On 9/17/2011 11:51 AM, Padraigh ProAmerica wrote:
Just acquired a couple reels of electric-fence wire from someone who got
smart and got rid of her horses. Question: is this wire (seems to be
aluminum) useful for antenna applications?

I have lots of electric fence wire that is aluminum. I like it because
it's easy to handle.

However, I have never tried it for antenna wire. It is quite soft and
stretches a lot. I suspect it would be fine for a 40 meter dipole, but
for anything lower in frequency it might continue to stretch under it's
own weight, plus a center insulator, balun and coax weight.

Try a length suspended at 5-6 foot and then add some weight in the
middle to simulate the coax and other stuff and measure the sag to
ground over a week or so time period.

Paul, KD7HB

Hi Paul,

Paul Drahn wrote in news:j54vrb$gaq$1@dont-
email.me:

....
I have lots of electric fence wire that is aluminum. I like it because
it's easy to handle.

However, I have never tried it for antenna wire. It is quite soft and
stretches a lot. I suspect it would be fine for a 40 meter dipole, but
for anything lower in frequency it might continue to stretch under it's
own weight, plus a center insulator, balun and coax weight.

That is an issue for annealed copper which is probably the most popular
conductor amongst hams, especially in small diameters.

One of the things that happens is that as the copper yields (stretches), it
work hardens, increasing its tensile strength. So, if the forces are not
too high, it might yeild a little, become a little thinner, a little
longer, a little stronger and survive (for now).

At some point, the increase in tensile strength of the copper does not
offset the reduction in cross section area and the stretch continues with
lower tension until it breaks.

Soft aluminium wire would not seem to comply with the NEC clauses for
antennas, though they are apparently widely ignored.

I collaborated on an antenna project where Gallagher XL HT steel cored 30%
aluminium clad wire (2.7mm overall) was chosen for long spans in a place
subject to high winds, snow and ice. It was well suited to the task, RF
conductivity similar to 2mm HDC IIRC, and much stronger.

Owen