wires rub on limbs? I am not looking to amputate the trees unless I really have to "

Use insulated wire and you don't need to worry.  I've used bare wire against trees without trouble, but if the high voltage points of the antenna rub against branches you might have SWR stability trouble and possible smoke/fire with high power, plus it could cause noise at least in theory.

"- Any suggestions for building flexibility into the antenna's connections to the trees? "

I used window sash weights on a rope through a pulley to provide strain relief on my whippiest tree supports.  That worked well.

Counterweights are good because they provide a constant pull no matter the displacement of the tree.  I've used garage door springs on some antennas too but they pull harder in stronger winds, so you need to be careful.

Some people use bungees but in my experience bungee rubber doesn't last too long outside compared to good rope, so if you decide to use something like that, I'd recommend having a couple of interlocking bowline loops in the rope or something that will "catch" the rope if the bungee breaks.  

Generally speaking , I recommend things like rope *loops* through the tree so you can haul the antenna endpoint *down* after the antenna breaks and use of the right rope for the job (I like black Dacron).  

"- I prefer setting up the antenna and leaving it there, if I can; Though I might be able to rig it such that it gets raised each time it is needed "

What you'll find with ham radio is that the time  the antenna is needed most even for hobby reasons is that cold winter night when some interesting DXPedition has gone to a place you want to work, or the day you can't leave the house because of snow.

If you become fond of DX and strange propagation conditions like me, too, you'll just hate having to drag your antenna up.  Every time I've ever had to set up an antenna before I could operate I would regret it, because I'd put it up and find nothing interesting DXwise and other times I'd have 10 minutes in between doing other stuff and knew some DX was on but didn't have time to put the antenna up *and* work it.  

I like to do some ham radio in between other stuff often.  Sure, I sit down for a long operating session, but I also don't read the newspaper with my cereal and coffee... I get on the radio.  

Having to haul your antenna up really cuts into that kind of operating, so do it right and it'll survive foul weather with minor maintenance.  I ran 6m (a very sporadic band) from an apartment with an antenna I had to set up every time because I wasn't "allowed to have it"

http://n3ox.net/projects/sixmoxon/

But I decided to just risk leaving it up a lot of the time in the summer to try to catch the tiny window of opening to EU that would sometimes come in the morning!

73
Dan


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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
K9WJL
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Posts: 183




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« Reply #3 on: January 02, 2009, 04:08:13 PM »

Another suggestion I have is to use bungee cords to tension the Antenna.
My 135' OCF dipole just survived 3/8" Radial Icing AND 35-50 MPH winds W/O problems, just using the bungees to hold tension.
73
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WV4L
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« Reply #4 on: January 02, 2009, 05:15:38 PM »

I haven't had any luck with the elastic stranded bungee cords they don't hold up to weathering. I've had much better luck with the black rubber type cords.
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WA2ONH
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Posts: 253




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« Reply #5 on: January 02, 2009, 06:53:45 PM »

Here's an article by K9LA on the affect of trees and low band antenna performance:

http://mysite.verizon.net/k9la/sitebuildercontent/sitebuilderfiles/low-band-antennas-and-trees.pdf
(3-page PDF file approx 30kb)

Good Luck & Happy New Year!

73 de WA2ONH Charlie
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73 de WA2ONH dit dit    ...Charlie
----------------------------------------------------------------------------
"No time is ever wasted that is spent LEARNING something!"
N5LRZ
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Posts: 0




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« Reply #6 on: January 03, 2009, 05:04:46 AM »

The cutting of limbs makes it easier to install wire anennas to be sure.  But before you do consult the internet or a tree surgeon as to the proper way to cut the limbs.  You would not want diseasees and fungus killing your antenna support.

As to the swaying.  Some peopule use elastic tie down cords at the ends.  I have even used old innertubes cut into strips being as I had an old tire around.

The old ARRL Handbook uses a pulley attached to the tree with a rope running thru it.  Attached to the rope at the bottom is a simple bucket with a hole in the bottom and some rocks to supply weight.  The water lets rain drain out.  The pulley allows the tree to move while still maintaining the same weight.  In todays world that bucket would probably be a salvaged 5 gallon plastic bucket from a painter with a hole drilled in the bottom filled with a required number of bricks.
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W4VR
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« Reply #7 on: January 03, 2009, 07:27:03 AM »

One end of my 80 meter dipole touches a pine tree branch..never had a problem...and I run a kilowatt.  My 160 meter 3/8-wave inverted L goes over the crotch of a tree at the 70-foot level...never had a problem with that one either.  I use insulated wire...the stuff you buy at home depot in 500-foot rolls.  I see no changes in SWR whether it's dry, wet, ice or snow!  Many years ago I had a 40 meter wire beam where one end of the director was touching a branch and I could see the flash-over at night...I was using bare wire on that one.
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WB6BYU
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« Reply #8 on: January 03, 2009, 08:58:26 AM »

I strongly recommend using complete loops of rope - like a flagpole
halyard - for raising your antenna.  That makes it much easier to lower
it for maintenance or repair - even when the wire is broken.  

A common problem with a single-rope approach is when the antenna
wire breaks and there is not enough weight on the end of the rope
to bring it back down to the ground.

Polyester (Dacron) rope is best for withstanding weathering over time.
The orange hay baling twine also holds up well, but suffers badly from
abraision when used in trees.

I use counterweights on at least one end of my antennas, and they just
survived half an inch of radial ice.  I envy Dan having sash weights -
they are my favorite, too, but are hard to find.  One of my wires is
anchored to a weight that sits on the ground - when the tree sways it
lifts the weight.  The other one goes to a chunk of metal pipe hanging
inside my tower where it can't swing and get tangled.  I don't trust
bungee cords to handle large amounts of sway without putting too
much tension on the antenna, but for temporary installations I  have
sometimes tied off the antenna rope to the end of a springy branch
to provide tension.
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N2UNL
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Posts: 15




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« Reply #9 on: January 04, 2009, 09:32:51 AM »

If I understand you correctly, you have a total of three trees ? If the space is far apart why not use three trees ? Inverted V works well. Even if you can only use 2 trees you can always achore the center of the V to the house. As far as the limbs go I would n't wory much with that if there not larg ones. I would use a counter weight system for the end of the ant. insulated with a rope to the wire. All i used fore a counter weight is a gallon jug filled with sand and for the pully i used a snap D ring tied to the tree.  Good luck and play safe in the trees.
              73's  Brian
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DALFOLLO
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Posts: 26




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« Reply #10 on: January 05, 2009, 03:36:19 PM »

All,

Thanks so much for your responces!

To clarify, I have three trees. I was planning to suspend the dirpole in the middle and then at the ends.

I suspect that I will have 5-10' of wire that is not 'flat'....meaning it dangle from the end support point. I have read elsewhere that having a few or several feet of the dipole dangle should be OK, as the majority of signal comes from the first 2/3rds of each side.
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