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Tower is up and pre-stretched multi-strand 14 Ga wires are cut & terminated for a multiband fan-style dipole antenna system. Location is the desert southwest of the USA.

Stringing up parts of it are going to be a challenge due to topography, and it will require lengthy tie-down cord on the end of the 75/80 Meter portions. Monofilament would definitely stretch and break down in the sun.

So I'm intending to use paracord and have a quantity of Mil Spec 7 Stranded Type III Nylon black paracord on hand.

My question:

1) Will paracord hold up well enough in the hot sun? And does the color matter? i.e., will black paracord degrade noticeably faster than white?

2) Is there a better alternative?

FYI, I used the same antenna wire mentioned here:

HF SWL antenna wire? Will plain 16-Gauge copper wire work well enough?

SDsolar
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2 Answers2

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Paracord is a usurped and abused term for a wide variety of cords. The US Military previously specified 6 different types of paracord. It is also known as parachute or 550 cord. Originally constructed of nylon to allow shock absorbance in parachutes there are now many made of polyester and other materials.

When considering its use for supporting an outside dipole there are three things to keep in mind: UV resistance, stretch and working strength.

A UV resistant material should be used for outdoor applications or the material will turn brittle and ultimately yield. Nylon, for example, deteriorates under long term exposure to the sun (UV). Check the supplier's specification and pick a UV resistant version. Color itself will not be a factor in UV susceptibility if the cord is already UV rated although some colors may fade under long term exposure to the sun.

Paracord was originally designed to stretch. This may be helpful in providing some wind survivability for the dipole if stretched between trees, for example, but too much stretch may make it difficult to properly tension the dipole.

A dipole with a balun and coax cable can require considerable tension in order to attain the desired catenary droop. You can use on-line calculators to determine the minimum working load for the paracord or simply use a pull scale (fishing, luggage, etc.) on your installation to measure the applied tension to ensure you are operating below the working load of your paracord.

If your supporting cord will rub against trees or other supports, you should take measures to guard against abrasion or choose an abrasion resistant construction.

If you are not committed to using paracord, there are several cords suitable for antenna applications. Mastrant by DX Engineering or Amazon is one such example.

SDsolar
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Glenn W9IQ
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  • TNX, Glenn, especially for the link. I'll order a spool when I have a few more items in the cart at DX Engineering. (They want 12.95 for "handling" of a 38.99 spool but it is free for orders over 100). I get what you're saying about the stretching. The longest run I'm most concerned about runs right over the solar plant and where people walk, so droop is indeed an issue. Tower is about 25 feet high. Conversely, need to make sure that it isn't too tight or fastened too high to a tree trunk across the creek lest the wind break something as the trees sway. – SDsolar Apr 01 '18 at 16:02
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    I wouldn't say color is irrelevant. A darker color means more pigments, and pigments block UV before it can break apart polymers. It's why UV resistant zip ties are black for example, and why darker deck stains do a better job of protecting the wood. – Phil Frost - W8II Apr 01 '18 at 16:54
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    Another place to look for products and information is The Wireman. – Pete NU9W Apr 02 '18 at 13:26
  • Consider looking at cordage that is made for sailboats.Some boats use non-metallic, low-stretch, high-strength cordage for standing rigging that is always exposed to sunlight. – Solomon Slow Apr 03 '18 at 20:24
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    All good info. TNX. I bought a spool of Mastrant and it seems very similar to the Mil Spec 7 Strand Type III Nylon paracord I have on hand - just more expensive. In any case, it should work. I notice it is pigmented to be fairly dark, too. At least in visible light. Hopefully will do the same in terms of keeping the UV off the strands. – SDsolar Apr 05 '18 at 16:40
  • @SDsolar Sounds good. When you get some installed, maybe you could report back so we can all learn from your experience? – Glenn W9IQ Apr 05 '18 at 16:59
  • OK, now I have used it and although the designs are similar, the outer sheath of Mastrant is woven much more tightly than the paracord - so it is much more like rope in that it does not stretch as much. It is a much better choice for the longer run I needed because it allows easier adjustment of tensioning. Excellent suggestion, Glenn. TNX – SDsolar Apr 06 '18 at 16:58
  • I've used wireman black dacron for years to hold up my antennas. I think my first run was up at least 4 years. When I took it down, it had no stretch left and was a bit stiff, but not near breaking. (I took it down to change the geometry of the antenna location.) I believe if you buy a spool from wireman, it comes with a weight rating. – user10489 May 02 '18 at 23:36
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It does work well although weather will eventually get to it. I got at least 10 years out of some salvaged from an old chute probably made in the 50s. Used to support a dipole made of #3 wire (some old 100 A drop line), both for the centre uphaul (always use a loop so you can pull it down when, not if, the feedline connections break) and for the ends tied to trees. When it broke, replaced with UV stable black rope sold for this purpose. I got mine from Davis RF.

A related tip: soldered joints on wire that needs to flex is a bad idea. One thing that works well are Marrettes - the electrical wiring twist-on connectors.

Mike Waters
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George VE3YV
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