Installing a dipole thru a tree...help
I want to get a G5RV antenna and string it between two trees. The length is 102 feet. However there will be about 10 feet at each end within the trees themselves. What can I do to insulate the antenna itself from contact with the tree? Is that really necessary? Here is a diagram.....
Keep in mind that I want to eventually run full power thru that wire, or at least as much as that antenna can stand.
Any advise on this installation?
Hams run transmitting antennas through trees all the time.
Worst that can happen is you start a fire in the tree. I've actually seen that happen, twice. However it's pretty rare.
To help avoid this:
-Use only well insulated antenna wire
-Use high quality ceramic or glass end insulators
-Where the wire "ends" (terminates at each end insulator), screw an electrician's wire nut tightly over the end of the wire, so the copper is not exposed -- or do something similar to insulate each wire end
-Use good rope at the ends of the antenna, after each insulator
It's about all you can do.
The only times I've seen a fire start was when the end (or near the end) of the antenna wire made contact with fairly dry leaves or tree branches.
I run my end-fed wire antenna over the branches, through the foliage, and down the other side all the time. That may sound like a pretty sloppy and un-ambitious way of doing an antenna installation, but I'm having to do it in a different location every month or two all year long. (Campground hosting for the parks department of Oregon.) I use great wire which I purchased from The Wireman, which is 40% copper clad #18 steel stranded with a VERY durable and effective insulation on it. I routinely operate with a thousand watts on sideband - primarily on 75, 40, and 20 meters. Not one little spark or arc yet.
The only time I have ever had a problem with high-voltage arcing on an antenna wire was once when I had strung up a coax-fed shortened 75M dipole which contained two loading coils in the center of the legs. I had a piece of 3/4' PVC pipe fashioned into crude insulators on each end, and the ends were supported by some strong but thin kite line. (Again... temp. antenna). It was wet, and I shot the thing with high power and caused an arc across one of the end insulators and the whole thing fell down on top of my motorhome with a big CLUNK. I think I remember having a 4:1 balun up there also (my stupid method of transforming from coax to the antenna wires.) So arcing can happen, and I suppose in most likely places like the ends.
My end-fed inverted L and U antennas work so well and are so much easier to put up these days, that I'm quite sure I'll not be trying that kind of dipole thing again... but you should be doing what you think is right for you. If you want to see some of the things I've been doing (just for casual entertainment) go to my website and http://k7zrz.net and click on the amateur radio link. Good luck with it all.
That's a common problem when you combine wet weather with lousy insulators. Use ceramic (porcelain) or glass insulators and this is extremely unlikely to ever happen again.
Originally Posted by K7ZRZ
I am the world's expert at putting dipoles through trees.
Unless you're running so much power that you're in danger of lighting your trees, it is unlikely you will notice any difference in performance of your antenna as opposed to it being in the clear. You might want to consider some sort of strain relief if your trees flap in the breeze a lot, but that's about the only thing you need to worry about.
Except for moose, maybe.
"The more you know, the less you don't know."
I hope you don't think I didn't learn my lesson on that the first time....
Originally Posted by WB2WIK
Im just worried about losing signal or shorting out the antenna against the tree especially in wet weather and if that will cause any kind of problem with my radio.
I know to use good insulators at the ends of the wires but what stops the wire itself from shorting out against a limb or leaves since the wire goes thru the tree?
Also, can I run 1500 watts thru a wire that runs thru a tree?
Or do I need to use completely insulated wire? And if so, what is good? Does the insulation cause any rf problems?
Im pretty rookie at this.
USE INSULATED WIRE!! Otherwise, yes, your antennas would be shorting out against the trees.
The insulation will shift the Velocity Factor a bit, but you were going to fiddle with the length anyway, weren't you?
Yes, that was stressed in my first post reply to you: INSULATED WIRE!
Originally Posted by KI5VY
Stranded insulated wire is much easier to work with than "solid" (single conductor) wire, and there's a lot on the market that is made exactly for this application.
A good example is wire type FW12P listed here: http://www.davisrf.com/antenna-wire/flexweave.php
When I built my junk box 811aX4 amp I was using a bare wire dipole on 80M.
I was in a QSO when my XYL came running down the stairs to my shack yelling "Our tree is on fire !!!!". I went out and saw a burned spot where one end of my dipole was brushing against a tree branch and some embers and ash fell onto the front lawn.
Now I make my dipoles out of #14 insulated , stranded THNN wire.
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