Time for just a short note -
I have used nothing but copperweld for antenna wire for 40 years, never
had a span fail due to corrosion, or for that matter, for any other
reason. And, I have always lived in coastal communities. I normally
use #12 AWG wire for antennas, #16 AWG for things like open wire feeders
(I make my own lines). I agree that there are different quality levels
for this wire. The brand I use is Crown Metals, and it has never let me
down. As a side note, when I worked for the phone company up this way,
we had some open wire spans for telephone service (both direct and
carrier). These spans survived harsh Alaskan winters for more than 50
years. They normally used #10 AWG for "regular" spans of up to 250 feet
between poles, and #8 AWG for long spans, up to 500 feet. Crown metals
brand products are available from AES, the last time I looked, and
probably from most of the other vendors of antenna parts you see in QST.
Yes, copper clad wire gets an outer layer of copper oxide, but there
seems to be no degradation of performance. I dislike insulated wire
because water can creep inside the insulation, and that can be bad news
for any antenna. Using house wire is not a good idea, as it is not
very strong for its weight, and it is carrying the added load of plastic
insulation. Stretching regular wire about 10% will harden it
considerably, but this only approximates "real" hard drawn wire - which
does not stretch appreciably.
Also, there is no rule that says you have to use copper. Aluminum
electric fence wire works well, but you have to remember to use an
anti-corrosive coating at the joints. A typical product is "Noalox".
Fence wire is light weight, inexpensive, and quite strong per unit of
length.
Try to find 14 or even 12 gauge if you can, but smaller sized work for
most uses. Larger diameters are better both from a strength perspective
and have less ohmic losses. However, in a pinch, any size is better
than none. For low power work, I often use 24 gauge magnet wire for
temporary antennas, and it always performs well electrically, even if it
has trouble surviving storms.
Here's a hint for making your own open wire feeders: For spreaders, I
use a plastic material sometimes called "UHMW" (stands for Ultra High
Molecular Weight, I am told). This is a black UV stabilized material
that is nearly indestructible. I get it in 1/2" thickness, and use my
standard wood bandsaw to cut it into strips about 1/2" square by 5"
long. Drill a couple of 1/8" holes about 1/2" in from each end, and
attach the insulators to your feedline with tie wires, spacing then no
closer than 3 or 4 feet. 25 of these spreader insulator thus make a 100
foot open wire feeder. Use #16 AWG copperweld for the feeders, #18 for
the tie wires. Solder each tie wire to the main feeder wire. BTW - the
tie wires go through the holes, not the feeders I have had such a
feeder up for 30 years, and it has never failed. It will also take any
(legal) level of power you care to use. There is no significant heating
or other distress at 1500 watts CW, even when working with high VSWR
(8:1 mismatch or more), and in rain or snow. The plastic can often be
obtained from your local vendor of plastic products as "cutoffs" for
significantly reduced prices. The material is commonly used for sled
runners, boat fenders, dock fenders, and so on. UHMW is also suitable
for end insulators, Cut a length about 8" to 10" long by 1" wide (from
the same 1/2" thick material), drill a 1/4" hole about 1" in from each
end, and you're good to go. Such an insulator held a 700 lb test load
without difficulty. It might have held more, but the wire I was using
to support the weights broke.
Good luck, and 73
Jim, KL7CC
[EMAIL PROTECTED] wrote:
In a message dated 9/8/2004 5:40:06 AM Eastern Daylight Time, Charles Greene
<[EMAIL PROTECTED]> writes:
If you live near enough sea water to get an >occasional sea spray, the
copperweld copper clAdding will corrode green, >then the core will rust in
several places. After that the wire breaks if >flexed like.
It doesn't require salt spray to do that, either. Just takes longer.
What happens is that *any* break in the copper cladding can let in moisture,
and set up an electrolytic corrosion situation. The steel core corrodes like
mad because it's essentially the cathode in a copper-steel cell whose plates
are shorted. Of course salt water makes a better electrolyte than rain water,
but any sort of ions in the water help things along.
Pretty soon you have a piece of copper tubing and the wire fails.
There are different levels of copper cladding, too - some are much thicker than others. There are also versions with insulation, which tends to protect the wire everywhere except joints. Joints can be protected by Plumbers Goop or similar noncorrosive sealer.
Some folks swear by copperclad, others swear at it, but it *is* the strongest
stuff for a given gauge.
In the end, a lot depends on your replacement philosophy. Some folks replace
before it falls down, others after...
73 de Jim, N2EY
I didn't used to believe all the stuff about acid rain and UV exposure until I
saw what my wire antenna hardware looked like after 5 years aloft. Not pretty!
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