how much to stretch copper wire

[Jim Hoge-2]

I drew the wire for my first antenna about 40 years ago. That was for a quad utilizing solid copper. Since then,I have made numerous dipoles, all using stranded THHN or THWN 12g wire. My method has always been to anchor one end to a tree or a bumper hitch and hold the free end with a pair of Vise grip pliers. The advantage of the armstrong method is you can feel the draw and sense when it nears its limit. The force require to continue drawing the wire escalates and then failure occurs. In practice, I lay out a tape measure on the ground beneath the wire to be drawn. Once I have my rough length of wire, I will draw it about 10% more in length. (Example: 1/4wave for 7.010 mHz is 33.3' so I will draw to about 36.7'.)This has been enough to prevent additional stretching once the antenna is up in the air. The thermoplastic insulation degrades well before the wire fails and my oldest antenna up at the moment is my 40m dipole, it's about 12 years old.
73,Jim W5QM

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[Charlie T, K3ICH]

Or, you could simply use copperweld and forget
about stretching.
RF Connection sells a fairly flexible stranded and
insulated (black poly-ethelyne) wire that, if I
remember correctly is 13 gauge.

I built a four band dipole * a few years ago using
those aluminum swaged wire clamps.  It's still up
and to my knowledge, has not stretched or
de-tuned.

73, Charlie k3ICH

* Two wires from each center balun connector.  The
upper wires have 75 M traps for 75/160M and the
lower wires have 40 M traps for 40/60 M bands.



-----Original Message-----
From: Elecraft
[mailto:[hidden email]] On
Behalf Of Jim Hoge
Sent: Thursday, February 11, 2016 5:58 PM
To: Elecraft Reflector <[hidden email]>
Subject: [Elecraft] how much to stretch copper
wire

I drew the wire for my first antenna about 40
years ago. That was for a quad utilizing solid
copper. Since then,I have made numerous dipoles,
all using stranded THHN or THWN 12g wire. My
method has always been to anchor one end to a tree
or a bumper hitch and hold the free end with a
pair of Vise grip pliers. The advantage of the
armstrong method is you can feel the draw and
sense when it nears its limit. The force require
to continue drawing the wire escalates and then
failure occurs. In practice, I lay out a tape
measure on the ground beneath the wire to be
drawn. Once I have my rough length of wire, I will
draw it about 10% more in length. (Example:
1/4wave for 7.010 mHz is 33.3' so I will draw to
about 36.7'.)This has been enough to prevent
additional stretching once the antenna is up in
the air. The thermoplastic insulation degrades
well before the wire fails and my oldest antenna
up at the moment is my 40m dipole, it's about 12
years old.
73,Jim W5QM


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[Bill-3]

Short runs - that being under 65 feet - I make with stranded #12 using a
PE UV-safe insulation. I used to use all kinds of the flavor of the week
of proper antenna wire. I have never had a 75 meter dipole using any
kind of #12 wire break from a weather induced load (ice/snow). I do not
use anything less than #12 on antennas.

If there is any stretch, I have not seen it - but, I also have an
antenna tuner. So, I might have never noticed.

My current primary NVIS for 75 has been in the air for nearly 20 years.
This summer it will be replaced with all new everything.

Bill W2BLC
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[Jim Brown-10]

On Thu,2/11/2016 4:48 PM, Bill wrote:
> If there is any stretch, I have not seen it

You don't see it unless there's significant tension on it. My 80/40 fan
dipoles are up 140 ft and are fed with RG11. The tensioning weight is
about 95#. I must trim it every 2-3 years.

73, Jim K9YC


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[Bill-3]

I should have mentioned in my earlier post that I use inverted vees
(picture a Maypole with fan dipole legs scattered around it) - which
means center supports holding up the feedline. That makes a light load
on the wires and much less stretching as opposed to supporting full
feedline weight with the antenna.

Bill W2BLC
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[Phil Kane-2]

On 2/11/2016 9:49 PM, Jim Brown wrote:

> You don't see it unless there's significant tension on it. My 80/40 fan
> dipoles are up 140 ft and are fed with RG11. The tensioning weight is
> about 95#. I must trim it every 2-3 years.

Does anyone use the strong-link / weak link system that is common in
shipboard wire antenna installations?  This prevents the antenna wire
breaking in the event of severe storms.

73 de K2ASP - Phil Kane
Elecraft K2/100   s/n 5402
Radiotelegraph Operator Cert. T2-00000208

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon
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[Jim Brown-10]

On Sat,2/13/2016 3:43 PM, Phil Kane wrote:
> Does anyone use the strong-link / weak link system that is common in
> shipboard wire antenna installations?  This prevents the antenna wire
> breaking in the event of severe storms.

Most of us with wires in trees use a weight and pulley system. Those who
don't will find them on the ground in the first good storm. Ask me how I
know! A few years after I moved here, I put up several wires and was one
weight short of having enough for all the antennas. I was going to do
that weight real soon, but real soon wasn't soon enough.

73, Jim K9YC
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