Topband: ALUMINUM

[N2TK, Tony]

I had aluminum covered hardline in upstate NY. Where it was on top of the
grass, ground, leaves, pine needles it was fine. Where it went underground
for about 25 feet the aluminum turned to goo after 4-5 years.

73,
N2TK, Tony 

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Tom W8JI
Sent: Saturday, March 09, 2013 12:49 PM
To: Topband at contesting.com
Subject: Re: Topband: ALUMINUM

I use CATV hardline everywhere here and have had some left over bare coils
on the ground for the 24 years Ive been here. Except for staining from
leaves, etc it is still fine appearing. The ground is mostly leaves, twigs
and pine needles. The bare cable CATV runs in this town have been up even
longer and Ive been told by installers the operational life is expected to
be 25 years or longer, unless it is subject to physical damage of course
which is SOP from storms.>>>>>

This topic, because there are so many variables that affect results, is like
the never ending radial bantering. There isn't one answer.

There is a huge difference between aluminum just sitting on the ground in
coils or laying on dry ground and aluminum connected to things that apply a
"battery" voltage or have moist soil contact with dissimilar metals.

Aluminum has a threshold where, if potential is below a certain level, it
rapidly builds a protective insulating coating and stops eroding. If it gets
above that level, especially in the presence of chlorides, it will erode
endlessly until it is gone.

There also is a huge difference between CATV cables suspended from rigid
messenger lines and wires that constantly flex (like thin wire) or vibrate.

Aluminum work hardens and cracks. That's why, on occasion, a #9 aluminum
fence wire element for my 160 four square will just break and drop. They do
this even though they are under no real stress at all, just hanging there
from catenaries lines. They also break on occasion at flex points. Not too
often, just one once a year or so.

Like radials, some systems make people happy and some do not. The #9
aluminum fence wire is worth the occasional breaks in my 4-square elements
because it is cheap to replace, light, thick, and does not weigh the lines
down.

73 Tom 

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Topband Reflector