Ladder Line

Overview

Ladder line, also called open wire or window line, is a balanced feedline of two parallel conductors kept at a constant spacing by insulating spacers. Because most of the field travels through air rather than a solid dielectric, its loss is far lower than coax of comparable size.

The price is that it is unbalanced-sensitive. It must be routed away from metal, kept clear of the ground, and fed into a balanced tuner or a balun. It also radiates if it is not properly balanced, which can cause interference. Used well, it lets a single doublet cover many bands with very little loss.

Bands and modes

Band coverage

Modes

Safety note

Using it well

• Keep the run clear of metal gutters, downpipes and wiring.
• Feed it into a proper balun or a balanced tuner, not straight into coax.
• Twist the last few metres into the shack to reduce radiation inside the building.
• Inspect spacers each spring — UV damage causes short circuits after a few seasons.