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Re: [TowerTalk] Long Wire Sag

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Long Wire Sag
From: Gedas <w8bya@mchsi.com>
Date: Sun, 10 Mar 2019 15:32:36 -0400
List-post: <mailto:towertalk@contesting.com>
Hi Jim. Good hearing from you on this as I knew you had some long wires way up in the air. Funny you should mention pre-stretching as I was just considering that. I have never done so on purpose however.

In my mind I envisioned if I had a 300' length of say #12 and tried a pre-stretch that it would break near one of the ends and no where near the middle. Has that been your experience? I am thinking the middle of a long run is not as vulnerable to breaking. 73

Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 3/10/2019 3:23 PM, Jim Brown wrote:
I have a strong dislike for copperweld -- I find it miserable to work with, and neighbor W6GJB had a #12 copperweld 80M dipole break a few days after paying climbers almost $1K to rig it in his tall redwoods.

My wire antennas are at 140 ft between redwoods, and fed with RG11, rigged with pulleys, tied down at on end and a 90# jug of dry sand on the other.  I used to use THHN, #10 on permanent antennas, #14 for portable ones, but the #10 THHN stretches over time if under tension, and must be circumcised every few years.

If insulation is not needed, a far better approach is to buy a spool of #8 bare copper from the big box store and stretch it to approximate #9 hard drawn copper. WA6NMF introduced me to this idea around 2004, and neighbor W6GJB and I have done it several times since. We tie one end of about 200 ft of wire to an immovable object, like a tree or telephone pole, the other end to the trailer hitch of his pickup, and Glen drives very slowly until it breaks, while I observe at a distance.  The stretch is typically 15-20%.

73, Jim K9YC

On 3/10/2019 8:25 AM, Gedas wrote:
I am planning to put up a long inverted v antenna with it's feedpoint at 85' using 600' total wire (300' on each leg). The ends will be near the ground, only 20-25 feet high.

My question is given that each leg of this antenna will be 300' long am I better off going with a lighter weight #14 THHN insulated stranded wire or some heavier #12 THHN stranded? I am not going to purchase a different wire that would be better suited like copper-weld etc since I have plenty of these other two and want to try something today.

I realize there is going to be a _lot_ of sag in either case but I am not sure of the breaking strengths of either #12 or #14 and in the end which will help keep the wire up higher with less sag. Any ideas?

Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak. ilman/listinfo/towertalk
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