[TowerTalk] Long Wire Sag

[Gedas]

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