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1-5 of 5 messages
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"Poles" for dipole?
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by K3ASA on November 2, 2005
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Well, the shack is complete.. Now I need to get my antenna up. No trees here which would be workable, so I need a couple poles. I called the power company (and an electric contractor..) and they said 30' poles, with 5' buried/25' in the air would cost in the neighborhood of $500/each! Yikes!! I want to install the 75' dipole with the feedpoint at the top eave of my 2 story house, and then the legs out to a couple poles... everything about 20' up. (kind of a horizontal sloper...) Any suggestions for a cheaper pole?? I hate to spend $1000 to get a couple poles in the air! (Maybe PVC, but that stuff will bend too much at 20' up, wont it?? With the petroleum problems, PVC is probably higher than Wood poles now.. ) Comments appreciated! 73.... Gene
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RE: "Poles" for dipole?
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by WB2WIK on November 2, 2005
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Utility poles really are expensive. I'm surprised you were quoted only $500 each, I would have guessed higher mostly due to the labor and transportation costs involved in delivering them.
But utility poles are severe overkill to support a wire antenna.
I don't know what kind of "75 foot dipole" you have (that's an odd length), but if you intend to use it on the lower bands, e.g., 80m and 40m, having a vee dipole as you describe up only 20' above ground is going to be pretty disappointing. It's an okay height for 6m or 10m, but for lower frequencies 20' is almost like laying it on the ground.
I'd consider installing it like this:
-Roof tower with extension mast, installed at peak of roof. If you use a Glen-Martin 8' 4-legged aluminum roof tower (light, cheap and very strong) with a 20' mast installed in it (3' inside the tower, 17' outside the tower) and your house is 20' high to begin with, now you have a mast up 45' above the ground.
-Install mast with permanently mounted pulley at the top of the upper mast, with a rope through the pulley so you can conveniently raise and lower wire antennas to your heart's content while standing on the roof, or possibly even standing on the ground if you arrange it well.
-Install wire antenna as an inverted vee with feedpoint at 45 feet and ends tied off lower, using leader ropes to the roof edges or any other support you can arrange. This way, the ends of the dipole only weigh a few pounds and they can be supported by almost anything. All the real weight is at the center, up on the pole.
This would cost much less than a single utility pole and gets the antenna up at a much more usable height.
WB2WIK/6
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RE: "Poles" for dipole?
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by WB6BYU on November 2, 2005
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TV pushup masts work fine for wire antennas and are much
cheaper than the utility poles you inquired about.
Galvanized water pipe is sold in 21' lengths.
See what lengths of 2x2 or 2x4 boards you local lumberyard
carries. A 2x4 board ripped in half lengthwise gives
you two masts. And you can splice them together if needed.
There are other designs for wooden masts up to 40' in the
ARRL handbook/antenna book (at least they were in the
older ones.)
PVC or ABS pipe has been used up to 40', but you need a
relatively large diameter and some guy ropes. (I had a
20' ABS mast on the house with one set of guy ropes and it
really needed two sets to keep it from bending in the
middle.)
Whatever you put up, attach a cross-bar and two pulleys
on the top before you mount it. This makes it much
easier to lower the antenna for tuning and maintenance,
and allows for additional antennas in the future.
If you can support the weight of the feedline on a mast
(rather than having it hang in the middle of the antenna)
then the end supports can be much lighter.
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RE: "Poles" for dipole?
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by KA0GKT on November 8, 2005
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Find a copy of the tenth edition (or earlier) of the ARRL Antenna Book. There are several wooden antenna support plans which would be suitable for your antenna.
The tenth edition has a blue cover. The eleventh and twelfth editions have brown covers.
73 DE KAØGKT/7
--Steve
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RE: "Poles" for dipole?
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by N7DM on November 21, 2005
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Like BYU says, PVC works well, but requires guying. I have two 60 footers. Likewise, during this part of the Cycle, when my favorite bands of 12 and 17 meters are pretty much 'done', I use a dipole.. around 80 feet over-all, with tuned feeders, to work 17 [when I can] down through 80... It works... as well as the crummy propagation here will allow, anyway.
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