Copyright © 2002 - 2019 by Harold Melton, KV5R. All Rights Reserved. Rev. 02/19/19
No one seems to know what to call it: ladder-line, windowed ladder-line, window line, “true” ladder-line, open ladder-line, open feeders, etc. etc.
- Twin-lead is the 300-ohm TV antenna line. Don’t mess with it. A similar line is called tubular, the type of TV line that is oval and contains a foam dielectric. It's almost as lossy at high SWR as coax.
- Ladder-line uses mostly air as the dielectric. The wires are separated with spreaders or window-punched plastic.
- Windowed ladder-line (WLL) is just that: 1-inch twin-lead with windows punched in it. Some call it window-line.
- The “true” ladder-line is best called “open-wire feed-line,” or simply open-line, to distinguish it from window-line. This is the type made from two parallel wires, separated by spreaders.
What to Get
Get the 16- or 14-gauge stranded window line from Cable-Xperts or Wireman. Don’t get that 18-gauge solid-wire stuff—it breaks when repeatedly flexed. Well—some people swear it lasts forever. I guess it will if you completely immobilize your connections.
Brew Your Own
The one problem with window line is that it tends to change characteristics when wet, and the longer the run, the more tinkering you’ll have to do with your tuner as the weather changes. The solution to make your own open-wire feeders. It isn’t hard or complicated.
- Get a 500-foot roll of #14 THHN or THWN insulated stranded (
$20~$45 at builder’s supply). Pick a color that blends with the background. Get some pressure-treated 4x4s, 12 feet long, and plant them in the ground every 50 feet or so. Many people do not use any poles; they just swag it from the tower to the eve of the house, and it works fine. Poles would be needed for runs over, say, 50 feet or so. It depends on what wire you use, how much ice you get, etc.
- For spreaders, all you need is some kind of small, UV-resistant, semi-rigid plastic pipe, like 3/8" PEX. Cut them 4 inches long, and make enough to put one every 4 feet in tensioned spans, and every 2 feet in slack spans. You can notch, or drill holes, in each end of each spreader then glue them in place with Silicone caulk or hot-melt glue. You can also purchase pre-made snap-on wire spreaders called Ladder-Snaps. I used Zareba Ribbed Tube insulators, which are made for electric high-tensile fencing, placing them between the wires and running a thin zip-tie through the middle (twice) and arounde the wires. (See my 80-Meter Doublet article).
- String up two strands of the wire, appropriate length, between trees. Pull them even. Install spreaders. You can make a 150-foot ladder line in a couple hours. It’s a good idea to continue the same wires on past the spreaders, to form the dipole. Then you have no solder connections to seal or break. Another thinkg you’ll need to have a 300-foot open-frame tape measure (~$20 at Harbor Freight).
- Congratulations - you just made modern, high-quality “true” open-wire ladder-line, and you didn’t even have to boil a bunch of wood dowels in paraffin!
- Now attach it to your supports with little electric fence insulators (on wood posts) or PVC pipe stand-offs (up the tower), as needed.
Note: Some say you have to use bare wire - baloney. Why mess with wind static, rain static, and corrosion? The same holds true for all wire antennas. Never use uninsulated wire. It just isn’t necessary. Of course, if you already have a bunch of it, feel free, and maybe spray paint it…
One more thing to consider: Bending ladder-line at sharp angles can cause problems on the higher bands. This is because the magnetic field around the line will interfere with itself at the bend. Or so say the books! I have never had any problems bending window line at 90-degree angles, and I’ve even fed a 2-meter beam with window line, bent 90 degrees 3 times, and it worked fine.