Copyright © 2002 - 2019 by Harold Melton, KV5R. All Rights Reserved. Rev. 02/19/19
No one seems to know what to call it: ladder-line, windowed ladder-line, window line, “true” ladder-line, open ladder-line, open feeders, etc. etc.
- Twin-lead is the 300-ohm TV antenna line. Don’t mess with it. A similar line is called tubular, the type of TV line that is oval and contains a foam dielectric. It's almost as lossy at high SWR as coax.
- Ladder-line uses mostly air as the dielectric. The wires are separated with spreaders or window-punched plastic.
- Windowed ladder-line (WLL) is just that: 1-inch twin-lead with windows punched in it. Some call it window-line.
- The “true” ladder-line is best called “open-wire feed-line,” or simply open-line, to distinguish it from window-line. This is the type made from two parallel wires, separated by spreaders.
What to Get
Get the 16- or 14-gauge stranded window line from Cable-Xperts or Wireman. Don’t get that 18-gauge solid-wire stuff—it breaks when repeatedly flexed. Well—some people swear it lasts forever. I guess it will if you completely immobilize your connections.
Brew Your Own
The one problem with window line is that it tends to change characteristics when wet, and the longer the run, the more tinkering you’ll have to do with your tuner as the weather changes. The solution to make your own open-wire feeders. It isn’t hard or complicated.
- Get a 500-foot roll of #14 THHN or THWN insulated stranded (
$20~$45 at builder’s supply). Pick a color that blends with the background. Get some pressure-treated 4x4s, 12 feet long, and plant them in the ground every 50 feet or so. Many people do not use any poles; they just swag it from the tower to the eve of the house, and it works fine. Poles would be needed for runs over, say, 50 feet or so. It depends on what wire you use, how much ice you get, etc.
- For spreaders, all you need is some kind of small, UV-resistant, semi-rigid plastic pipe, like 3/8" PEX. Cut them 4 inches long, and make enough to put one every 4 feet in tensioned spans, and every 2 feet in slack spans. You can notch, or drill holes, in each end of each spreader then glue them in place with Silicone caulk or hot-melt glue. You can also purchase pre-made snap-on wire spreaders called Ladder-Snaps. I used Zareba Ribbed Tube insulators, which are made for electric high-tensile fencing, placing them between the wires and running a thin zip-tie through the middle (twice) and arounde the wires. (See my 80-Meter Doublet article).
- String up two strands of the wire, appropriate length, between trees. Pull them even. Install spreaders. You can make a 150-foot ladder line in a couple hours. It’s a good idea to continue the same wires on past the spreaders, to form the dipole. Then you have no solder connections to seal or break. Another thinkg you’ll need to have a 300-foot open-frame tape measure (~$20 at Harbor Freight).
- Congratulations - you just made modern, high-quality “true” open-wire ladder-line, and you didn’t even have to boil a bunch of wood dowels in paraffin!
- Now attach it to your supports with little electric fence insulators (on wood posts) or PVC pipe stand-offs (up the tower), as needed.
Note: Some say you have to use bare wire - baloney. Why mess with wind static, rain static, and corrosion? The same holds true for all wire antennas. Never use uninsulated wire. It just isn’t necessary. Of course, if you already have a bunch of it, feel free, and maybe spray paint it…
One more thing to consider: Bending ladder-line at sharp angles can cause problems on the higher bands. This is because the magnetic field around the line will interfere with itself at the bend. Or so say the books! I have never had any problems bending window line at 90-degree angles, and I’ve even fed a 2-meter beam with window line, bent 90 degrees 3 times, and it worked fine.
Could u make me a box with 3 450 ladder line connecter switchable to 1 coming in to one line coming to the window to the 450 ohm in the tuner let me know thank you.
HOA restrictions so an attic install is my only way…..saw two articles, by Cebik and NorCal about a 44′ doublet for 40 thru 10…it would fit perfect in my attic. Station is on the 2nd flr so feedline to doublet would be rather short, maybe 20 – 25′. Any advice/recommendation on short feedline length? Any safe legnth’s. Tuner is the Palstar HF Auto only unbalanced inputs. Sure would like to make this work….not a lot of choices. Thanks for your help. 73 Steve K3WKM
The plus of the 44′ Cebik antenna is that it is bi-lobed on several bands, not multi-lobed. The minus is that it is quite inefficient, and hard to tune, on 40, because it is under 3/8ths-wave long on 40.
I’d favor the idea some suggested, add 3.5′ hanging down on both ends to get 51′, which is a G5RV-Jr. If you can’t hang ends down, you can zig-zag the elements under your rafters. Also, use a good 1:1 current balun (not 4:1).
See also, http://www.w8ji.com/short_dipoles_and_problems.htm
That would be enough to steer me away from the 44…
Sorry, but I have no idea for a good LL length for a 44′. My suggestion is make a 51′ and use the LL length specified for a G5RV-Jr (16.5 feet). Then a 1:1 current balun, then a few feet of coax to your tuner. I think that will be better on 40, and easier to tune.
Thanks very much for the advice…..I’ll take a look at the attached links…I have a Balun design 1116 1:1 choke balun which should work nicely https://www.balundesigns.com/model-1116d-1-1-balun-optimized-for-low-bands-5kw/ I’ll let you know how I make out 73 Steve K3WKM
OK as advised I used 51′ center fed with 16′ of 450 Wireman window line to a 1:1 choke balun and 16 inches of 9913 to the back of a Palstar auto tuner. It works better than I could expect for an attic antenna, Palstar has no problem tuning and a few tries using the ATU in the Flex 6500 also worked well. First contact was Italy from my QTH in Philadelphia followed by Cayman Island and Bermuda….all on 40 meters. I tried a few other bands with no problem. Tnx for your advice 73 Steve
Hey that’s great! Glad it worked for you. Thanks for the feedback, now we have another empirical data point.
Thanks for a well written article. I hope you are willing to go a little further with your help since I am new to the art of radio.
I currently have a 150′ dipole fed with 300ohm window line (at least that’s what I called it before reading your article) running into an MFJ tuner.
First question; it sounds like you would recommend changing to a 450ohm feedline. Yes?
Second, you recommend adjusting your feedline length. Cutting wire is easy, but how do you recommend splicing additional feedline to extend? Are there acceptable clips that would allow me to quickly change the antenna wire i have attached to the balanced feed? Thank you for any help.
No, there’s no reason to favor 450 over 300. Indeed, W8JI (on the DX Engineering site) recommends 300 (½”) window line for doublets, as 300 is closer to the geometric mean of impedance swings than is 450.
I don’t like the SWR variations (at the tuner) when window line gets wet, so I use open-wire ladder-line, which in my case of #10 wire at 4″ is about 510 ohms.
But remember the characteristic impedance of any line is pretty meaningless when operated at high SWR, as the actual impedance varies low to high (then high to low) every quarter-wave.
This variable impedance along the line is why length matters, in a high SWR system. You don’t want a length (like a quarter or half-wave on 80) that presents a real low impedance to the tuner, and a real high impedance on the next higher band. Hence, the general “odd-eighths” rule.
For adding length, I’d just splice, solder, and weatherproof it (GB Liquid Electrical Tape, or silicone caulk). I never thought about using connectors to quickly add/remove sections, but I imagine one might use Anderson Powerpoles, or maybe a 240VAC Twistlock plug set. Both should work fine (grease the contacts, weatherproof, etc).
Oh! and another good way to splice wires is simply crimp and solder ring lugs, then use screws (8-32x½) to connect them. Easy to tape up after you’re happy with the length.
Dove posso trovare distanziatori a clip in uso al mondo agricolo/giardinaggio ?
In Italia se possibile.
I am new to antenna Building and I have been constructing a homebrew 450 Ohm Ladder line antenna(The antenna itself is made of 450 Ohm LL) and my question is does the Ladder Line have to be Vertical or Horizontal what I mean is the Spreaders Vertical or Horizontal or in your experience does it make any difference?
Sorry if this has been answered before.
Thank You and 73
It doesn’t matter. The horizontal runs can be flat or on edge. If you pull one wire a tiny bit tighter it will stay on edge (spreaders vertical); indeed, it’s harder to pull them exactly to make the line lay flat (horizontal spreaders). I run most of my line vertical as I think it helps water drain from the spreaders.
Sorry, really basic question here. I’ve made open wire line per your instructions. I first made a 14awg version, 4″ spreaders. That might be too heavy for portable use (will test it today). So I’m also making a version with 18awg stranded speaker wire, with 1″ spreaders every 6 inches (your site says that should give me 450 ohms, which sounds good to me). Even with spreaders only 6″ apart, there’s some variability in the 1″ distance between the two wires. It’s only exactly 1″ if the feedline is pulled taut. I constructed it to be exactly 1″, using a jig. That slight variation is normal, right? I’ve just never seen homebrewed ladder line in person, and can’t find pictures of what it looks like just hanging straight down vertically. Can’t thank you enough for this site. I’ve read this section on ladder line countless times, great information.
Hmmmm.. Yeah, I wouldn’t use speaker wire, it’s just too flexible, and as you say, would need to be pulled taut. And it’s likely to turn into a mess when rolled up.
Variations in wire spacing are not critical in 4″ line, but with 1″ line the acceptable spacing variation is much smaller—and not by ¼th, but by some cube root function, IIRC. This is why open line is usually 3-6 inches.
Your best choice, for convenience and handling in a portable situation, will be the 300 ohm ½-inch window line from DX Engineering or Wireman.
Some of that, and your dipole, could easily be rolled up on a plastic extension cord reel, which rolls it in straight without twisting it. Then you just need a 1:1 current choke/balun and a tuner (do NOT use a voltage balun or a 4:1).
Gotcha, makes sense. I tried out my new 14awg stranded doublet yesterday (66′ antenna, 40′ feedline with 4″ spreaders) and it worked great. Didn’t use the last section of the fishing pole, but that’s true for a number of portable antennas I use. I also built a 1:1 current balun, and used it. So I think I’m all set. Thanks for all the help. I’ll probably try putting that doublet up in my yard just to see how it does with my home station and 100w. As for winding the feedline, I found a trotline winder at Walmart for $3.67 that works great.
I just put up a horizontal loop using 14 gauge stranded copper wire. the loop is approximately 375 feet long. I have 28 foot 450 ohm ladder line feed line going into a 4:1 balum. My SWR on 80 meters is great on 40 meters at 7.185 it is 1:4 – 1:6. However when I move up to 7.251 SWR jumps to around 2:5 or higher. Any suggestions?
Change the length of you ladder line by 2-3 feet and see where the low point moves to. Then change it once more to move the low point to where you want it.
Or just use a tuner.
What will the impedance be of the brew your own feeder line?
Generally 500-600 ohms; it depends on the diameter of the conductors and the spacing between them. I use this calc – http://hamwaves.com/zc.circular/en/ – but it really doesn’t matter since L-L is usually used with high SWR on the line and a tuner in the shack. With standing waves, the impedance varies along the line (that’s what “standing wave” is) and it repeats every half-wave.
Am enjoying your web site once again. Thank you.
It would be great to see some radiation pattern charts showing a Multi-Band Doublet Antenna center-fed with Open Wire 600-Ohm Line, showing patterns for the various bands. Lots of possibilities and variables here, but surely there are some examples published somewhere. Hopefully there’s an example showing radiation patterns for a ‘typical’ 67′ foot long, center-fed doublet operating on 40/30/20/17/15, with 40′ height above average ground. Thank you.
You can model it and make nice 3D pattern graphs with MMANA-GAL. The basic version is free. See http://hamsoft.ca/pages/mmana-gal.php
hi im in new zealand i would like to build a quad 1.5 times normal size on all frequencies and im not sure if i should use lmr 400 …rg 213 .cann i use aldder linr 450 ohm .And can it be done or is it just for dipoles and grrv and the like
He built a gigantic multiband quad with ladder line feeds and 10 relays.
I’m trying to wrap my head around something.
On DX Engineering Website – Baluns: Choosing the correct balun.
From Table 1
3.5-30Mhz 110ft DiPl 30.9 (choose odd multiples of this length)
But 30.9×3 is 92.7
Does this mean 92.7ft LL will resonate at 5.3Mhz(60M)?
If so, why would they suggest this length?
At 110′, sounds like you’re talking about a G5RV, which needs a specific length of LL as a transmission-line transformer. Go with what DX Engineering says to use for a specific design, those are smart folks!
Though, I’d use ~125′ and a non-resonant length of LL, as in the article, and not mess with G5RV’s peculiarities. G5RV (Varney) never intended his design to be an all-bander, but a 20M 3/2.
I agree with the others – this is the best article I’ve ever read on open feedlines. I’m in the process of putting up a 700′ horizontal delta loop (roughly 21,000 ft2) and will be using homemade ladder line with a knife blade switch to ground (outside the house) when I am not using it, thanks to this article. Many thanks.
I have the space to do this as well…Probably also get a 700 foot loop, at about 35-40 feet average height above ground. Let us know how yours works
I have a rotatable dipole that I need to run bout 150 ft of wire. From what I have read I can use 450 ohm line from it. I will have to switch to coax to get into the house about 20ft or so. If this will work can I just twist and solder the ends? Are there any real down sides. There have not been many questions about using ladder line on factory antennas. Thanks
Yes you can connect ladder-line directly to a short run of coax. Might be better if you add some ferrite chokes to the coax, near the tuner.
I was looking at the low loss’s and thought it might do well for my RC Airplane antennas at about 50ft lengths. I read somewhere that 450 ohm ladder line would work well about 2 mtrs because the gap needs to be less than 1% of the wave length and at 1.2 Ghz that would be about a tenth of an inch or 2.5mm. Would common 2 conductor wire, like lamp wire work or is there some other issues with the balanced line at higher frequencies?
Ok, I read the next page and see you recommend the 1% rule as well. Any thought on my high freq. ‘Ladder Line’?
Years ago the ARRL labs did a test of 18-gauge lamp cord at HF and found the line impedance to be, if I remember, about 110 ohms, and it was quite lossy, due to dielectric heating of the continuous and relatively thick insulation. If it’s quite lossy at HF it will be terrible at UHF!
As far as I know (which isn’t very far!) parallel lines are used for UHF and microwave only on printed circuit boards; and modules are interconnected with very short teflon RG-174 or similar.
Another example is wi-fi hotspots — they run Ethernet with PoE and put the transmitter atop the pole, connected directly to the antenna, as any feed-line is too lossy.
I have an 80 meter Loop fed with 30 feet of coax twin lead made from rg58 coax,will I gain anything by replacing it with homebrew ladderline?
I don’t know. I’ve read that twin coax feed-line is very low-loss at high swr, and at only 30′ run I don’t think you’d see much if any difference. But I’ve never seen any actual comparisons. If you do switch to LL, please take some before & after measurements and post them back! You could pop some 4″ spreaders between your coaxes and feed the shields.
I have about 140 feet of doublet antenna (70 feet each side of center) and this comes into about 42 feet of home made ladder line, a 4:1 balun, and into the Kenwood TS850 auto tuner on a one foot co-ax.
With that setup, the lowest I could go was 7.183, and 3.974. I added more and more ladder line, and I can now tune almost to the bottom of 80 meters, plus quite a bit of 160 meters, and all the others. Now I have it draped all around the shrubbery.
My question is… I don’t have room for all the extra ladder line, it was just a tuning experiment, BUT will cutting some of the original length off get me into tuning range again, or will I just lose all the low bands?
Well, I’m sure you know, radio’s internal auto-tuners have a pretty narrow range.
Whether cutting your L-L shorter will bring it in range, at all desired frequencies, or not, is a seriously complex NMC problem, so you have to just try it and see. First remove the 4:1 balun and see what happens.
I don’t think you’ll get there with an internal radio autotuner. Those are typically meant to handle a 3:1 swr, the better external tuners handle 10:1 or more. Think of the impedance at the radio end varying in a sine wave as a function of the length of the L-L, at some given freq, then think of that being in-range of an internal autoutner at all HF bands! It’s complex.
If I’m brewing my own ladder line, is there any reason to not just continue the same wire for the dipole?
That’s the best way! No connections to corrode. W7FG makes & sells them like that, see trueladderline.com. He also has baluns, dacron line, marine-grade pulleys, etc.
I have a 350 foot each leg, Vee beam pointed to Europe – supported at 40 feet and did exactly that with Soft aluminum electric fence wire, bringing it down to a four inch spacer, then four inch spacers all the way back to a 15 KW DX Engineering 4:1 balun. Works well.
I wanted to say thank you for posting this! I have wanted to play with ladder line for a while, but when I mentioned it I heard so much misinformation. Following your article, and adopting a “screw it, we’ll just see what happens” approach. I am now running an inverted-v dipole operating from 80-10m with no problems whatsoever fed with 450 ohm window line. I absolutely love it! I have even had quite a bit of success running at outputs as low as 1 watt on 40 and 80 and getting 1,000 mile plus QSLs, and the band conditions are not great right now. Can’t wait for the peak of the next solar cycle!
Thank you again! K4RJD – Richard D.
Glad you liked the article.
Yeah, most hams just can’t believe how lossy coax is until they switch to ladder-line. But they sure do like to get on the air and spread misinformation and opinions. I’ve heard it all.
I love your straight forward info most can understand. Can I use 14/2 Romex as is for ladder line or will i have to split and separate it, since I have lots of it on hand. Or is the space between the two wires not enough insulation. New general ticket after am, sw and ham listening for many years. Thanks
Unless it’s very old Romex it’ll have a ground wire in the middle (i.e., 14/2 w/ground) and that wouldn’t work.
14/2 w/o ground would work but very poorly.
The insulation is OK for moderate power, but the wires are too close — you need a lot more air dielectric than plastic. The ARRL tested lamp cord many years ago; it had ~110 ohms impedance and was very lossy (much worse than coax), if I remember correctly.
Stripping out a long run of Romex would be difficult, and the solid conductors would break from wind flexing.
I suggest you either buy a roll of stranded THHN and make 3-4″ LL, or just buy 1″ windowed LL.
This is fantastic. Sometimes I see the same basic info. paraphrased endlessly but I logically form questions which someone like you comes along and answers with working examples which exceed the status quo. Thank you. I will now make the open wire feed I’ve been hesitating to do. It’s, even, mainly for a valve Halicrafters receiver meant for direct hookup this way. I’ve been doing the random wire with L-match, but would like to try a zeppelin or something (something I can transmit on, also, with up to 100 watts after I get my General ticket). I have the wire to make the feed line and elements, the extra air cap to turn the L-match to a T or Pi or something, and you just dissolved my inhibitions. Thanks! W4VEY Jeff Burris, FL