Copperweld wire

[KD0UN]

Not long ago, I came across a roll of number 12 copperweld wire -- about 200 pounds of it. I had a long wire about 5-6 hundred feet back on the farm.  My dad used quite a bit of it to build electric fences, but I still have about 100 pounds or more of it left, just waiting for that rhombic that I'm going to build.  Well, I say, not long ago.  I'm 65, and I bought this when I was fifteen.  Seems like just yesterday.  I've drug this all over the state of Missouri -- with no small amount of cursing.  Finally have three acres, and I might just get some of that stuff in the air.

[AA4PB]

I use #12 solid Copperweld. It doesn't kink as easily as the stranded version.

[N4NYY]

Quick question on the wire length. When figuring the length, you have to loop the ends around eye-bolts and egg-insulators and lose a few inches in the loops. Is the length considered the total wire length that is physically cut, or the total length after the loops are in place?

Sorry for the stupid question.

[WB6BYU]

It depends - where did you get the dimensions you are building it to?

If you are using the conventional 468/F formula, you have to understand that it is only
an approximation.  It will give you a starting point, but you still have to adjust the lengths
once the antenna is installed.

If you are using computer modeling to determine the expected lengths, then as long as
you can keep the wire looking like your model it should come out pretty close.  While
bending the wire around an insulator makes a fatter spot at the end of the wire, you'll
probably be close enough if the wire is soldered back to itself and you make sure that
the overall length of the antenna from the eye of one insulator to the other is what your
model suggests.

But if the wire is insulated, if the end of the wire is twisted around the standing part
without being soldered, or you didn't model it at the correct height above the proper
ground type, the resonant length may change.

I always cut my wires longer than expected and trim them for minimum SWR at the
desired frequency.  The easy way to do this is to install the insulator in a few feet
from the end, with the extra wire hanging down.  That makes it easy to trim off the
end of the wire without having to reattach  the insulator to the wire.  If you cut the
antenna too short to start with, solder a wire extension on at the insulator and do
your adjustments on that.

[W0OPW]

I asked a question a few weeks ago about copperweld ladder line and reported losses. It seems that all ladder line manufactured today is copperweld. I tried measuring the losses with my Autek antenna analyser and believe that the losses are much higher than claimed by the manufacturer. In essence, I get a u-shaped curve for losses due to the loss at low frequencies. The minimum loss appears to be around 10 MHz, then climbs up again. Is anyone keeping the manufacturers honest by measuring their feedlines?  If they reduce the thickness of the copper clad, there goes the efficiency.

[NA0AA]

Quick question on the wire length. When figuring the length, you have to loop the ends around eye-bolts and egg-insulators and lose a few inches in the loops. Is the length considered the total wire length that is physically cut, or the total length after the loops are in place?

Sorry for the stupid question.

Not really a stupid question.  In theory, it's supposed to be from end to end, right to the end of the loops of wire thru the insulators.  BUT, that 468/f is just a rough guess, and you will end up changing that to tune the antenna.

By the way, once you get the antenna tuned, it's useful to measure your final length so that you can incorporate a measure of reality into that 468 number - you might find that 452 or 477 might be a more accurate number for YOUR QTH. 

The note about the overlapping wire if using insulated - that's called Linear Loading, when the insulated wire is just twisted and not electrically connected.  It makes using insulated wire a minor hassle since once you cut the extra insulated wire off, you change the tuning!

[N4NYY]

Thanks for the answers. A couple things.

1. I am using this stranded polystealth, which appears to be stranded clad wire: http://www.davisrf.com/antenna-wire/polystealth.php

2. I am not using the 468/F formula, because I am using Unadilla traps. So they provided a formula to be used with their traps

Fo = Highest freq band
Fs = Lowest SWR for that band

Inboard leg, Initial length x (Fs/Fo) = new inboard length

Go to next band, calculate the change in length required, change + (234/Fo) x ((Fs-Fo) Fo) feet.

As I started to try and figure the correct numbers, I found another sheet that Unadilla sent me, and they have already calculated the numbers for you in a matrix. LOL. I hate it when that happens!

So, here is my one side of the dipole: 16' 6" (20M trap) 12" 3" (40M trap) 20' 3"

That last 20' 3" is for the SSB portion of 75/80M.

The antenna wire will be insulated, so I am wondering is I should cut them to actual length that include the overlap, instead of just cutting it for the actually physical size, determined by the formula.

[AA4PB]

Normally, the length should be measured to the hole in the insulator. Even if the insulation prevents you from making a DC electrical connection at the end of the loop-back, there be enough capacitance between the main wire and the loop end where it is wrapped around the main wire for physical support. That capacitance will make an "RF" connection at that point.

[WB6BYU]

The antenna wire will be insulated, so I am wondering is I should cut them to actual length that include the overlap, instead of just cutting it for the actually physical size, determined by the formula.

Neither.

Well, far be it for me to tell you what you should do, because doing things that don't work
as we expect them to is an important part of the learning process.  Either approach is just as good
in that respect...

Here are some of the quirks that make it difficult to predict the exact length of wire required:

(1) the insulation will shorten the resonant length of the wire somewhat, probably by a factor
between 1% and 5%.

(2) the formulas don't take into account the wire diameter, which affects the resonant length.

(3) the formulas don't account for the antenna height, ground type, or the angle between
the wires, all of which affect resonance as well.

(4) folding the wire back isn't the same as cutting it off, but it isn't the same as extending
it straight out, or letting it hang straight down, either.

(5) folding the wire back may be an effective way to tune the end of the outer wire, but it
isn't as practical for the inner section because you need to connect the wire to the trap.
With the wire folded back you either have to bend the end back around to reach the trap or
cut through the insulation at some point closer to the trap to make the connection.


My suggestion is to make the overall length of the center sections about a foot shorter on each
end than the formula would suggest.  (The formula uses 234/f to calculate each side, which is
the same as 468/f for the total length.)  Tie the wire to the insulator at this point leaving about
3 extra feet hanging down then looping back up to attach to the trap.  (This can be a piece
of regular stranded copper wire for flexibility)  That allows you to unsolder the end, trim off
some excess wire, and reattach the wire to the trap without having to untie the insulator. 
On the very ends of the antenna I'd cut the wires a couple feet long and attach the ropes 3' to
4' in from the end of the wire.  The end part can hang down and be trimmed for final SWR
adjustment.

[N4NYY]

I could definitely do that. I will just play it safe, cut them long, and trim from there. I can only get it up 35' at the apex.

[W4VR]

whichever gauge you decide upon, make sure it has a jacket covering the wire...believe me it will be worth the extra expense, if any.  I use open wire line made with copperweld and it's great stuff.  For my antennas I generally use 10 gauge stranded copper with jacket.

[N4NYY]

It does have a jacket.

[N3QE]

OK. After digging, the Poly-stealth is the stranded version. It appears I will use this. It is 13 gauge.

I succesfully managed a 130 foot span of 13 gauge stranded poly-stealth. It is not nearly as coily as the solid stuff (which I swear, the first second it doesn't have tension it will coil around me like a snake and not let me out.) I don't think it's technically "Copperweld" brand but my span has been up for 4 years between two trees now (with pulley and counterweight) and I am very happy. I am sure if I had gone with 18 gauge or similar it would have been strong enough too. This is strong stuff.

[NO9E]

Not sure whether the effort of copperweld is worth it. With flexible support (pulley with weight), a regular copper wire does very well. Too strong wire can wreck havoc when something else breaks (e.g., branch). Kinking is simply irritating.

I have a 80m dipole made of solid 14 gauge copper wire fed by ladderline. It is between the trees with one side with a pulley and a weight. The attachments broke twice but not the the dipole.

Ignacy

[N4NYY]

I screwed the pooch on this. I accidentally order an 80M phone trap instead of a 40M. I was thinking 80M phone for the length of the wire, and just had a brain fart. Luckily, I told Unadilla and blamed myself. They are going to send me another trap. I returned the wrong one already.