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

### Antenna Mythology

#### Resonance

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 many 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 ~12:1. 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 50Ω.

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 its characteristic impedance is closer to the geometric mean, so 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 geometric mean of the antenna's impedance range, from lowest (odd half-waves) to highest (even half-waves).

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 Losses

Another popular myth is that antenna tuners are very lossy and waste a bunch of power. Baloney! A T-tuner, properly used, is about 95% efficient, and a switched-L tuner (like most auto-tuners) is about 98% efficient. If your tuner is getting hot, you have something wrong in the antenna system, and are exceeding the design limits of the tuner. A T-tuner becomes quite lossy when the antenna side impedance is low (<50Ω), but when it’s high (>50Ω) the efficiency is over 90%, reaching about 95% at ~500Ω. (See the graph at this article by G3TXQ ).

On the other hand, baluns can be very lossy, 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 need to change the feed-line length (to move the anti-node out of the ham band), and use a balun designed for wide impedance variations.

Traditional baluns, such as the coax-wound toroidal 4:1 Guanella, are not designed to handle the extreme impedance variations of all-band doublets. They tend to arc or saturate and burn up at high power when presented with impedance extremes. Modern balun manufacturers have discovered this and now make 1:1 choke-baluns designed for ladder line feeds. Both DX Engineering and Balun Designs now make “tuner baluns” that are 1:1 current choke/baluns, and MFJ now puts 1:1 bifilar-wound choke/baluns in some models, like the 989D.

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 dipole. If the power in each conductor is equal and opposite, we have complete phase-cancellation, and therefore 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!” Again, ladder line should be balanced, and a good choke/blaun used at ot near the tuner. To further reduce common-mode current that may bring RF into the shack, 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 by induction from the antenna and re-radiate it into the shack. A non-resonant feed-line length will present a high impedance to common-mode current. And, as with any feed-line, it’s best to run it perpendicular to the antenna as far as possible 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.
4. “It’s too hard to bring into the shack!” Baloney. There are many waterproof ways to bring ladder-line into any shack. You can drill two small holes through the wall and bring two #12-#14 wires through, then caulk, and connect them to the balanced output of your tuner. Or better, mount your balun outside the wall and come in with a few feet of coax. I like that way better because the coax is easy to disconnect (at a bulkhead fitting) during storms.
5. “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 the line 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.

Continued…

1. Harold
Can I paint my ladder line with Exterior Latex
Paint to match my vinyl siding.

2. Harold,
I am planning on putting up a horizontal loop antenna mainly for MARS. I have seen a number of loops and designs and am in a bit of a quandary. Most of the designs tell you to install the loop with some sort of ladder line. I am planning on putting up a loop approx. 500′- 540′ long and I have open ladder line that I have already purchased. Would the length of the ladder line make a difference?
I have a Palstar Auto Tuner, can I run the open ladder line to a balun and come in the house with less than 10′ of coax? If so, what type of balun would you recommend? Your comments are appreciated very much!
Thank you,
Joe
W3OYJ

• Hodwy Joe, That should be great antenna!

Yes, the LL length should be around an odd-eighth wave multiple of the loop’s fundamental resonant frequency (see other comments below this one) to place the impedance extremes between bands. Then some trimming might be needed for an upper band to get it within the tuner’s range.

I haven’t used one (yet) but will recommend see: Balun Designs 1171 tuner balun. A coax jumper of 10 feet or so will be fine.

Please let us know how it all works out!
73, KV5R

3. Considering the excessive weight of a high-power 4:1 balun hanging in the air from the antenna wires, our club is considering feeding an OCFD with about 60 ft of 450 ohm ladder line terminated in a 4:1 balun at roof level, connected to 100 ft of 50 ohm coax to the shack. I am hearing mixed opinions about the wisdom of this approach and would appreciate some enlightened advice. A related question: I am advised that an OCFD is in fact a “balanced” antenna because the current and voltage are identical either side of the feed point. I would appreciate confirmation of this technical point in addition to the practical question posed above.
Many thanks
John VA7XB for Surrey ARC VE7SAR

• P.S. This antenna will only be used for 40 and 80 m.

• Hi John,
No, an OCFD is NOT balanced, and unless it has a current balun/choke at the feed-point, the feed-line will be a radiating part of the system.
Running 100 feet of coax from balun to shack will work on 80 but be terribly lossy on 40, assuming the dipole is cut for 80 meters.
To use for both 80 and 40 you will need to center-feed and run ladder line all the way, to a good 1:1 bifilar-wound choke/balun in or near the tuner (few feet of coax jumper is OK). If the doublet is cut for 80 (~130 feet), the impedance will be low on 80 (and a 4:1 would make it WAY too low), and very high on 40, where it’s 1 WL long.
The antenna I run now is a 130-foot center-fed dipole at 40 feet, with ~154 feet (5/8ths-wave @ 3.8MHz @ .95VF) of 4-inch open-wire ladder-line, to a 1:1 bifilar-wound choke in a 989D tuner. It works well on both 80 and 40 at 1kw. I designed it based on engineering documents from both DXE and Balun Designs. They recommend using ladder line length that is odd-eighth-wave multiples, so the line transforms low impedance up to medium (~500 ohms) on the fundamental frequency, and also transforms high impedance down to medium on the even harmonic (ie, 40M on an 80M dipole). Both DXE and Balun Designs are now making 1:1 choke/baluns designed to be efficient over a wide impedance range typically found in “all-band” (non-resonant) ladder-line-fed doublets.
73, –kv5r

• Hi Harold
Thank you for your quick and enlightened reply. I had a feeling that this was not going to work. I was probably hasty in stating that the antenna will only be used on 80 and 40, as it would be nice to have the WARC bands since our only other antenna is a 20-15-10 beam. With that in mind, I think the solution for us is to stick with the OCFD, with a less-heavy 4:1 balun at the 66/33 coax feed point, and with extra attention to adequate suspension of the balun. We had considered using the 10 kw balun from DXE, but now believe the 2 kw version would be OK even at full power and a modest mismatch.
If that doesn’t work, your suggestion of an 80-40 centre fed with ladder line or open wire feeder might be our second option, keeping in mind the odd quarter-wave length for the feed line. We could probably make that work.
It is obvious that an antenna like the centre fed dipole is “balanced” because of its symmetrical geometry, but it leaves me wondering …. if equal voltage and current at the feed point are not relevant, what are the defining factors that make an antenna “balanced”? I am guessing it is a symmetrical current and voltage distribution along each of the legs that is important perhaps??
73, John VA7XB

• Okay, some clarifications:

The classic center-fed 80 (or 160) meter doublet, with ladder line and a tuner, will work all HF bands, though some trimming of the line may be needed to get it within the tuner’s range on one or more upper bands. That has been my experience with both a 160 and an 80.

The line length recommended by DXE and Balun Designs is odd-eighth-wave multiples (1/8, 3/8, 5/8, etc., of the fundamental frequency), NOT odd-quarter. The formula given is 123/f(MHz) x VF x n(odd) = LL length. The general idea is to place impedance extremes between bands, at the tuner end of the line, so that the tuner never “sees” excessive current (like < 25 ohms, or excessive voltage (like > 3,000 ohms).

Not sure where “equal voltage and current at the feed point are not relevant” came from… A “balanced” doublet DOES present an equal and opposite load at the feed-point, thus 180 degree phase cancellation in the feed-line, so it’s a transmission line, not a radiator. Such balance at the feed-point is most easily provided by both geometric and near-field-environment symmetry (same length and height on each end; flat-top or inverted vee, but not a sloper, for example). Simply put, when each leg draws equal and opposite-polarity power, the transmission will not radiate. It has nothing to do with impedance (mis)matching or SWR, just balance and thus phase cancellation.

The idea of the OCFD is to hit a higher impedance feed-point (for parallel feeders), and I hear they “resonate” on all multiples, not just odd multiples (as does the full-wave loop). But the down-side is that the OCFD is highly UN-balanced (at the feed) and thus causes a lot of feed-line radiation, requiring some form of current balun/choke/isolator device at the feed-point. Such devices must handle high current on some bands, high voltage on others, without overheating, saturating, or arcing — so they tend to be beefy and expensive. And keep in mind, the more work a “BAL-UN” has to do, the more power it wastes as heat. Thus, if you use a light-duty balun on an OCFD at high power, you will quickly fry it.

For that reason, I avoid OCFD designs, and also because all the old antenna gurus recommend against their use except for low power.

The long-standing, tried-and-true, recommendation for the multi-band doublet is to center-feed with parallel feeders (window-line or open-wire-line), and use no balun except a common-mode choke (typically a bifilar-wound toroid at the shack end) and a big ol’ antenna tuner.

That arrangement (1) makes a great NVIS antenna on the low bands; (2) works reasonably well at lower angles on the higher bands where it’s > half-wave high; (3) eliminates the problem of coax’ high loss at high SWR; and (4) is simple to design and build.

The down-sides are (1) it requires a tuner and common-mode choke; (2) performance on the upper bands (particularly 10 meters) is rather spotty due to many lobes and nulls in the pattern; and (3) may require tweaking feed-line length to get the shack-end within range of the tuner on all bands.

Sorry for the long reply, but I just did all that research before putting up a new antenna a few weeks ago, so it’s fresh on the brain! 😉

73, –kv5r

• Harold
I am learning so much from this exchange. Thank you for correcting my careless reading of ¼ for 1/8 wavelength. Now … if we were to deploy a 130 ft centre-fed doublet fed by balanced feeder for multi-band use, the new challenge would be the need for a wide range tuner at the shack end. This 1 kw station will be used by a variety of club members having different skill levels and the potential for a fatal mismatch is a significant risk.
Your comments are leading me to think that our simplest solution would be to have separate resonant 40 and 80 dipoles, each with a 1:1 current balun at the feedpoint, fed by coax – not easy, but certainly possible. There would be no WARC band coverage, but that is a lower priority as we primarily use the station for contesting and training purposes.
BTW, years ago I used a “multi-band” 100 ft. long dipole fed with open-wire feeder connected to a 1:1 choke balun fed by coax and an “Ultimate Transmatch” at the shack, but the swr on the coax on some bands was off-scale giving me serious RFI issues.
Harold, thank you for sharing your expertise and time to help us understand and work towards a solution that fits our need. Do you have any objections if we publish this exchange in our club newsletter? I view it as a learning opportunity not only for me but for our members.
73, John VA7XB

4. Harold
I am going to put a Cobra ultra lite in the back yard
on a fiberglass pole. Can I run the ladder line along my
fence witch is PVC without a stand off.

• Hi,
PVC has a pretty high dielectric constant and will probably cause some line loss. You’ll just have to try it and see if it’s enough to matter. For ladder line to work best, it should be surrounded be several inches of air.
73, –kv5r

5. Great info here, thanks!

1 – regarding routing of ladder line away from the feed point @ 90 degrees, is straight down preferred over out and away (sloping) or would it matter so long as balance and symmetry are maintained?

2 – OK to run ladder line inside fiberglass mast to keep it out of the weather or does this affect losses, velocity factor?

3 – OK to splice ladder line to true open wire line?

Thanks -Jim

• Hello Jim,

1. There should be a phase cancellation null perpendicular to the dipole, all the way around it, so I don’t think it matters if the line is vertical, horizontal, or even swagging from vertical to horizontal, as long as it is in that perpendicular plane. And if it’s not, no matter, your balun should choke off most common-mode current. So that perpendicular thing is optimal, but not essential.

2. Running ladder line inside a fiberglass mast will increase losses a little bit, as the fiberglass will put a dielectric in the line’s magnetic field. I have no idea how much it might be; it’ll depend on the thickness, diameter, and length of the mast; frequency; dielectric constant of fiberglass, etc. If you’re considering it just to keep the LL dry, well, consider that the mast will have a lot more surface area than the LL’s web, and encircle the line, so when wet may be worse than wet LL.

3. Yes, you can splice window line to open line. There’ll be an impedance bump from 600 to 400 but I don’t think it will matter.

Please let us know how the fiberglass mast thing works out.

73, –kv5r

6. Harold: Thank you for your input. I was afraid you were going to say what you did (hi..hi..) Based on your response, I think I will leave the system as is.

FYI: There was one more thing I did to eliminate some coax and that is feeding 2 diff wire antennas (a modified fan) with 1 coax line coming down the tower.

HERE IS WHAT I FOUND THAT WORKED for me: [NOTE: My property has 5ft fencing that allows me to place 7 ft high supports for the antenna wires around the property.]

*I made up several Plexiglas plates (5×5″ by 1/4″) and this allows me to mount a ferrite current balun (1:1) on the plate. In addition to the coax line, I also bring the 2 antenna wires (separated by 5″ at the top) down together and they go to the same location at the fence. From this location, I separate the wires (I make a horizontal fan from the center point) so that there is a 5 foot separation at the fence. **I found that I can trim each wire for the band and achieve a flat SWR at the center freq for each band (except 80 & 160M tuner needed). **Note: All the wires that come down to ground are separated at the top by 5″ and at the bottom by 5 feet (at the 7 ft high ground level). >NO WIRES ARE CLOSER THAN 5 FT TO EACH OTHER AT THE FENCE< **All IN-V's are broadside to Europe and the Pacific. So far this system has went through a rough PA winter with little effects to the operation of each band.

40/80 together….60/160 together…..30M works better alone

Thanks again….Bob W3BTX

7. Harold: NEED YOU HELP.

SOME BACKGROUND: I now live in the city (on a small lot) with a 50ft Rohn tower. I have an M2 XR5 beam at the top (around 57ft) and have a long side arm (at 48ft) that sticks out 3ft on each side of the Rohn tower. Both sides of the arms have several pulleys that allows all wire antennas to be pulled up and positioned from ground level. >ALL WIRE ANTS ARE USED AS INVERTED V”S BECAUSE OF JUST 1 SUPPORT (the tower)<

NOTE: I have managed to get all wire antennas (30/40/60/80/160M) resonent and just use an MFJ Mo 998 auto tuner on 80 / 160 to cover the entire bands. *All coax runs down the tower (45-50ft) to an MFJ switch then about 100ft of good coax to the tuner in the shack. I realize there is loss, but surprisingly the system works very well on rcv & transmit with my downsized situation.

MY QUESTION: I am wondering what to expect if I were to replace all the wire antennas (except 160) with a single IN-V using 600 ohm feed line dropping down (3 feet away from the tower) that would connect to a 4:1 5kw balun. Then using a short run of coax to the switch and around 100ft to the tuner. **I picked up an 80meter dipole with 50 foot of 6" feeder from WB2JIX and would use this antenna if YOU THINK it will work as explained. **It's possible to add some feeder line and eliminate all the coax to the house (except for a short run to the tuner) but that would involve a lot more mechanical problems.(More things to go wrong)

Thanks in advance for you thoughts on if this will work?

• Howdy Bob,
In your current situation you have 60-40-30 as resonant antennas with very low losses, and 160 & 80 with moderate SWR-related coax losses on high & low ends of the bands.

If you change to an 80-meter dipole for 80-30 you will have very high SWR on the line on 40 (voltage node feedpoint) and just running ladder line down the tower, then retaining 100 feet of coax, will be bad losses, both in the balun and in the remaining coax. Not worth the change; you’ll be disappointed.

Running ladder line all the way is the only way to (nearly) eliminate those losses, but since you already have 5 resonant antennas, that also isn’t worth the change — unless you just need to reduce sky clutter.

What I would suggest is either:
1) keep what you have, or
2) feed the 160 with ladder line, all the way, to a Balun Designs Model 1171 1:1 ATU balun at the shack, short jumper to tuner. (see http://www.balundesigns.com/model-1171-1-1-atu-current-balun-1-54-mhz-5kw/ ). That one’s made for very wide impedance range (high SWR) found in non-res multiband dipoles with LL.

73, –KV5R

8. Hi Harold, thanks for a very informative article on LL.
I use a 1/2 wavelength doublet on 40 m for portable work. I am currently using 300 ohm TV line and I am looking to replace it with window line.
I use this antenna on all bands from 40 to 10 inc warc bands, with atu, with good success.
I am using approx 10 m of feedline (30′) , is this a good length for this antenna and the intended band usage?
Thanks.

• No. That’s too close to a quarter wave on 7. Go to ~40 feet. That will put your min/max impedance excursions between bands so that in-band the tuner will not see such lows or highs.
73, –kv5r

9. Dear Sir,

Thank you very much for the web page on antennae. I am contacting you because I would like to ask if you kindly could help me with the following. I am a new ham radio hobbyist and trying to build a wire antenna that I will install at my house roof in an inverted vee form. The antenna is called G5RV which is multi band. For tuning this antenna I have an instrument that gives swr vs frequency. I would like to calculate from this results the impedance of the antenna but I am not sure if this is possible nor how to do it. Using Smith Chart?
Appreciate very much if you can comment on this issue and any hints you could tell me.
Thank you very much in advance.
Kind regards,
Jaime Gordon
73 from 4X5JG

• Hi,
The G5RV is a non-resonant design except on 20 meters and its impedance will be all over the place in different bands. You don’t need to worry about its impedance, just build it to Varney’s design and then run it with an antenna tuner.
73, –kv5r

I hope it will not take me too much time to start installation.
I am buying all the components.

Kind regards,
73
4X5JG

10. Can I cross a balanced line of 450 ohm or 600 ohm through an aluminum window, closing it on the wires without risk of unbalance, change of impedance or radiate?

How do I get 2 balanced lines by the same window without interacting?
How to change balanced line easily? Remote switch for Ladder-Line?
I am 100% QRP.

Thanks!

• Yes, you cab cross a metal edge, perpendicularly, with ladder-line without any noticeable effects. Just take care the window frame doesn’t abrade the wire’s insulation.

In effect, there will be a low-impedance “bump” there, but at such a tiny fraction of a quarter-wavelength, it doesn’t matter. The bump may cause reflections and raise the SWR a bit.

The better way is the little board trick, where you make a 1×2 for the window to close on, and go through the board. The board’s edges are wrapped with foam weatherstripping; the window jammed down on it with a pair of parting-stops (little pieces of molding cut to fit between the top of the slider and the top of the window frame), and the gap between the slider and the upper pane sealed with weatherstripping. Not pretty, but a good temp setup for renters, etc.

You can remotely switch ladder-line with a DPDT relay. The regular 10A 240V Omron, with screw terminals, ~\$10-15 from Mouser, should be fine for QRP. At high power, RF-rated relays would be needed (big contact gaps to control arc-over).

73, –kv5r

• Thank you for that answer.

Here I have casement windows. So it’s impossible to use this trick.

Either I use coaxial cable (but I will not be multi-band) or I use a 4: 1 balun at the input and I pass through the window 2 cables (less than 20′). Or that I use 2 baluns 4:1 connect on a coaxial antenna selector to the radio.

On the other hand, I would have liked to maximize my QRP power by using the balanced line as much as possible.

Do you have a detailed plan to remotely control the relays?
Can the relays operate at low voltage and be powered by the balanced line?

I want to install a ”Skyloop” and a ‘Vertical Dipole ”. I think using the line of 600 ohms (maybe 450 ohm – undecided) for the ”Skyloop” and 450 ohm for the vertical of 2 x 20′(or 2 x 22’) allowing to cover from 6m to 20m (40m).

What do you think?

• You can pass through a wood or vinyl window frame, or wall, with 2 small holes, space same as ladder-line; needs a special drillbit (small but extra long). Use 2 brass all-thread rods (10-32), with double-nuts inside and outside. Solder ring-lugs on ladder-line. Seal outside with silicone caulk.

Remote relay — use 12VDC coil DPDT relay, run small wire out to it (#18 zip cord). I doubt there’s a way to use the L-L for relay power as you’d need DC blocking capacitors at the tuner, and at at the loop antenna (else, DC short). And who knows what 4 capacitors would do ti your SWR…

Put relay in a small plastic weatherproof box (PVC, not polyethylene, sun would destroy it); 3 pairs of brass screws (10-32), 1 in 2 out, etc. Run coltrol wire thru a hole and seal all connections with silicone caulk.

Sounds like too much trouble to me. Buy a 6M vertical and put it on the roof, run coax. Put up skyloop, as large and as high as possible, run ladder-line all the way in (as above) to a tuner with internal balun (balanced output).

That would be about as good as you could do, without getting into really expensive stuff like tower and beam, etc.

73, –kv5r

11. I am hanging K1JEK’s Cobra Ultralite ladder line center fed doublet 140′ long. I need your advice as I have at least 3 options to fit into my property limits.

I now have my rope and pulleys up at tree top around 80’ and I have to decide the best way to deal with the ladder-feedline. If I slope the feedline to my house entry point, the 450 ohm feedline length will need to be about 100-110’ which should keep it non-resonant for any HF bands. I can have a 4:1 current balun at the house entry and then it would be about a 20’ coax run to my tuner.
However, I have read that keeping the feedline vertical and perpendicular to the dipole is extremely important for efficiency and avoiding common mode induction. If I slope it to my house then it will not be 90 degrees with respect to the dipole but only 45 degrees making it much closer to one leg of the Ultralite than the opposite end.

So my second option would be to keep the feedline almost completely vertical for the 80’ height and then run it horizontal about another 80’ along the top of a wood post fence with 6” standoffs about 5’ from the ground. The fence is covered with a metal mesh but I figure the 6″ standoffs should be OK?? However this scenario uses about 160′ of ladder and I think this brings me to a ladder line length that becomes a multiple of some of the HF frequencies.

My third option, is to put the balun at the bottom of the 80’ feedline and use about 80’ coax to the house but I figure there will be a lot of coax loss with that long a run at high SWR.

Any advice would be greatly appreciated.

73 Jerry NY2KW

• Hi Jerry,
Well, all that stuff people (including me) write about keeping LL perpendicular is the optimal “do it if you can,” “theoretical best” -type-stuff.

I’d do the first way, your 110′ swagged at 45°. I don’t think you’ll have any problem. If you do get RF in the shack (re-radiating from your coax shield), put a stacked ferrite choke on the coax.

You could also use the 2nd option; I’d go more than 6″ above the fence though; perhaps 12-18″. You could clamp ~18″ PVC pipes to a few fence posts and attach the LL to them.

Definitely don’t do the 3rd option, long run of coax after the balun. Way too lossy.

My first 160M dipole was like: LL down 20′, then ~75′ horizontal, parallel to, 20′ under, one leg of the dipole, last 15′ was direct-connected RG-8 (no balun), and it worked fine (at 100W; might not work at 1500 w/o a coax choke).

Let us know how it works out for you!

73, –kv5r

• Thanks, that’s reassuring. With option one- I guess the ladder will “drape” down and I could get a lot of it hanging down almost vertical before it bends towards the house. With my k1jek doublet type of dipole is there any minimum length of ladder that should be hanging down vertical?

• The elevation angle (V-H) of the feed-line doesn’t matter (for horizontal dipoles). All that matters is that as much as possible be perpendicular to the dipole. Whether your slack is pulled straight down (V), straight out (H), or any angle between, even gently swagged from V to H, looking at it from the top (polar view), perpendicular is best — but it’s still gonna work fine if it ain’t.

Non-perpendicularity (if that’s a word) in the near magnetic field of the dipole, will induce some common-mode current on the line, but since the line is un-grounded this common-mode just bounces back and forth, unbalancing the currents on the dipole halves. Why?

Imagine an instantaneous moment when the opposite dipole halves are emitting North and South magnetic fields, well, you can see they will cancel, so there will be a “null” along the line perpendicular to the dipole. And as we move forward in time, all along the sine wave, the 2 fields are always 180° out of phase, so there’s always that null along the perpendicular line — a good place for a feed-line to be. How far?

If I remember correctly, the RF field decreases by the the inverse square of the distance — but the magnetic field (the so-called near-field) decreases by the the inverse CUBE of the distance — i.e., that sucker falls off really fast! Like, in 20-30 feet you can forget about it (well, unless you’re running some kW).

I suggest that all hams should have to study some basic AC theory, like electromagnetic induction, then stuff like antennas, feed-lines, and coils get a whole lot easier to understand. Well, the math is a nightmare, but the principles are easy to visualize.

73, –kv5r

12. Can a dipole be somewhat asymmetrically? that is,

I have enough run for a ~70 foot dipole/double (?) but wish to cover 80 m band to 10m, which from a seller, offers 125 foot dipole with 50 feet of ladder line feed. Can i form another leg of dipole as an “L” shape? so when view from above it would apper as “L”?

• Yes you can bend the ends of a dipole, either horizontally, or ends hanging down vertically. It would be best to bend both ends the same angle and length, to keep the load balanced. If you put all the excess on one end it’ll be unbalanced load and the ladder-line will radiate.

13. I have to run the ladder line from the back yard, along the house to the shack. I also have a couple of other coax fed antennas back there as well. Is it ok to run the ladder line next to the coax (even zip tied together)?

• No. Ladder-line is surrounded my an RF magnetic field (out to a few inches) and must be kept (a few inches) away from all conductive materials. The minimum separation is typically 4 times the line width.

14. Thank you for a great web site, its very helpfull to new hams like me. I’m building a 80-10 meter doublet ant. 60′ high, 135′ long, using 12 gauge insulated copper stranded, one cont.wire with the “true ladder line” 1 3/4″ between wires, plastic spreaders, 450 ohms to a 1:1 balun, to 55′ of LMR-400 coax down to the MFJ-941E tuner & radio. In my research I am unclear on how long (or short) the matching section of ladder line must be. The distance from the center fed ant. insulator to the balun on the roof is 35′ give or take, too much longer and it will be laying on the roof etc. Again I’m not sure about the VF, maybe 90? Or the length. Thanks for the help! Gary KD2IBQ

• Well I’d just run the ladder line all the way to the tuner. That 55′ of coax is gonna be very lossy on bands where the swr is high.

• I wish I could, but the LMR 400 coax would go through a steel pipe from the attic to the basement which will not work for the ladder line….not able to run it on the outside of the house (landlord) or drill through the walls, floors etc…
no other way to really do it other then to move the whole shack to the 4 1/2′ high, too hot in the summer & too cold in the winter Attic….

Thank you very much. Clarified ALL my doubts and learned a lot.

16. Hello,

I want to put delta loop antenna on the roof of the house. I just can’t decide which is better with leadder line or without ladder line.
Ea antenne 7b delta loop vs m0plk with ladder line?

Thank you very much
best regards
Ales

• Ladder line (and a tuner) is frequency-agile so you don’t have to worry about SWR losses in the feed-line.
If you’re building it and tuning to resonance on one frequency, then coax is fine.

17. Hi, this is a super resource, and thanks for all the q&a. I am a lapsed ham and am now working to get a new license, and also in the process of building a new house, and want to try and make it antenna friendly. The shack willl have to be on the first floor, but in the front of house, and my wife won’t let run ladder line out the front window to the second story roof. I can spec out internal conduit and wiring though. I will have multiple coax lines going to the roof.

I dont suppose it’s a good idea to try and run the ladder in a pvc conduit up inside the house where it would run parallel to the coax I suppose? I can put a remote auto tuner up on the roof though to fed a center fed dipole. Is it possible to configure the dipole with relays to be one of 2 end fed Zepps or the dipole? Would that be useful at all in terms of getting various forms of directionality?

Also, I do have a large tree on the lot, 75 ft or so. I could put a remote tuner at the base of it and run ladder line to to the top and fed an inverted vee. Do you think that’s a better approach than trying to deal with the roof?

Also, what is the best (preferably remote) autotuner that can feed a balanced antenna? I don’t see many that have balanced outputs. I could put a balun on the end to feed the ladder line, but which ones would you recommend for a beginner, both the tuner and balun?

Thanks very much!
Mike

• Hi,
Yes, you could put in a PVC conduit for ladder line but use the 1-1/2 or 2″ thin-wall PVC sewer pipe, not the gray conduit (too much dielectric loss), and be sure it is several inches away from all metal (wiring, ducts, etc.) up through the frame of the house. On the roof you can put two long-radius elbows; don’t glue them; to make an upside-down “J” on top to keep rain out.
But much better would be good coax (9913 or LMR-400) to a remote autotuner, as you say. Putting at the base of a large tree, then a good current balun, then ladder line up to a big dipole, would probably work very well. You’ll need some stand-offs up the tree so plan on a man-lift or bucket truck for that part. Try to make the dipole ~130-260 feet long if possible. In my experience, a large-aperture antenna works very well on the lower bands.
Using relays for multiples: RF relays are quite expensive, and you’re not gonna see significant directivity from a Zepp until it’s like 4+ waves long.
I can’t recommend particular baluns or remote tuners because I haven’t used them. You might look up some of the popular ones then read the user-reviews for each on eham.net, that’s what I’d do.
73, –kv5r

18. Question? I am installing a MFJ998rt to a 4:1 balun to a remotely tuned 80 meter horizontal Loop fed with ladder line from the balun. How can i lightning/static build up protect the tuner from damage???

The tuner is very expensive and i want to protect the station and tuner system????

Suggestions😳

• The 998RT’s manual should cover lightening protection and grounding; if not, contact an MFJ engineer. That’s what I’d recommend.
And you should run coax, not ladder-line, to the tuner.

• How about running 450 ohm ladder line in plastic electrical conduit under the house for a distance of about 50’…..no metal close to conduit. Can that be done? What about running in the same conduit with coax? Any advantage in running part coax to ladder line like a G5RV?

• Don’t.
Ladder line is for open-air suspension — running in plastic conduit underground will have ground induction losses.

• I am running heliax coax to tuner due 130 ft run.

MFJ says it has lightning suppression installed in tuner. I am going to ground it well and add an additional suppressor between tuner and balun.

This should take care of my concerns. Thanks for reply

20. Thanks for your terrific post. After reading it the and the comments, I have altered my design for a 160 meter square loop antenna thusly:

The ladder wire will the feed the loop at one corner via a mast on my roof. The mast is a 10 foot sch80 PVC conduit. The loop is secured directly to the PVC and the ladder wire will drop down the center of the PVC into the shack.

If you see a problem with this please let me know.

21. Hi
Would appreciate your help and thoughts on a problem I have encountered with my Doublet installed yesterday
The Dipole is 130ft long
I have 600ohm ladder line which has been cut to 36ft
my problem is I have an excess of about 16ft of ladder line
which currently sits on top of the roof of my house,Im aware it
needs to be kept away from objects
Will it effect the Antenna if I cut off the 16ft of ladder line
or can I roll up the ladder line
My shack is in a first floor bedroom and have little room for the ladder line to be in free space.
Brian
73s G0 DKZ

• I’ve used LL for years and found that a “heap” or haphazardly spread out excess LL won’t cause a problem. If you coil it up tightly, it does, it acts as a bit of a choke.

22. I use a 130′ doublet in an inverted V configuration Center is 57′ high. It’s 12 gauge wire and I’m using 450 Ohm ladder line (the heavy duty stuff). The ladder line is 173 feet long which goes to a 4:1 balun mounted on the outside wall of my shack, then a 3′ coax jumper through the wall to my tuner. Anyway, I have noticed that this antenna tunes well (flat) across the 160 band. Any thoughts about working 160 with this antenna? I’m thinking the long run on ladder line is acting as part of the antenna. Are there any problems that could occur by transmitting down there.

• The ladder line isn’t acting as part of the antenna if the dipole is balanced (center-fed).
If your 80m dipole will tune on 160, it will work ok but the efficiency will be quite a bit lower than a half-wave dipole (~260′). Your balun and tuner will also soak up a good bit of power with that much mismatch on the output.

23. 20 years ago,before I went QRT, I was a member of MARS, and they recommended a balanced doublet for general use. One of the comments about ladder line was that the way to keep the feedline from radiating was to ensure that the two legs had the same current. Someone designed a tuner with the balun on the INPUT and a method to individually adjust the impedance of each leg using two roller inductors, and two RF ammeters to fine-tune the adjustment.

With that in mind, I was thinking about feeding two automatic tuners with a balun, with the “single wire” output of each one feeding the ladder line. Any difference in impedance between the two legs would be automatically adjusted. I think.

Thoughts?

Tim, N7LRU

• I don’t think it’d gain you anything. The autotuner is a reversible L-tuner, with losses under 5%. The manual balanced-line tuner with 2 roller inductors may be a tiny bit better, but at a whopping cost.

• The problem we’re trying to solve is that at many frequencies outside of the ham bands (MARS, CAP, etc.) the balun feeding the transmission line becomes saturated (right word?) and overheats. I’ve had one melt and short, using only 150 watts. If you put the balun on the INPUT side of the tuner, it never sees a high SWR and, as you have said, open-wire feedline doesn’t care. What I said about balancing the phase was just to keep the feedline from radiating (to minimize RFI). Using a pair of autotuners was my idea, because I’m lazy HI HI.

• My MFJ-993 autotuner uses an internal current balun (2-core) and tunes a ladder-line fed dipole to any frequency from 1.8-30 MHz. At ~120 watts I never noticed any unusual warmth of the case.
Donno why your balun burned up at only 150 watts; suggest you try a better balun, maybe something like a DX Engeneering 2.5k. (I’m no expert on baluns!)
You could perhaps use an outdoor autotuner (SGC) at the feedpoint and just run good coax to it — that works well, tho you do need a pole at the feedpoint to support the tuner.
73, –kv5r

• Balun saturation is a common problem at non-resonant frequencies well outside of the ham bands. The SWR is astronomical, and most baluns can’t handle it, unless you use reduced power with a 2kw-rated balun. If you want to run legal power in that circumstance, the choice is to either buy or build a HUGE balun, erect a second antenna, or build a balanced tuner. A real conundrum. Since I also plan on erecting a large horizontal loop for 160m (ham) and 120m (MARS), the balanced tuner is probably my best bet. Both are relatively close to the ground, to maximize the skywave elevation angle for local message traffic communications (NVIS). With such high SWR, balanced line is the only solution to minimize feedline loss.

I’ve sometimes thought about designing a push-pull linear amplifier with a balanced output, to eliminate the need for a tuner. A pair of 4-400A or 833 tubes from a retired AM Broadcast transmitter would probably work.

24. I have been reading about 600ohm ladder line for quite some time and decided to go with it. I purchased a 160 meter 600oh, fed doublet from True Ladderline. Brian has been very helpful. I was having issues with my tuner, but long story short I ended up cutting the 600ohm
Ladderline down to 60′. I have about 80′ of rg213 coming in from the 4:1 balun/common core choke to the shack. Choke was put inline to keep out ref on 20,17 meter and up freq.
What issues is there or are there using the 80′ of rg213?
I get very good signal reports, better that when i was using a 160/80 meter fan dipole.
Thanks
DJ
VA3KBC

• Only issue is coax loss at high swr. You can bypass tuner and check swr (at very low power) across each band, then use the coax loss calculator to see how much loss the 80′ is causing at each freq and swr.
73, –kv5r

25. Hi there, thank you for publishing all of this great info and actually taking the time to address so many comments and questions (including the negative ones) you are a true Jedi. Anyway, I’m planning to take/pass the general exam in a little under a month so I am trying to plan ahead and get an antenna up that will put me on some of the HF bands I’ve previously not had access to. I’m primarily aiming for 20 and 40 meters and have been recommended by some local elmers to build a G5RV. Due to small residential footprint, I have been considering building the half-size version, but after reading your blog above, I am starting to have some other thoughts.

Let’s say I have enough room to build a dipole of around 50-60 feet end to end. I have already purchased and received 32 feet of 450 ohm ladder line. My tuner is a Diawa CNW419 solid state manual tuner and my radio is an Icom IC-701. Should I just build a dipole (Of whatever length i have room for) and feed that all the way to my tuner with the 450 ohm ladder line or should I go more off of published measurements for the half-size G5RV?

After reading your info on ladder line, I’m starting to believe I shouldn’t use coaxial cable at all if I’m dealing with a center fed dipole and that the dipole length doesn’t matter much as long as it’s at least a half wavelength of the lowest band I intend to use it on. As mentioned previously, that would be around 7mhz which would imply ~66 feet end to end.

Sorry my reply is so long but I look forward to any input.
73. -KG7WPQ

• Yes to the latter point; put up as much wire as you can, feed it all the way with ladder line. That will work better than a half-size G5RV.
If you have the extra supports and can bend the ends to get up ~125 feet of wire (in a Z or C or zig-zag shape) that’ll work 75M OK, too.
73, –kv5r

• As always, I’m finding that the satisfaction of an answered question brings more questions. I’ve calculated the feed point impedance of the theoretical antenna I plan to build as being around 72 ohms, and I am planning to feed that to my tuner with a 450 ohm ladder line that analyzer data from a local elmer has shown to be more like 390 ohms. Should I try to construct some sort of coupling transformer at the antenna feed point to match impedance between the antenna and the feed line? Obviously, feed point impedance is going to vary from one band to the next. My concern is possibly not being able to match to 50 ohms at my ATU. From my previous post, I’m aiming squarely at being able to use this antenna for 20 and 40 meters. I have looked at a schematic for my tuner (Diawa CNW419) and it does not appear to have an internal balun, nor does it have a twin lead connection point. I’m just trying to get a full idea of what I am going to need to accomplish to make this system work without causing damage to my radio.

73. -KG7WPQ

• You don’t need any matching at the feed-point. You will need a good dual-core current balun near the tuner.
I read a few reviews on eham.net on the -419 and they all say it has a very wide range and will tune anything, so you shouldn’t have any problem matching to the radio.
You really don’t need to engineer a non-resonant dipole on ladder-line. Just put up ≥½λ @ lowest freq, run ladder-line to a current balun and tuner — done!
73, –kv5r

26. Hi and thanks for a great blogg site, Harold (Y)

I really got a challenging QTH in Norway and today I use about 140m (459ft) of RG213 from my shack to a corner fed delta loop with a 4:1 balun way up a steep hill side.

Works great as a multi band from 80-10m and the swr is pretty good on all bands!
Because the long length I was thinking of give it a try with a 450ohm LL to get as much power to the antenna as possible to increase my tx.
I use a TS480SAT with Acom 1010.
The one positive thing about having the loop far away from the shack & the surroundings is I got no QRM at all.

What is the best way to do this?
– Go direct to the loops feed point with the LL without a balun?
– Use of balun outside between LL and shack?
– Need about 15 ft of coax between TX and outside connect, OK?
– Is 459 ft of LL usable in length to avoid RF?
– Because of the long length the LL needs to go through some tree tops, resting – is that OK?

73,
Frank
LA4GPA

• Hello Frank!
WOW, 459 feet of coax! Your SWR is low because you are losing most of your power in the coax.

Here’s what I’d do in you case:
Use #10 (2.6mm) stranded insulated wire, make 4″ (10cm) open-wire ladder line. (459 feet of windowed ribbon will be too lossy when wet). Connect directly to loop. Plant poles every 50-75 feet, zig-zag the path as needed to miss trees. Use electric fence insulator tubes as spreaders, every 5-10 feet. Connect shack end to 9:1 current balun, then short coax to tuner.
You’ll be amazed how much more signal you get. Please let us know how it goes!

73, –kv5r

27. I can run the 450 ohm ladder line to the window of my house fine, but at the window I need to connect the 450 ohm latter line to RG 213 coax to run inside of my house to may radio. The length of the RG213 coax will be about 35 feet… To do this, should I use a 4 to 1 balun at the window where the 450 ohm line will connect to the RG213… I then will connect the RG213 to a tuner…. Will all of this work, or should I just do something different… The antenna will be a 130 feet long dipole connected in the center at about 25 to 30 feet high…. I would love to hear your thoughts on this…. Will the RG213 at a length of 35 feet kill the signal or even work at all doing it this way..???? Very best of 73’s… Claude WB4WHH Located in VA.

• Yes, that’ll work, but on the bands with high swr (say, 10:1) your 35 feet of RG213 will lose 17% at 7MHz, 23% at 14, and 31% at 28.5, according to the coax loss calculator. And to go from 450-50 ohm lines you need a 9:1 balun, not 4:1. If you go that route make sure to get a well-engineered dual-core current balun.

• Thank you…!!!!!!!!!…
I sincerely appreciate your answer….. You have an “Excellent” site…. Very best of 73’s….

28. Hi all,

I’m using the G5RV and am very happy with it.
However, why are you all using cheap and rubbish coax with it?
RG8/58/213 are very poor and do have big losses when SWR isn’t 1:1.
I’m using Aircell7 and at the ladder to coax connection I use 1.5m of ferrite clamps.
By doing so the coax can’t radiate and the losses are very low.
Also the velocity factor of Aricell7 and better coax is 83% instead of 66% for RG8/58/213. On top of that, Aircell7 has just 75pF/m compared to well over 105pF for the others.
When comparing these numbers, you notice that this coax is closer to the working of 70~90Ohm coax and as such the losses by bad SWR are far less.
Maybe something to think about, it works for me and many others.
Also last remark, please keep the ladder free of anything and put the G5RV as horizontal as possible for the best results.

BTW Aircell7 is cheaper then 213 and can handle the same power, yet being just 7mm and very easy to bend into small corners.

73’s Bas.

• Who said we are all using cheap rubbish coax? And Aircell is about the same as 9913 and LMR400. And extending the ladder line all the way to indoor auto-tuner is better than them all.
And all modern coaxes are foam PE which is .83-.85 VF, only the OLD you-can’t-find-it 213 is still solid PE .66 — which, BTW, is still great for low-swr feeds, and crap! it’ll hold like 13kv and makes good hv jumpers.
I don’t like Aircell because it tends to collapse internally if you bend it too sharp (whix all foam-pe coaxes will eventually). Actually, #10/2 Romex makes a decent feed if you can lowloss match it 🙂

29. I have 600 ohm open ladder line coming from trueladderline.com. My pole is 35 feet. About 20 feet the ladder line will be next to the pole. When you say double the width of the line away from the pole, is that the diameter of the line or the width of 6 inches meaning 12 inches? I was also told that if you twist the line every 3 feet it would keep it balenced due to being to close to an object. Any help would be appreciated.

thanks n5cwf

• Yes, if your ladder line is 6″ wide it should be kept 12-18″ away from metal tower or pole. If both sides of the open line are same distance from pole, you don’t need to twist it. According to the info on trueladderline.com, the spacing is 3.5″ so I’d go at least 3x that for spacing away from a pole. But ask W7FG, he’s the one with decades of experience with open line!

30. Will ladder line improve the performance of a balanced folded dipole? I’m running a balanced Folded Dipole that see’s 50 ohms from 2-30MHz. I know its lossy as heck and I’m feeding it with approx 40ft of RG58U coax. I’ve wondered if the Ladder Line approach would improve performance for some time.

31. 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 kb9vwd@aol.com 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

32. 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.

33. 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.
IU1CYF
Paolo.

• 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 eham.net – http://www.eham.net/reviews/detail/4517.

73, —kv5r

34. 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.

35. 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

36. 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

37. 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

38. 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

39. 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

40. 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

41. 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

42. 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

• Yes, 80 feet is one of the “good” lengths to use. See page 3 of this article.

43. 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.

44. 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

Phill

• 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!

73,
–kv5r

45. 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 QRZ.com page.
ko6kL

• 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.

73,
–kv5r

• 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.
73,
–kv5r

46. 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.
73,
–kv5r

47. 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.
73,
–kv5r

48. 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.

• Keep the ladder line several inches away from fence and ground.

• 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.
73,
–kv5r

49. 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
Hylton

• 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