All About Ham Radio Ladder-Line
Copyright © 2002, 2006 by Harold Melton, KV5R. All Rights Reserved.
Amateur Radio Ladder-Line: Page 6
Continued from: Page 5
Watertight Entry Assemblies
This assumes your rig is near a window, and you know how to replace a window pane with plastic. I used a window because my trailer-home has metal siding. If your walls are nonmetallic, you can, of course, go through with long threaded brass rods. This may be easier than replacing a windowpane with polycarbonate.
Remove and disassemble the windowpane. Measure the glass, then discard and replace with polycarbonate of the same thickness. Many hardware stores carry small pieces, and one shouldn’t cost over a few dollars. Cut the new plastic pane to the exact dimensions of the removed glass. Reassemble the window.
Plastic sheet is best cut with a circular, table, or radial-arm saw, using an 80-tooth finish blade (hollow-ground or carbide — do not use a “set-tooth” blade) and cool with a little trickle of water. Don’t use a jigsaw, as they just make too much heat. Apply masking tape to avoid scratches during cutting. You may be able to find a store with a commercial panel cutter that will do this for you, and save all the mess and trouble. Take exact dimensions.
Note: It is possible, with a special bit, to drill glass. Don’t! If a big storm comes along and a tree limb falls on your ladder-line, it’ll probably rip out the window glass - not exactly desirable, particularly during a storm…
Fabricate the feed-through assemblies using 10-32 brass hardware as shown in Figure 2. You’ll need (2) 10-32 x 1½ screws, 10 nuts, 4 brass washers, and 4 flat rubber sink faucet washers (as seals). Drill the two holes through the window, spaced the same width as your ladder-line. Attach the ladder-line on each end using soldered ring lugs. Split the rings open with wire cutters, place over the outside end of screws, then close the rings and tighten the nuts. Cover outside connections with Coax-Seal (see mine corroding?).
If you’d rather go through a wall (nonmetallic houses), get the appropriate lengths of small brass all-thread rod, and the same length of Tygon tubing (the thick-walled variety) to slip over and insulate the rods. Then get the appropriate extra-long drill bit (carbide-tipped for brick, if needed). Don’t drill into a pipe or electrical wire! Drill the holes through the wall and insert the Tygon-insulated rods. Put double nuts and washers on each end. Caulk the outside entry points. Solder ring-lugs to the feedline and jumper. Grease the rings. Install and tighten. Waterproof the outside ends with silicone caulk or Coax-Seal. You’ll then have a permanent ladder-line entry that’ll last as long as your house.
Figure 2
Many people seem to miss the KISS principle. You can take a 1-by-4, cut to the width of your window, paint it with exterior house paint, wrap its edges with foam weather-stripping, put it in a window and close the window on it. Then cut a length of parting stop (door molding) to use as a jamb-stick to lock the window down against it. Then you can drill it to your heart’s content and bring in all kinds of cables, all without drilling your house. Works great for renters.
The Quick-Disconnect Jumper
The short jumper on the inside goes from the feed-through bolts to the balanced output of the antenna tuner. Solder banana jacks onto the line and just plug them in. When thunder is heard, jerk them out and bend the line well away from equipment. This is a lot faster and neater than using the cross-bores in the binding posts, and will encourage you to disconnect at every sound of thunder. However, the bananas might not handle the high current of QRO operation. Since I run barefoot, this is not a problem. A good old-fashioned double-pole knife switch is an even better option - and they look so cool!
Figure 3
