Ladder Line

Copyright © 2002-2015 by Harold Melton, KV5R. All Rights Reserved.

Why Use Ladder-Line?

To efficiently feed a non-resonant multi-band antenna.

Antenna Mythology


First, let's dispel the greatest myth in antenna theory: Antennas must be “resonant” to be efficient. Baloney! It just ain’t so!

Please recognize that an antenna need not be resonant in order to be an effective radiator. There is in fact nothing magic about having a resonant antenna, provided of course that you can devise some efficient means to feed the antenna. Many amateurs use non-resonant (even random-length) antennas fed with open-wire transmission lines and antenna tuners. They radiate signals just as well as those using coaxial cable and resonant antennas, and as a bonus they usually can use these antenna systems on multiple frequency bands.

ARRL Antenna Book, Ch. 2

As long as the length of the antenna is at least a half-wavelength at its lowest intended frequency, its efficiency is well over 90%, just like a resonant dipole. The problem is getting power to it—coax is very lossy (due to dielectric heating) unless terminated into its characteristic impedance, and this effect is what leads most hams to erroneously believe that non-resonant antennas are inefficient. But the problem isn’t non-resonance, it’s high SWR on coax.

On the other hand, ladder-line does not suffer from high losses at high SWR, so may be effectively used to feed an antenna that may, at various frequencies, present the feed-line with any SWR from 1:1 to ~10:1. So, with ladder-line, you can completely forget about resonance and SWR, until you get to the radio, where you use a tuner to make the match to 50 j0 ohms.

To compare mismatched feed-line losses we have to start with the antenna’s feed-point impedance, and the line’s impedance, then calculate the SWR, and finally, the loss of each feed-line-type at a given frequency and length.

For a worst-case example, feeding a voltage node (like running 40 meters on an 80 meter dipole), let’s say the feed-point impedance is 3500 ohms. With 100 feet of RG-8 coax at 7 MHz, that's a whopping 65:1 SWR, with a total loss of 78%. With 600-ohm open-wire line, the SWR is only 5.8, and the loss is 3%! Then, if we switch to 80 meters, the impedance is 50 ohms, the SWR is ~12:1, and the loss is 7%. In this case, 450-ohm line would be even better, because the SWR only varies from about 9:1 at 50 ohms to 7.7:1 at 3500 ohms. The total losses for 100 feet of 450-ohm windowed ladder-line, at 9:1 SWR, ranges from 5% at 3.5 MHz, to 14% at 28 MHz, and again, that’s at the worst-case mismatch points.

So we see that ladder-line is not only better for non-resonant antennas because of its much lower loss at high SWR, but also because its characteristic impedance places it nearer the center of the antenna's impedance range, from lowest (odd half-waves) to highest (even half-waves).

See also: my feed-line calculator -- you can have hours of fun with that!

Handy formula: VSWR = (1+r)/(1-r), where r = (Zl-Zo)/(Zl+Zo), where Zl=load impedance and Zo=line impedance, in ohms.

Tuner and Balun Loss Myths

Another popular myth is that antenna tuners are very lossy and waste a bunch of power. Baloney! A T-tuner is about 95% efficient, and an L-tuner (like most auto-tuners) is about 98% efficient. If your tuner is getting hot, you definately have something wrong in the antenna system, and are exceeding the design limits of the tuner.

On the other hand, baluns can be very lossy or very efficient, depending on the design and how they are used (or misused). As with tuners, if they are getting hot, they are wasting power, and you either need to change the feed-line length, or buy a better balun. Note that there are many baluns being sold that aren’t even real baluns, like the 4:1 current balun with only one toroidal core. Any real current balun will have two cores, and be well-engineered.

Ladder-Line Myths

Many hams refuse to use it because they are afflicted by common misconceptions:

  1. “Ladder-line radiates!” Baloney! Ladder-line does not radiate any more than does coax, if feeding a balanced antenna, like a center-fed wire. If the power in each conductor is equal and opposite, we have complete phase-cancellation, and thus, no RF radiation. (This is NOT true for off-center-fed antennas, like end-feed, or the various Windom-type feeds, where feed-line radiation is significant enough to warrant a bunch of power-wasting chokes.)
  2. “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 40, 80, and 110 feet work well. A resonant length of ladder-line, just like the shield of coax, will pick up RF (common-mode induction) from the antenna and re-radiate it into the shack. However, while the coax shield is grounded, giving induced currents a place to go, ladder-line is not grounded, so there's no place for induced currents to go, except for reflection, if the ladder-line is near a resonant length. A non-resonant length will present a high impedance to common-mode current reflections. And, as with any feed-line, it’s best to run it perpendicular to the antenna as far as you can so the magnetic fields from each half of the dipole will cancel each other instead of inducing common-mode current in the feed-line.
  3. “It’s too hard to work with! You have to keep it away from metal!” Well, yes, a few inches or so. The general rule is: at least twice the width of the line. It’s easy to make stand-offs from small PVC pipe. Ladder-line can cross a metal edge, like a window sill; you just don’t want to run it right against metal for any significant length. Like, 8 feet right against metal would be too much at 28 MHz, where you'd have ¼-wave of inductive coupling.
  4. “It’s too hard to bring into the shack!” Baloney. There are many waterproof ways to bring ladder-line into any shack. One is shown later in this article (brass screws through a plastic window). You could also use parallel coaxes to make your entry, or simply mount your balun outside the wall and come in with a few feet of coax. If your wall is non-metallic, you can simply drill two small (~1/8") holes and bring two #12-#14 wires through, then caulk, and connect them to the balanced output of your tuner with banana plugs. Simple!
  5. “I can’t buy a lightening arrestor for ladder-line!” So just make them yourself, as shown later herein, using sparkplugs.
  6. “It flops around in the wind, and it breaks too easy!” (a) Windowed line should be twisted about one twist for every two feet to prevent wind-induced oscillations. (b) Make a good feedpoint connection, with proper strain-relief. It doesn’t hurt to wrap it over the top of your feedpoint insulator and then secure it to itself with cable ties. Also, the 14-gauge stranded is much more reliable than the 18-gauge solid line.

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 75% of your power in your coax when operating on bands where the non-resonant dipole presents a high feedpoint impedance to the feedline.



44 thoughts on “Ladder Line
  1. I made a FAN multi-band dipole for 160,75,40 meters what can I feed it with should it be coax or ladder line and if I use coax to feed it do I need a 1:1 balun the tuners I have is Palstar AT5K and a Palstar AUTO Tuner and let me know how long the feed lines should be and should I use coax or ladderline and should the ladder line be 300,450,600 ohms I have a Ameritron linear amp also it is a 1500 watt one it has a 3cx1500a7 my email is for more information we can talk about these things.Paul Wozniak kb9vwd

    • If you’re only gonna use it on 160,75,40 (and maybe 15) and you trim the dipoles for a pretty low SWR on those bands, you can use coax.
      If you also wanna use it on its high SWR (non-resonant) bands (20,17,12,10) you should use ladder line.
      If you use coax, you might put a good 1:1 current balun at the feed-point and (for high-power ops) a choke (the kind with ~10 stacked ferrites) on the coax before it comes into the shack, to eat any RF on the outside of the shield. The coax length won’t matter if the SWR on the line is pretty low.
      If you use ladder line (450 windowed or 600 open) on the non-resonant bands, use one of the lengths specified later in this article, to reduce the amount of common-mode RF coming down the line into the shack.

      73, —kv5r

    • &OBTW — the way to fix any G5RV,
      • add wire to the ends to bring it to 130-260 feet
      • add ladder-line all the way to your tuner
      • the bigger the aperture, the better
      • the less coax, the better

  2. I see this is old not sure if I’ll get a response or not. I have the zs6bkw g5rv and have it up 35 feet or so. The ladder line is 40 so it’s laying on the ground. I see you told someone else to keep it away from the ground. So is there any other way besides a taller tower to remedy this? I haven’t ran the coax yet I have had to order a longer run, which brings me to my next concern… My new home qth I’m basically forced to run from the shack to the opposite side of the house, about 110 foot or more.. I have the coax angled away from the mast.

    • Well it’s old but you still might get a response 😉
      Ladder line, like any parallel wire with AC on it, has a magnetic field around it. Most of it cancelled out by the opposite phase of the other wire, but not all, because the two wires are not exactly in the same place and their opposite fields are not exactly overlapping.
      Now we know that AC magnetic fields induce currents in any nearby conductors — so if your ladder line is layin on the ground, or against some metal, there goes some power wasted into heat.
      So that’s the beginning and the end of keeping parallel feeders away from conductive materials. Fortunately the magnetic field decay by the the cube-root of the distance, so it aint very damn much, just a few inches, but those few inches are very importan t and must be protected.

  3. Hi,
    nice and useful information!
    Just a question..
    I’d like to mount a NON resonant dipole feeded with 20 meter of ladder line and i think i should buy a tuner.
    Should i take a balanced one (Palstar BT1500A) or also a Palstar AT2KD will work fine?
    Thank you very much for the time you dedicate in answering to me.

    • Hi Paolo,

      I’ve never used a balanced tuner because they are so expensive (2 roller inductors) and not as versatile as a regular tuner. I use an auto-tuner, just push tune button, clickety-click, talk.

      They should be bit more efficient, with the balun on the input side, it sees a match on both ends, so operates efficiently in its design parameters.

      You should read BT1500A reviews by owners, on –

      73, —kv5r

  4. So I’m a bit confused, from a radio perspective, is there any difference between a ladder line and an otherwise identical twin-feed without the ladder cut outs?

    I seem to recall that the very presence of the insulator coating has a major effect on propagation within the wire, so I suspect an “open” ladder with no insulator on the wire between the rungs would be different than the stuff I find online, which is essentially normal twin-feed with rectangles cut out of it. Or is it different? Or is either different?

    • Yes, open-wire ladder line is a little bit more efficient than window line. In practice, there’s a lot of difference between coax and any type ladder line, but little difference between window-line and open-line.
      Window line gets a bit more lossy when wet, which is when open-line is better.

  5. I’m a little new to the hobby , just know enough to be dangerous,, I am thinking about putting up a 5 band 2 element quad but i would have to either run 5 coax lines or run an antenna switch , I don’t want to do either , could I run open line and just tie all the lines together , what do you think ?

    • I don’t think it’d work. Multiband elements on one feedline “select” the proper element (for a given frequency) by its feedpoint impedance being closest to the feedline’s impedance, a condition where maximum energy transfer takes place.
      Feeding a bunch of loops, whose feedpoints are ~50 ohms, with 450 ohm LL, it won’t “select” the desired driven element, but one closer to 450.
      It might work if you just tie all the feedpoints to one 50-ohm coax and run that in. Even then, adjusting all 5 loops to 50j0 in each band will be an endless nightmare, because they interact both with each other and the reflector loops as well. Model it in MMANA first and see!
      I think you’d be better off building a spider beam, there’s plenty of plans and kits for those, they’re simpler than a quad, and from what I read they work pretty well.
      I’ve never built either one so that’s just IMO.
      73, kv5r

      • It is similar to the case of a multi-band dipole that uses separate, different length legs all joined at the center. Only the legs tuned for the band in use present a matched impedance and radiate.

        The feedpoints for quad loops are actually about 100 ohms *at the frequency it is tuned for*. The other loops will be higher or lower in impedance and thus present a mismatch and not radiate or not radiate much.

        In this situation, I have successfully used a 2:1 balun at the point where the loops join and fed it with coax.

        The real problem with feeding a quad or any other rotating antenna is keeping the ladder/window line away from the tower as it rotates.

        Thus, I’d recommend using ladder/window line up to the bottom or mid-point of the tower and coax the rest of the way. You can make a matching transformer between the window line and coax at that point using window line or some other method.

        • Yes all well and good, except he wanted to run multi-quad-loops on a single ladder-line without a switch, and that ain’t gonna fly. It’s not like a ~50-ohm fan dipole on 50 ohm coax.

          And while a 1-wl loop is 100 ohms free-space, it’s much lower in the presence of parasitic elements. Just like on a yagi the DE in free-space is ~72 ohms, but with R & D parasitic elements it’s like ~20 ohms. You can’t expect a 450-ohm LL to select the right DE by impedance matching alone, (unless the DE’s are 450 at the feedpoint, maybe a big delta-match might do it), otherwise you’re gonna need a box full of relays up there.

          Putting LL across a rotator isn’t hard at all, you just hang a big ol’ loop out there and it’ll spiral 180 degrees either way just fine, if it’s big enough it won’t touch the tower.

          73, –kv5r

  6. Thank you for an interesting web page, I had been intending to run openwire for the last 30 years but only recently did.
    The aerial was cut as a standard halfwave dipole on 40m, initially fed with 80ft of RG58. Changing to openwire with old school seperators made from wooden dowel the 40m results of course did not change much. However running the aerial on 20m where the impedance is very unfriendly was an eye opener! Pretty good on all bands 40m and higher, as you mentioned I also don’t believe in the single core 4:1 current balun, I used two seperate FT240-43 rings each with simple twinflex as a bifilar winding, all driven by a t-match atu. I have since taken this balun apart in favour of a 1:1 current balun. I experimented with different core types and windings, some efforts got pretty hot at high power and did not have very high common mode impedance. The cores I am using are working well for me. I intend to arbitarily lengthen the aerial to avoid resonances, just to defy the masses! Best regards David G0FVT

  7. That should read not high enough and no I don’t use the 949e anymore since I have a auto tuner in my Ken wood Ts 570. Balun between ladder and rg8x coax should be removed right? K8BLS

    • Well, not necessarily. Every installation is different and if it’s working well with the balun, just leave it. Or remove it and see if it’ll still tune on all bands with your radio’s internal tuner.

      You’ll probably see some improvement if you cut off most of that excess RG-8X you have coiled up; that’s gonna be pretty lossy at bands other than 20M. If by “way more” you mean like 30-50 feet, yeah trim that off; if it’s like 10 feet or less, don’t mess with it.

      73, –kv5r

  8. I like the g5rv I installed in 2001. Your right it never tuned right unless you had a tuner which has a 4.1 balun in it (mfj 949e) so I got the idea to put a 4.1 between the coax and ladder line, guess I should remove it. I have the AT in my Ken wood ts570 so it does fine. The leads from the center touch nothing, but the ladder line lays on the house flat roof tar roofing and the center is hooked to my brick chimney about 35 feet from ground level. I have never been able to get amps to work right but the 100 Watts works good 1.1 swr. I have way more rg8x than needed so just coiled it up. I’ve been told its not night enough and using it as a inverted v is bad, they say flat topping would be better. G5RV 10 thru 80 meters is what I have center feed ladder to rg8x coax cable. Good day. K8BLS 73’s

  9. I was thinking of using ladder line to feed a 2 meter/70cm antenna. Is this a bad idea? I can’t seem to find an antenna tuner for these bands.

    • It will work for 2 meters but probably not for 70cm. I seem to remember reading somewhere that the line width needs to be under ~1% of the wavelength.
      My first 2-meter antenna was a 10-element yagi built from old TV antenna parts. I modeled it (with MMANA) to use a folded dipole driven element and spacing such that the feedpoint was 370 ohms, then fed it with with 1″ #14 LL, which was 370 ohms. On the radio end, I matched it with a simple L-tuner I made, which was 1.5 turns of #12 solid, 1/2″ ID, and about 6″ of RG-58 for the capacitor (designed using some old software I don’t remember). That connected to a couple feet of RG-8X to a little VHF SWR meter. By removing the outer jacket of the RG-58 stub and taping the end of the shield, I could scrunch or stretch the shield and thus adjust the capacitance. It went flat at one point! That antenna worked great and I regularly hit repeaters at 125 miles.
      I built that because the local ham guru told me it was impossible to use ladder-line on 2-meters!
      73, –kv5r

  10. Thank you for this excellent site and blog. I have a full wave 80 m delta loop that is fed with a Q section of RG11 connected to 50 ft of RG8U then into the rig with a 1:1 SWR at 3.8 Mhz. I tried 450 ohm ladder line to an external tuner next to the rig and was getting a lot of RF in the shack. If I use about 20 ft of 2 sections of parallel RG8 center conductor into the tuner should that help in reducing the RF in the room? Also in your opinion how much better percentage wise is ladder line versus a “Q” section in this configuration? I’d like to use the ladder line for multi-band use. 73, Gary W8vi

    • Well, as explained in the article, ladder-line has much lower loss (almost none) than coax, at high SWR.

      I’ve never tried q-section matching (which is good for 1 freq only); or parallel coax feeders. I think that running your ladder-line to parallel coax feed-line (shields tied together at both ends, grounded at 1 end) should perform like ladder-line but without the RF in the shack problems. Parallel coax feeder does not suffer high loss (at high SWR) like a single coax.

      Another thing worth trying is use ladder-line to tuner like you did, but change the length to avoid common-mode resonances on the line, which is the usual cause of RF-in-the-shack problems with ladder-line. Good lengths to use are listed elsewhere in this article.

      Many hams just run a short coax to an outdoor balun. However, baluns are also lossy at high SWR, but with ladder-line you’re either using the tuner’s internal balun, or remoting one outdoors away from the shack a bit, so losses will be about the same either way (I think), assuming similar balun design. And in either case, it should be a two-core current balun; the single-core ones are a hoax and are not baluns at all (according to some RF engineering articles I read a while back).

      Vy 73, –kv5r

  11. what is better using a G5RV with a 450 ohm or 300 ohm ladderline ?
    which will have a lower SWR using an
    external tuner the 450 ohm or 300 ohm ladderline ?
    what is the difference between the Truetalk G5RV 450 ohm antenna and a
    G5RV antenna using 300 ohm using a balum at bottom which antenna is better ?

    • It’ll work with either 300 or 450. Varney’s original design used 300, but US-made ones use 450 just because of its availability. Either one will need a tuner except perhaps on 20 meters.

      You don’t need a balun at the ladderline-to-coax connection, the length of the ladder-line does the impedance transformation to 50 ohms (more-or-less), that’s why it’s a specific length. Of course, people selling them with baluns will say otherwise 😉

      A balun is always wasteful and IMO should never be used unless there is some problem that can (and indeed will) be solved by using one.

      73, –kv5r

  12. Built a parrell dipole that is centered on 3915 and 7200 fed by RG213u coax, my first thought was to run
    NR14# LL had about 100′ that was to much LL hang on my roof it moved around some with the winds at this QTH though I better use coax an have. My question is, Do you think thereare shorter leanths of 450 LL
    that could be used to get a match both on 75m & 40m with a tuner using 80′ or less feet 450 LL?
    Thank You, Walter

  13. I am thankful for information such as this. I wanted to note that I attempted to run ladder line along a copper roof cap for about 8 feet. I stood it off from the cap using wooden toilet paper holders that were about 6 inches high. Not a good solution. Running along that length, at that distance, my SWR wouldn’t go any lower than 2.0 on most bands, whereas it was 1.1 to 1.3 without running it that way. I am now fashioning away to avoid the metal as much as possible.

  14. Thanks for the blog i found it very useful,just about to use 3oo ohm ribbon for the first time on my 40 meter loop. Having probs getting supported high enough being vertical. many thanks again 73s


    • 300-ohm ribbon, if you mean the TV type, is pretty lossy. It’d be better to use 1″ windowed, or even better, 3-6″ open-type ladder line.
      There is a 300-ohm 1/2″ windowed line (hard to find), that would probably be OK. The general rule is, the less plastic dielectric between the wires, the better. A line with a 95-98% velocity factor has so low loss you can forget about SWR-induced line loss.

      See also my feedline calculator — for example, for a 100′ line at 14 MHz with a 10:1 SWR, RG-8 will lose 44%; 300-ohm tubular (that oval stuff) is 31%; 450-ohm WLL is 11%; and 600-ohm Open-wire line is 8%. Big difference!


  15. whats a good 450ohm line length longer then 86ft , i think my run now is about 120-130 ft… the hard part is the run across the roof from the tower to the shack it whips around alot in that span and i don’t really want to poke more holes in the roof for supports.

    I found a nice static drain and lightening/emp protector and find a 9ft coax line works well from the balun to the auto-tuner
    please see photo’s on my page.

    • Nice setup you have there!

      The next non-resonant length would be around 110 feet.

      You need to put twists, at ~1 twist per 2 feet, in windowed ladder line to keep it from flapping around. The twisting cancels aerodynamic oscillations. After you put in the twists, all it will do is just swing back and forth a little in the breeze. Mine spanned about 60 feet horizontally without problems.


      • Including twists to cancel wind effects sounds like a good idea. But I’m guessing that in cases where the feedline is also part of the antenna (G5RV) twists may degrade. Unsure … ? My G5RV has no intentional twists in the ladderline, and has been awesome over 16 years, 8Band-DXCC, etc.

        • The ladder-line part of a G5RV is not a radiator, it’s an impedance transformer, so putting a few twists in it should not be a problem. Indeed, most parallel line is “twisted pair.”
          The reason it doesn’t radiate is because it’s terminated in a balanced load (the 102′ center-fed dipole), which causes 180 degree phase cancellation in the feed-line.

  16. Ok new guy here …g5rv using a alum military pole on my rv im portable they are saying not to have ladder line up aginst the metal pole but what if said pole is isolated from ground..? Im in the oilfields of southern texas fulltime rver so trying to be more portable than most….jimbo

    • It’s doesn’t matter if the pole is grounded or not. If the ladder line is too close to it, the line’s magnetic field will induce RF into the pole, thus turning some of your power into heat. You can make stand-offs pretty easily with 1/2-inch PVC. Make them ~6 inches long; drill a hole thru each end; secure the pvc standoffs to the pole with cable ties (or wire); and secure the ladder line to them with cable ties (or monofilament fishing line).

      Hey where in Southern Texas? I grew up in the RGV, near Harlingen.

  17. Ladder line at 14 or 16 gauge is a bit pricey when running 100 ft. How about using some spacers and tie wrap to make true (not windowed) ladder line?

    • Sure, true ladder line is best, if you don’t mind the work of making it. It will perform a little better than windowed line, particularly when wet, and have lower wind-loading. I’d use #14 insulated stranded THHN wire (or #10 for high-power), and perhaps some 1/4-inch thin-wall UV-stabilized acrylic tubing for the spacers (3-4 inches), notched on each end using a suitable jig on a router table (or similar); pull two wires taut between trees, insert notched spacers every 3-4 feet, and glue ends with silicone caulk or hot-melt.
      Of course, any copper wire it way too expensive nowadays. I once made ladder line from #17 aluminum (electric fence) wire, and pieces of plastic clothes-hangers for spacers, and it worked OK for a 50-foot or so run.

  18. On a G5RV how close can I come to a 4ft chainlink fence with the latter line? Also can part of the latter line touch the ground? I plan on burying the coax run thru the back yard to the house.

      • I also am running a G5RV. Im new so forgive my stupid question. I have about 60′ from the shack to the feed point at the ladder line. Can I feed w ladderline to decrease loss, can the feed line be buried. My plan was to bury RG-213 in pvc to feed it but I wanted to find the lowest loss method.

        • The ladder-line on a G5RV is a matching section and its length should not be changed. It provides a fairly low SWR on all HF bands (except 15), so feeding it with coax should not be excessively lossy.

  19. Was wondering about the interaction between the ladder line from a G5RV feedpoint to a balun and a 5mm wall aluminum pole that is supporting the G5RV feedpoint. Since I was going to rig up a pulley on the feedpoint pole to lower and raise it in need, what should I do about keeping ladder line away from supporting pole?

    73 de ZR1HPC

    • Hi,
      You need to keep the ladder line away from the pole, at least 2x-3x width of the line. You could bring the line away from feedpoint at an angle, or mount your pulley on an angle-bracket to offset the feedpoint about 15-20cm from pole then bring ladder line down parallel to pole. Either way you need to mount the balun to a stand-off bracket of some kind. Be sure to put a few twists in the ladder line so it won’t flop in the wind like a ribbon.
      73, –kv5r

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