Ladder line is great – Its extremely low loss, even at high SWR. Its cheap to build and extremely simple to install. However, many hams refuse to use it because they are afflicted by common misconceptions. When you take the time to understand it, its easy to see why hams have loved it for nearly 100 years.
Types of Ladder Line:
- Twin-Lead – This is the 300 ohm TC antenna line. Avoid this if you can.
- Window line – This is typically 1-inch twin-lead with windows punched in it.
- Open wire – This is the true ladder line. Its made from two parallel wires, separated by UV resistant insulating spreaders.
Common Misconceptions of Ladder Line:
“Ladder line radiates!” – Baloney. Ladder line does not radiate any more than does coax, if terminated in a balanced antenna.
“I tried it once, and it messed up my TV, my computer, and filled the shack with RF!” – The trick here is simply to make sure you use a length of ladder line that is not a multiple of a half-wavelength on any band. Lengths like 43 and 86 feet work well. A resonant length of ladder line, just like the shield of coax, will pick up RF from the antenna and conduct it into the shack. The only difference is that the shield of the coax is grounded, and the ladder line is not, so it acts in common-mode to bring in and radiate induced RF. Again, simply avoid those resonant lengths.
“It’s too hard to work with! – You have to keep it away from metal!” Well, yes, a couple inches or so. The general rule is twice the width of the line. It’s easy to make stand-offs from half-inch PVC pipe.
“It’s too hard to bring into the shack!” – There are many waterproof ways to bring ladder line into any shack.
“I can’t buy a lightening arrestor for ladder line!” – So just make them yourself. Here are a few links.
“It flops around in the wind, and it breaks too easy!” – (a) Windowed line should be twisted about a turn every two feet to prevent wind-induced oscillations. (b) Make a good feed-point connection, with proper strain-relief. It doesn’t hurt to wrap it over the top of your feed-point insulator and then secure it to itself with cable ties. Also, the 14-gage stranded stuff is much more reliable than the old, cheap 18-gage solid stuff.
If you run an all-band dipole (with a tuner in the shack), you need ladder line. Coax is very lossy when operated at high SWR. It’s easy to lose 90% of your power in yourcoax when operating on bands where the non-resonant dipole presents a high feedpoint impedance to the feedline.
Classic Multiband Dipole – By Steve Ford, WB8IMY, QST, March 2004
Open Wire Feed Line – A Second Look – By Paul Danzer, N1II, QST, April 2004
The Lure of Ladder Line – By Steve Ford, WB8IMY, QST, December 1993
Balanced Transmission Lines in Current Amateur Practice – By Wes Stewart, N7WS