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Author Topic: Use of low voltage wire in dipole  (Read 9801 times)
AB8BC
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« on: September 17, 2011, 02:53:55 PM »

Anybody use the low voltage wire (14 guage) for dipole construction?  This is available at Lowes much cheaper than off the spool 14 gauge.  I'm sure there is a reason it's cheaper, but the question is, is it adequate?  I would use this as a single band, 80 meter dipole.  It would not be pulled tight and suspended by it's own ability.  It will be tucked near or in the siding on the house and supported throughout it's run.  This seems to be the best solution for me at this time....on the house.  I suppose I could lay it in the gutter, but I'm sure it would have some coupling issues

Regardless, has anyone used this before?  The wire I'm talking about is the kind you'd power the small, push in the soil sidewalk lamps.  I'm not sure who the manufacturer of the wire is.

Thank you for any input.  73.  Kirk. AB8BC
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DJ0IP
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« Reply #1 on: September 17, 2011, 11:58:41 PM »

Hi Kirk.  Looks like there aren't many takers.

I haven't any experience with that specific wire, but my experience with cheap wire is that the insulation often breaks down after a few years being outside.  In addition, pure copper wire cans stretch over time.

We're looking at 140' of wire here.
I would definitely go with the purpose-built stranded copperweld wire sold by the THE WIREMAN (www.wireman.com).

You can get 140' of CQ-532 (AWG 18) for $28,
or if you prefer thicker wire, CQ-531 (AWG 13) for $39.
Of course there is shipping cost on top of that, unless you pick it up at a hamfest.

You might save twenty bucks at Lowes, but you might also end up buying wire a second time.

GL es 73 - Rick, DJ0IP

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AA4PB
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« Reply #2 on: September 18, 2011, 04:56:09 AM »

The voltage rating of the insulation on the wire used in a suspended dipole doesn't matter because there is nothing close by for it to arc to. Copper wire used in electrical service however will stretch when tension is placed on it. That will cause the SWR to change over time. If you are using a tuner, the change may not matter to you.

I would highly recomment Copperweld for permanent antenna work. It is a copper plated steel core that is very strong and won't stretch. I find the solid Copperweld easier to work with because it doesn't want to coil up as bad as the stranded type. You have to be careful because even after stranded Copperweld has been up for years, when cut it will coil back up into a ball.

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Bob  AA4PB
Garrisonville, VA
K1CJS
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« Reply #3 on: September 18, 2011, 08:47:11 PM »

I wouldn't tuck that type wire into house siding, or even put it on top of it, since the insulation may break down under RF voltage.  On the same note, as AA4PB suggests, pure copper WILL stretch, and probably will contribute to the breakdown of the insulation even faster.

Bite the bullet and get the real thing.  You'll end up spending less in the long run--less in cash, and less in time needed to service that antenna.
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KF7CG
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« Reply #4 on: September 19, 2011, 10:40:42 AM »

I like to play with wire antennas. If an antenna stays up long enough to have significant stretch problems, it has been up too long. Insulation, what insulation, it isn't needed and just makes the lenth calculations more prone to error even if it shortens the antenna. For me, the best wire is the cheapest stuff that won't break while I am putting it up. Back when I could get junk TV sets with real transformers, I put up a lot of exeriments with #28 enamelled wire, has some up over a year.

For wire, whatever works; works.

Kf7CG
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KQ6Q
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« Reply #5 on: September 19, 2011, 12:35:39 PM »

AB8BC said he's going to tuck the wire into the siding on his house. Insulation does make a difference in this case, and with 100W or so of RF, there will be some points where the voltage is high enough to be of concern - arcing a bit, perhaps a fire hazard. I'd go with something rated for 110VAC, perhaps split some zipcord to double the length.
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KF7CG
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« Reply #6 on: September 20, 2011, 10:19:17 AM »

If his siding is like the siding on most of the newer homes it is PVC and will provide as good insulation as the PVC jackets on insulated wire. Most siding is also installed over a plasic foam thermal insulation that would make a good insulator.

Wood siding, the old aluminum siding, and some other things may not; normal vinyl siding is a winner.

KF7CG
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WB6BYU
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« Reply #7 on: September 20, 2011, 02:53:22 PM »

If your gutters are plastic there shouldn't be any coupling problems.  The SWR might change when the gutters
are full of water, however.

I use whatever sort of wire is cheap, usually spools of insulated, stranded hookup wire, sometimes magnet
wire, army field wire, or individual conductors spliced together from a short scrap of telephone cable.
Usually nothing bigger than #18, as it makes the antenna too heavy.

I've wrapped a number of wire antennas around a house, or tucked under the shingles, and have never
had one arc at 100 watts.  Not that it might not happen, especially if you try to use too short of an
antenna (which increases the voltages at the ends.)  The ends are generally going to be the worst point
for high voltage, so try to suspend the last several feet of the antenna wire away from metal flashing,
siding or trim.  If you have a particular problem point, slip some thicker insulation, heat shrink tubing,
plastic pipe or electric fence insulation tubes over the wire at that point.

I suspect that the wire you are looking at is similar to that sold for wiring sprinkler controllers.  I've got
some of that, and see no problems using it for antennas.  (But I've got single-strand stuff, so it isn't
worth my time to split it up and separate the strands.)  Yes, it will stretch overtime if you pull up too
much tension on it, but if you don't, it probably won't.  It is quite similar to the wire used for blasting
rock pits in Alaska - that worked just fine for a dipole, and had the added advantage that, if you
trimmed it too short, you could just pull on one end to make it longer.

I find that the PVC insulation on hookup wire lasts about 2 years in Western Oregon before it breaks
down in the sun.  Might only make it for one year in Arizona, depending on the exact composition of
the plastic.  (I'll have to check the wiring out in the greenhouse and see how it has survived - it
has been exposed to the sun for about 10 years now.)  If the insulation falls off, it will shift the
resonant frequency of your antenna slightly, and it might be a problem where the antenna runs
over some metal trim or flashing.

But in general there is no reason why you can't use such wire for antennas.
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AB8BC
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« Reply #8 on: September 21, 2011, 06:26:26 AM »

Thanks for the input everyone.  My gutters are aluminum, haven't really decided if want to try and load them yet.  But don't want to lay the wire inside because of the interaction with rain/snow piling inside.

I plan to use this antenna with around 600 to 800 watts behind it, so it wouldn't be QRP.  Time will tell if I would have RF in the house.  I've learn to just put it up and see what happens.  I have a working 80 dipole up now under the deck, that really shouldn't work as well as it does....but it does! 

Anyway, thank you all for your input.

73.  Kirk. AB8BC
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K1CJS
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« Reply #9 on: September 21, 2011, 11:09:00 AM »

If his siding is like the siding on most of the newer homes it is PVC and will provide as good insulation as the PVC jackets on insulated wire. Most siding is also installed over a plasic foam thermal insulation that would make a good insulator.

Wood siding, the old aluminum siding, and some other things may not; normal vinyl siding is a winner.

KF7CG

Back up a second and think.  If the siding were to stay dry all the time, I would agree.  But it won't--rainstorms do happen, and when they do, flashover to a house mounted conductive surface may occur--especially with the guy running 800 watts.  If you don't PLAN for the possibility of that happening, you're asking for a problem.
« Last Edit: September 21, 2011, 11:12:04 AM by K1CJS » Logged
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