600 ohm open wire (ladderline) construction

Discussion in 'General Technical Questions and Answers' started by VA3GRV, Oct 5, 2006.

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  1. VA3GRV

    VA3GRV Ham Member QRZ Page

    Hi Folks,

    I'm looking for plans to build my own ladderline, can anyone steer me in the right direction? Can't seem to find any plans online. Also how to run it into my shack.

    73 Vince
  2. AG3Y

    AG3Y Ham Member QRZ Page

    Virtually any ARRL Antenna Handbook that I can remember ever seeing, has instructions for building open wire feeder. There are charts for wire gauge, spacing, and hints on choosing insulator material, ranging from wax-soaked dowel rods to plastic clothes-hanger rods.

    You shouldn't have too much trouble finding the book, which is available at almost any hamfest. Or do what I just did recently, and pick up a copy at a used book store in your area.

    Good luck ! 73, Jim
  3. VA3GRV

    VA3GRV Ham Member QRZ Page

    Thankyou Jim, Guess I'm being lazy hihi, Thought for sure I would have found something on the web. Maybe I'll have to order a book.
  4. W5DXP

    W5DXP Ham Member QRZ Page

    It's certainly not rocket science. W7FG uses normal #16 insulated wire and makes the spacers out of half inch irrigation tubing available at Home Depot or Lowes. Spacers are about three inches long with notches in each end for the wires. Piece of cake.
  5. AG3Y

    AG3Y Ham Member QRZ Page

    I've seen ladder line with the spacers threaded on the wire, but the easier way to do it is to make the knotches as Cecil suggests, and then use small pieces of bus wire to fasten the line in the notches. The bus wire has negligible effect on the characteristics of the feedline.

    Remember that it is really not all that important to match the antenna impedance to the feedline impedance when working with this setup, unless you are actually trying to transform one impedance to another using the line as a quarter wave matching device. Most instances I know of, that is not the case. One of the very first installations I ever saw used open wire feedline spaced about 4 inches apart, and the setup worked like gangbusters! I seriously doubt that the fellow actually had any idea of what the feeline impedance actually was !

    I'm using some commercial ladder line here, but the only "design" consideration that I used was to make sure I had enough line to go from the feedpoint of my antenna to the balun just outside the wall that I feed a short piece of coax through. Real scientific approach for this "Extra-Class Snob", but I certainly make as many contacts as I care to with the setup, so as the old saying goes, "if it works, don't knock it! "

    [​IMG] [​IMG] [​IMG]
  6. VA3GRV

    VA3GRV Ham Member QRZ Page

    Ok Thanks Guys....I thought there was a formula for the spacing.I thought I would try it, my current inverted V works good but I thought maybe I could improve by running some 600 ohm right to the tuner that has posts for open wire, rather than using the 31 ft. of 300ohm ladderline with a coax balun then to the tuner. The ant. seems pretty good I had a qso with Trinidad on 20m last night! Thought that was Cool!
  7. AG3Y

    AG3Y Ham Member QRZ Page

    Oh, there is a formula for the spacing, but that, and the wire gauge all work together to determine the actual impedance. As I said, there are charts in the ARRL antenna handbook, but the actual impedance is a fairly minor consideration as the losses due to an impedance mismatch are very minor for open wire feedline, as compared to the same type of losses for coax cable. The stuff is wonderful to work with. The only thing you really need to watch out for is to keep it a reasonable distance away from other metal. For instance, don't tape the stuff to your tower, or run it along a downspout or the gutters! Stay away from aluminum siding, and you should be OK . [​IMG]

    73, Jim
  8. VK4XJB

    VK4XJB Ham Member QRZ Page

    Z = 276 * log(2 * S / d)

    S is the centre to centre spacing of the wires
    d is the diameter of the wire

    S and d are in the same units.
  9. N9FE

    N9FE Ham Member QRZ Page

    wa3grv, if you can run your open wire right to the tuner that's the best, a balun right outside the house like ag3y did work's well to, you can also run two piece's of 'i beleve" 75 ohm coax to get you out of the house, as long as your open wire is not laying on metal, you'll be ok, i kept mine a foot off the tower with pvc standoff's, i also run right to the back of the tuner, and use the balun in the tuner, you might have to add or subtract some feedline length to work all band's,, welcome to the world of open wire, this next summer a couple of us are going to experiment with open wire for uhf and vhf, i went from s9 to 20 over to everyone, even the long hauls, mark
  10. WD8PTB

    WD8PTB QRZ Member

    Yes there is a formula but in most cases low loss is what is desired so the actual impedence is not critical. I have seen various spacing ,ussualy with #12 or 14 electrical wire, ussualy hooked up to a balanced output of a tuner. Don WD8PTB
  11. N4AUD

    N4AUD Ham Member QRZ Page

    I've used small diameter PVC pipe for spacers, people have cut up plastic coat hangers as spacers, and currently I am using "mini popsicle sticks" available at craft stores as spacers. I've used regular 12awg insulated stranded wire as a conductor and am currently I'm using some "lamp cord" that I pulled apart as my conductor. I don't expect it to hold up in the weather but for now it is working. I use "Goop" industrial adhesive to fasten the spacers once I get them in place.

    You'll have to stretch out both conductors and apply the same amount of tension to both when you are placing your spacers. If you have one wire more taut than the other, your spacers will not be straight. I just drilled holes in my popsicle sticks with my drill press and slid them on, but you can obviously cut a slit and slide your spacers on. If you are going to use PVC, plastic coathangers or some other material for your spacers and you don't have a bandsaw, it can get really tedious cutting the spacers one by one with a hacksaw. That's what led me to use the popsicle sticks and so far, to my amazement, they've held up in the weather.
  12. AG3Y

    AG3Y Ham Member QRZ Page

    Did you soak the popsickle sticks in wax? Or perhaps shellack them ? They should last for years if you did either of those things.
  13. K7KBN

    K7KBN Ham Member QRZ Page

    Depends on how the cat felt about what you were trying to do...  [​IMG]
  14. N1ESE

    N1ESE Ham Member QRZ Page

    As I am starting to build my open wire feeders, I am wondering how close together feeders need to be and whether distance between wires in the section between spreaders can vary at all? With wire like this, I don't really think it's possible for it to be a constant 4", or whatever, distance throughout the entire run. Will small variances negatively impact performance of the feedline?

    I'm using 14 ga. stranded THN as it is what I have under the bench. Two continuous runs make up the feedline and antenna elements. Using 1/2" CPVC for the center and feeder spacers.
  15. K7KBN

    K7KBN Ham Member QRZ Page

    You Could Do Much Worse Than Refer To This

    Google is, as I've said many times, your friend.

    I've made homebrew parallel line using 3/8" diameter plastic rod cut into ~4" lengths. I used a "hot knife" to cut grooves the proper width for the wire I was using, and when the wire was in position I'd take a soldering iron and melt the plastic over it, making a pretty secure condition. At least none of the wires ever popped out.
  16. N1ESE

    N1ESE Ham Member QRZ Page

    Here's the start of my open wire antenna, I am probably doing something wrong but if it works I'll be happy.

  17. W8ZNX

    W8ZNX Subscriber QRZ Page

    have used Thompsons Water Seal
    soak the wood for a week or so

    with weight on top
    to keep the wood
    under the water seal
    most likley other brands
    would work just as well

    works better than
    wax, shellac, or varnish

    man shellac !
    nobody uses shellac any more
    dam stuff is a pain to work with
    and it's more expensive
    than good spar varnish

  18. K7KBN

    K7KBN Ham Member QRZ Page

    You want to be sure the Ty-Raps®, Zip-Ties® or whatever you want to call them are UV resistant. Generally the UVR ones are black. Exposed to sunlight, the non-UVR versions will break in just a few months.
  19. N1ESE

    N1ESE Ham Member QRZ Page

    Yeah, these are probably not UV resistant but they are all I have at the moment. I need to make do with what I have according to the YL. *grin*

    This will hopefully only be a temporary antenna. I will pull it down in a few months and see how they are holding up and replace if necessary.
  20. K3STX

    K3STX Ham Member QRZ Page

    OK, I'll play the fool and say "I don't get it." If you want to do it for fun, I can see it, but are you somehow doing this because you think it will be superior to the dirt cheap window line that is commercially available?

    To put on wrap-ties that will disintegrate in a year and then replace the whole thing with 200 more wrap-ties that are UV resistant sounds like a masochist to me.

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