[TowerTalk] guage of wire for 500 watt antenna?
jc_ki7y at q.com
Tue Dec 5 13:04:36 EST 2017
I have seen in many years of working with wire that solid conductor can fracture and break a lot more often than stranded conductors. Especially if any kind of nick in the conductor when insulation was stripped off. And any constant motion will cause it to fail more often.
Most of my experience is with much smaller wire than #14 but think the properties would be the same.
----- Original Message -----
From: "Jim Brown" <jim at audiosystemsgroup.com>
To: towertalk at contesting.com
Sent: Tuesday, December 5, 2017 9:56:25 AM
Subject: Re: [TowerTalk] guage of wire for 500 watt antenna?
The NEC requirement is based on the need for physical strength, the
concern being that it does not break and land on power conductors. Which
seems silly -- you gotta be crazy to run an antenna above power conductors!
ALL copper stretches, stranded or solid. I have an 80M dipole at 120 ft
between trees fed with RG11, and it has about 100# on one end. It's #10
stranded THHN. Every few years I have to lower it and circumcise it to
correct for the stretch (1-2 ft on each end). For years, I've bought #8
bare copper from the big box store and stretched it to make it hard
drawn. We tie one end to a tree or telephone pole, the other to a
trailer hitch, and stretch it until it breaks. This wire, roughly 20-25%
longer, doesn't stretch much more once it's in the air. One of these
days I'll rebuild that dipole with it.
I don't know of any science that says solid is more robust than stranded
when subjected to repeated flexing or other stress. There IS a
reasonable concern that BARE stranded is more subject to corrosion, but
THHN insulation provides very good protection against that.
73, Jim K9YC
On 12/5/2017 8:36 AM, Alan NV8A wrote:
> I was quoting from a description of the NEC requirements rather than
> from the NEC itself, and you are correct: that description does not
> cover the situation where the antenna is exactly 150ft. long. Without
> checking, my guess is that the NEC in fact says "150ft. or longer."
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