Ladder Line Page 6

Copyright © 2002, 2006 by Harold Melton, KV5R. All Rights Reserved.

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

— End —

17 thoughts on “Ladder Line Page 6
  1. Have a 160m shortened dipole using around 42′ of Nr 14 450ohm LL feed to a 1 to1 current balun and 6′ of RG 213 to a HF Auto tuner all is well with this setup. Question what is the next leanth LL that could work for 160-75-40m only could use about 90′ or less over all to do this job! This would raise the apex about 13′, it I could make it work. Thanks walter kb6hrt

    • Any length will work if you’re not having RF in the shack.
      80′ is the next length that’s non-resonant in common-mode on all hf bands. See page 3 of this article.
      73, –kv5r

  2. Great website, and I especially liked the ladderline article. I have been using ladderline for many years to feed my loop. Just wanted to mention that Zareba products make a superb 4 inch fin tube insulator for use in electric farm fences. These fin tube insulators make EXCELLENT spreaders for ladderline, being UV resistant, lightweight and extremely strong. Google online for a picture. Prices are very reasonable, about 10 cents each. Find therm in your local Farm and Feed store, in the electric fence department.

    • Thanks John, that’s a great idea! I’ve looked at electric fence supplies before but didn’t notice they made 4″ tube insulators.
      I’m curious as to how you attach them to the wires, drilled holes, or notch and glue, or ?
      73, –kv5r

      • Hi. sorry for the long delay in replying, I drill holes about 1/4 inch in from each end, just big enough for the insulated wirte to slip through. couple of drops of PVC glue or epoxy, will keep them secure.

  3. Great site Harold. I have a nice 80 meter inverted vee doublet up 65’on fiberglass telescoping mast fed with DXE’s 300 ohm ladder line to either 1:1 or 4:1 Palstar current balun, then short coax to Palstar AT2K tuner.

    First question: it would be very convenient (and out-of-weather) to run the ladder line down the *inside* of the (non-conductive) mast but I have read several negative comments about the inefficiencies of running non-coaxial feedlines through PVC, etc especially if buried. I’ve tried running ladder line inside the mast and know it works, but does this increase losses, etc?

    Second question: I would like to try this 80 meter antenna on 160 by running it against ground or counterpoise as a “T” or as a top hat loaded vertical or just half of it as an inverted “L”. The ladder line would ideally be run up the inside of the mast. Obviously a single conductor is called for instead of ladder line. Would it work to just short the two conductors together at the station end or would the top leads need to be shorted also (or vice-versa)? In the case of the inverted L, would it work to feed just one conductor and ignore the other half of the line & antenna?

    Please reply by regular email.

    Thanks so much! 73 – Jim, K4HSB

    • Hi Jim,

      You should be able to run your LL up thru your fiberglass mast without much loss; it depends on the dielectric constant and thickness of the mast. But don’t run it underground thru PVC, that doesn’t work, the earth around the pipe soaks up induced power from the line’s magnetic field. You’d need to cut a slot in the mast some distance above ground to bring the LL out, and that might weaken the mast. I wouldn’t risk it.

      To run your 80M dipole on 160, tie both leads together at the balun and ground the other side of it. Don’t run one wire only, the other one will sap power by induction. Tie both leads together (common-mode). You don’t need to short the top end.

      You could use a heavy-duty DPDT switch at the balun; one pole of the switch would swing the ground from balun to nothing, the other pole would swing one side of the LL from one balun output post to the other, where the the other LL wire is connected. Just make sure the switch has enough air-gap in it so RF doesn’t arc, if you run high-power. A good ol’fashion knife switch, or an RF relay would be even better.

      I’ve never run that configuration but lots of top-banders do. With your mast/feedline vertical 65′ and the dipole as a top-hat it should work pretty well as a 1/8th-wave top-loaded vertical. Lots of 1/4-wave ground radials at the base of the mast will help, if you have the space (that’d be like a couple acres!) but if you have room for 130′ radials, you have room for a 160M dipole, which, peaked at 65′, would work a lot better than a vertical w/o radials.

      I’m curious where you found a 65′ fiberglass mast. The longest ones I’ve seen on-line are like 48′, at ~$300.

      73, –kv5r

      • Thanks Harold,

        You can make the mast out of tubing from DX Engineering but if you go the full 65′ that way it is pretty flimsy way up there and needs lots of guys.

        I’m running the first 20’with pressure-treated wood and the rest with the fiberglass starting with 2.75″ diameter. The antenna itself serves as top guys and one other set mid-way. It survived an F1 tornado intact!

        73, Jim, K4HSB

  4. You got an amazing site, my friend! I have never seen so much relevant and “down to earth” info in one place. I really appreciate, and it strengthens my belief I had in home-brewing ladder lines and doublets. I run a 80 feet doublet, from the balcony of my 24th floor apartment till the roof on the 26th floor. I use NO line…the antenna starts at the tuner LOL! A refurbished AH4…..Thanks again, and keep up the good work. 73 from India, DE VU2ORO, Ron!

  5. I have a 2″ pvc pipe thru my wall which I bring coax etc into shack. My house is all metal can I place the 4:1 balun out side and use 10 foot coal into the tuner. Really liked your article.
    David KD9ALS

    • Yes, that’s a very commonly used way of doing it. Years ago, I brought ladder line to the house, coiled about 7 turns of it bifilar on a 1.25″ type 77 Amidon toroid, then used about 15 feet of RG-8 coax from there on in and it worked OK. When I eventually made the change to bringing it all the way into the tuner (as drscribed in the article), it did work just a bit better.

  6. Harold,
    Nice series of articles on balanced transmission line. Thank you. I’m thinking about the vinyl covered galvanized steel wire rope for the transmission line and elements of an all band dipole. The material is very strong, flexible an solders willingly. The vinyl clad coating should increase its usable life. It’s available in a variety of gauges. What are your thoughts?

    • I haven’t tried it or known of anyone who did, but it should work; the resistance will be several times higher than copper so size it up accordingly.

  7. Thank you for taking your time to compile your knowledge of ladder line and put it out here for us to read. I have been using ladder line for about a year. I like it much more than coax. I have two doublets. An 88′ and 44′. They perform as Double Zepps on 20m & 10m, but they tune up on all bands except 160m. I run 450 Ohm ladder line straight to the tuner. My tuner has a “Balanced” button on it that puts the signal through a 4:1 balun. (I’m sure you know that) Anyway, I have some bands in which I get a better tune when NOT engaging the “balanced” button. Is this ok for me to run it like this on those bands? I would think it’s ok. But after seeing your site, I thought I’d run it by you and see what your thoughts are this.
    Thanks Kirk / wt4p

    • If some bands tune better without the 4:1 balun in-line, then fine. I think that would mean the impedance of the line, at that point and frequency, is closer to 50 than 200.

  8. I’m a new ham designing my first station and I liked your ladder line article. Now, if possible, your suggestion on how to get the ladder line into the shack. I have a metal building that I installed a stainless steel water tight enclosure on the outer wall. There are 2 1″ holes cut into the door of the enclosure that I will use to bring ladder line/antennas in. I’m building a doublet dipole antenna 135′ long. I will have a 4:1 Balun between the ladder line and a tuner.

    1. Should the balun be mounted outside of the enclosure?
    2. If I bring the ladder line inside the enclosure are there insulators available to go through the holes? Will I be too close to metal?

    Suggestions welcome

    • I think it would be the same as an antenna tuner box that has insulators in the back and a balun inside. You should be able to bring the ladder line into the box with a couple of insulated 8-32 threaded brass rods, connected to the balun inside, then go out the back into the building with a short run (say, <~15') of coax to your tuner. The balun should be inside the box, but make sure to use a current balun (has 1 or 2 toroids), not a voltage balun (has coils usually wrapped on pvc). I'd blank off those holes in the door and bring cables in through individual, grommeted holes in the bottom - better to keep out bugs and moisture. And coming in the bottom forces you to leave a drip-loop in the cables. Then put the ladder line insulators thru the side or door. Many insulators are available, (search for RF feed-thru and feed-through), but it's easy enough to make your own, something like: rubber grommet or nylon bushing in the hole; nylon washers and double brass washers and nuts on each side; 8-32 brass rod thru the middle. Grease and waterproof the outer connections. Should work fine. If you're using solid-wire line, wrapping it is OK, but if it's stranded, terminate it with soldered ring-lugs. Could also mount a little metal plate there, on a stand-off block or bolt, very close (like .025") to the outer nuts, as a spark-gap arrestor. Then ground the box with a fat wire to a ground rod right below it. Ladder line is unaffected by crossing metal perpendicularly; what you want to avoid is running it for some distance parallel to metal, less than about 4" away. For example, if you're gonna come down the side of you metal building, simply make 6" stand-offs with L-brackets and 1/2" pvc pipe. I used the same to come 20 feet down a tower leg and it was unaffected. Hope this helps, and thanks for stopping by! --kv5r

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