450 ohm ladder line discussion: Hints & Kinks

[N6YW]

Greetings to all.
A little while back, I finally installed my much awaited Cobra Ultra-Lite antenna, fed with ladder line. The results have been superior for my local work compared to the vertical.
I am using the Johnson KW matchbox. It does a fine job. However, I have noticed some things about using ladder line and perhaps we could all share some insights to using this sort of line.
I have found that being in contact with tree limbs and an abandoned telephone line caused my SWR to fluctuate and more so using QRO. I noticed that when the breeze picked up, this would become more noticeable. So, I rerouted the line so that it gently hangs under and over these obstacles without touching and not being bent at right angles. Apparently, this worked.
Today I tuned up for the 3870 AMI net for this evening and got a match but I noticed it was doing it's little dance. So, I went outside and did the fore mentioned task and re-tuned. It is now stable and staying put.
I learned that keeping ladder line away from limbs and other objects make a difference in how well the tuner can keep the transmitter happy. Over a period of 30 minutes now, even with a gentle breeze it is staying put.
I have heard of but not experienced yet, that ladder line in wet weather may cause some problems.
Would anyone like to elaborate on this and other subjects concerning ladder line?
Thanks,
          73 de Billy N6YW

[W1ITT]

Balanced line has to be treated with a bit of respect for the physics involved.  If you put things like tree branches or building eaves or tower legs in it's close field, usually described as equal to the line spacing, it will upset the impedance.  If you use the so-called 450-ohm line, aka "crappy brown stuff" you also have to consider the effect of rain, snow and ice on the plastic webbing, also upsetting the impedance and maybe creating a leakage path.  Real open wire line suffers similarly from rain and snow etc on the spacers, but the effects are much smaller in proportion to the "brown stuff".
Coaxial cable is preferred by many because it can be snaked through walls, ship bilges, and along or under the ground with no ill effects.  That being said, all the big short wave curtains and most of the larger HF log periodics that I play with use  balanced line.
As a matter of perspective, things are not really critical on the 80 meter band.  As long as your transmitter will load, and you have done the best that you can reasonably do to keep your balanced line away from objects,  don't obsess over SWR.  I have over 600 feet of real open wire line around here, between my 80m phased arrays and the lines that feed them.  It looks cool, works well, and it takes a serious ice storm to push the SWR up to where it bothers.  In the future, if the situation allows, replace that "brown stuff" with real home-made open wire line.  It bespeaks radio savoir faire, and my even add a half a decibel to your signal on 80 meters.

[N6YW]

Norman
Thanks for your sage wisdom. I have a love hate relationship with the giant Chinese Elm that occupies our back yard and has been the source of endless frustration over years regarding antenna erecting. Having finally solved the problem in getting the antenna above the tree into the clear, I had a heck of time guiding the brown stuff down through the middle canopy of growth. Fortunately, I was able (today) to guide the line in a manner where it doesn't touch anything at all. Like your understanding wife, mine is smarter than I am much of the time and suggested I do what I ended up doing (yeah, I openly admitted that) in order to prevent me from removing the offending branch. There is a thread here on the forum that deals with the subject of open wire feeders and the differences of width, what wire to use etc. I will peruse that for a refresher. It will be awhile before I change out the line though. I need to pull my catenary all the way across to the main mast in order for me to reliably lower and raise the antenna.
That will happen with phase two of the project this fall when the foliage begins to thin out.
Even though it's not the best stuff in the world, this ladder line serves the purpose here at this QTH where the obstacle course is tight. In a perfect world, I would have a traditional "Shack" out in the middle of the field with open wire feeders going up as high as possible to a double extended Zepp or what ever contraption that kicks a good signal, being fed by a transmitter worthy of such an installation.
For now, I will settle for the GK 500, ART-13 & the BC-610E... and the brown stuff.

[KB2WIG]

I've heard of people cutting out much of the webbing that makes up the CBS. Supposedly, it reduces the effects of the weather on the stuff.


klc

[Steve - K4HX]

I agree with Norm. When you get the chance, switch to open wire line. At a previous location, I had a 130 foot wire fed in the center with the ladder line. The system worked quite well, even yielding contacts on 160 meters. But the tuning would change with rain and snow. One evening a dreaded tree branch got involved and the tuning was really off. So was the ladder line and the branch. The branch was smoldering and the ladder line had melted, including one of the conductors. I switched to open wire line shortly thereafter. The tuning anomalies ceased.

[K3ZS]

Also agree,  I am using the brown stuff.   On 80M not much of a change when wet, 40M requires a little retuning, 20M and above almost unusable when wet.   I have a 150 ft feedline.

[N6YW]

Okay.
This is giving cause for a plan. I viewed some videos on Youtube by some very interesting people. N4LQ came up with a very cool idea using a box of cheap ballpoint pens for insulators.
See it here: https://www.youtube.com/watch?v=qzFKGB6qkXs

I also enjoyed this guy, a true homebrew and cost conscious ham, ZL1BJQ. Not sure about hot melt glue though: https://www.youtube.com/watch?v=D--K4Uc5p0I

These guys and others all use insulated wire, likely 14-12 awg. What do you recommend? It seems that the traditional way would be non insulated wire using wire wrap methods to secure to the spreaders. Tedious but old school and built to last. Is there a good argument for not using insulated wire? THHW has a 600 volt rating jacket and is water and fuel proof. Having said that, it seems that solid core wouldn't want to curl and cause the line to twist as much. It would likely stay more rigid between the spreaders. Any thoughts on this?
I have several hundred feet of black 14awg THHN solid. I also have a bunch of stranded THHN.

And finally, the easy snap on spreaders made by 73CNC. Seems like a cool product but not cheap if you make a long run. UV resistant grey PVC conduit would make good spreaders too.
And finally, unwinding a couple of surplus transformers to use the formvar coated wire. Seems that would be good material. Random thoughts.

Billy N6YW

[WD8BIL]

That being said, all the big short wave curtains and most of the larger HF log periodics that I play with use  balanced line.

6 1/8" to 8 3/16" diameter transmission line is much more expensive for the really high power stations to use on curtains. It, in most cases, requires either vacuum or nitrogen pressure to handle increased dielectric.  Yet another expense.

Big Station Toys

[N6YW]

Another set of videos by a clever ham.
1.  https://www.youtube.com/watch?v=0Q6bO0kue80
2.  https://www.youtube.com/watch?v=o_VCFyM_06o
3.  https://www.youtube.com/watch?v=E0oVbCN_w_U

[N6YW]

Without having read any textbook passages at length (in depth) on these types of transmission lines, I am starting to understand more about why it has a quality that makes me want to never use coax for HF antennas ever again.
The dielectric loss is not a problem compared to coax. I am gathering that the additional spacing that many use in their home brew line makes the performance better than the brown stuff. Am I correct to assume that this increase in spacing, say upwards of 4-6" inches is better at fending off the moisture issues associated with the brown stuff? The more I read up on this subject, the more I want to yank that stuff down.

[WD8BIL]

The dielectric loss is not a problem compared to coax

And on HF to 6 meters it is not a problem with coax either.


 RG-8/U FOAM loss in dB   1.2@50MHz  1.8@100MHz     

[K1JJ]

An extreme example of what you are trying to achieve:  

The BEST open wire line I ever used was two parallel #10 wires spaced  12" apart.  NO spacers - the wires just pulled taunt from the top of the tower at 100' to a post on the ground with a 'T' top.  Same thing run to the house on little poles with T tops and insulator supports.    Rain had no effect.  Losses were as low as they can get. No time wasted making and mounting OWL spacers.   But we need the clear run and solid center support to do it, of course.

12" spacing seemed to cancel well on 20M, though I never used it on 10/15M. I suppose it would be OK there too... matter of degree.


But at this point (last 15 years) I use all 3/4" hardline buried underground in 4" PVC piping.  I really like the instant band switching and not having feedlines hanging in the air all around the house.  

When using "reasonable" feedline lengths, there is virtually NO difference in signal strength between an openwire fed dipole compared to a well matched coax fed dipole, contrary to what we sometimes hear said on the air. They both have their advantages and some of the loudest stations on the air use coax.  I can name a bunch is needed...     (Don't forget that the OWL ant tuner has some loss too)


T

[N6YW]

An extreme example of what you are trying to achieve:  

The BEST open wire line I ever used was two parallel #10 wires spaced  12" apart.  NO spacers - the wires just pulled taunt from the top of the tower at 100' to a post on the ground with a 'T' top.  Same thing run to the house on little poles with T tops and insulator supports.    Rain had no effect.  Losses were as low as they can get. No time wasted making and mounting OWL spacers.   But we need the clear run and solid center support to do it, of course.

12" spacing seemed to cancel well on 20M, though I never used it on 10/15M. I suppose it would be OK there too... matter of degree.

Well stated...
My little 30 X 90 Venice Canal lot has to be considered as a major factor in all of my station antenna choices. I have 100' ft. of 5/8" hardline waiting for use some day but I don't have the luxury of a tower. I do have this useless Chinese Elm tree in the back yard. While it's a great looking tree and provides a lot of shade and oxygen, it's the equivalent of the obnoxious cousin who is ALWAYS at a family function and never shuts up, has no manners and doesn't clean up afterwards. Just getting the little Cobra up in the air was a major pain in the ass. I did it all by myself too which didn't help but I don't like waiting while my stupid neighbors complain to the FCC because my signal was interfering with the cordless phone (true story).
Now that I have this 450 ladder stuff experience under my belt, I have come to the conclusion that it must be replaced. Number one, it cracks easily and doesn't hold up for a long time. It's a cheap way of getting a signal out but the frustration of using it makes it a constant hassle using the matchbox.
I am setting down on paper, a design from scratch, of the plan to route and support the line from the shack entrance so I don't have to worry about it fouling. This will be another adventure of many to come.
Also, the entrance into the shack to the matchbox. PVC tubing, capped on both ends with hole drilled in the caps for the wire. This will terminate at the massive DPDT knife switch.
BTW, last night, it held tuning better than before but it did eventually drift from 1.1 to 2.3.

But at this point (last 15 years) I use all 3/4" hardline buried underground in 4" PVC piping.  I really like the instant band switching and not having feedlines hanging in the air all around the house.  

There is virtually NO difference in signal strength between an openwire fed dipole compared to a well matched coax fed dipole, contrary to what we sometimes hear said on the air. They both have their advantages and some of the loudest stations on the air use coax.  I can name a bunch is needed...     (Don't forget that the OWL ant tuner has some loss too)


T

[Pete, WA2CWA]

N6YW and all: When you quote a previous post, take care where the bkt quote bkt and bkt /quote bkt are positioned (especially the bkt /quote bkt). If you don't, it's difficult to read who's writing what and what's being quoted.

Billy, I corrected your post.

[N6YW]

Pete
Thank you.

[W1ITT]

Tom and all...
You mentioned your 12" spaced open wire.  Most of the big shortwave curtains use something similar, but about 14" spaced, and with two wires (connected every few feet  by metal spacers) on each side.  They are required to meet spec at least up to 26 mhz and sometimes higher depending on customer wants.  Properly installed, they are just fine and I have measured very good balanced to unbalanced (common mode) ratios on the lines.
As an aside, I also worked with an open wire coax in the Middle East.  The center conductor was a cage of wires about 6" or so in diameter, surrounded by another cage of wires perhaps three feet in diameter.  Rings held the cages round, and they were hung and tensioned periodically to maintain concentricity.  It was rated for over a megawatt of medium wave power, and it worked out to around 110 ohms impedance.
Again, the key to making any transmission line work well is paying attention to physics, which mostly involves a good clean repeatable installation.
My own open wire is 12 gauge bare FlexWeave spaced about 4" apart every 33" by UV stabilized pigmented polyethylene  (UltraEthylux) that was left over from some FM radomes.  Despite dire warnings about the FlexWeave, my newest lines have been up for seven years and I've never had a failure.  If anyone wants to buy material, Mcmaster.com has HDPE polyethylene and Delrin, both of which do well in UV exposure if you choose the right stuff from among their offerings, and they are pretty good people to deal with, even for small non-industrial orders.
Who will be the first to put up a run of open wire coax out across the back forty?  (Not me !)
Norm W1ITT

[N6YW]

Norm
I am curious about the choices of width of separation. In my case, does it really matter if I go with 4" 6" or 12"? How does this change affect the performance of my particular installation? For me, I guess it really doesn't matter as my run to the feed point is approximately 80' ft. I am guessing here because I am a musician... I can only count to 4 and my math skills are non-existent compared to you guys.
Calculating all of the various elements of impedance stuff, current distribution etc... It's all mush in my mind. I understand the concepts but applying them with math is not going to happen. My brain will not allow that, trust me. In the end, good performance and management of such a contraption becomes the primary focus. Building it will be easy.
Thanks in advance!
Billy

[K1JJ]

Once you get past  14" spacing or so?  the feedline impedance starts changing very little when using thin wire diameters.  Check out a web OWL impedance calculator and try various spacing to see.   200 ohms to 700 ohms is the working range, more or less.

That said, for multiband OWL dipole use, it will make virtually no difference if the openline is spaced 2" or 14".  On some freqs, feedline lengths and dipole lengths it will be near a perfect match - but on others it will be way off. But with OWL and balanced tuner, the SWR is not a loss problem, so who cares...  (as long as the dipole is at least 3/8 long wavelength on the lowest freq.)

As long as the OWL cancels and does not radiate due to an imbalance or excessive spacing, you are fine.

The exception is you want a specific OWL impedance if you are optimizing a system for a single band or perfect match - like say, a three wire dipole, folded dipole or multi-element wire array for a single band and want minimum swr for balun matching or whatever reasons...


Otherwise, in general, 4"- 6" spacing is probably a good choice for rain, ice and twisting compromises.  When using no spacers like I did, 12" or larger is good to keep wire sway from changing the impedance in the wind.  

Spacing distance, within reason, is no big deal, really.   Do whatever works best for you physics-wise, as said recently here by a wise man....


Most important for least losses:
The thicker the wire, the better.  The less spacers used the better.   The best dielectric: air

T

[W1ITT]

Billy..
The 14" spaced line and similar are used on systems running 500 kw or more, so leakage across the big ceramic dogbones that set separation at intervals becomes important, especially if you don't have a crew of flunkies to go out and clean them every so often.   For the rest of us who run a kilowatt (or so..) 4" line separation is easy to work with.  Use good spacers and keep thing tight.  I take two wires, tied to a tree, string insulators on, tie the other end of the pair of wires to my tractor and gently tension the pair.  With the pair at waist height, I measure the spacing, slide  insulators to the indicated spot and wrap and solder tie wires to hold them fast.  My 33" spacing is a direct result of having a hardwood stick in my shop of just that length.    I end up with nicely spaced line that looks good in the air.
As Tom says, 4 to 6 inches is fine, and will depend partly on what you can get or make for spacers.  When you get up over 100 kw, we'll have another conversation.....  And yeah, you gotta have a manly DPDT knife switch in the shack to add to the mystique.
Norm W1ITT

[N6YW]

Tom & Norm
Thank you. That clears things up for me in a logical manner.
I won't be putting out the K1KW signal on 75 but maybe some of you may hear me this Winter.
I must admit, the Ladder Snap spreaders made by 73CNC look mighty tempting and is a very
slick solution without being overly time consuming. I at least have a knife switch that will suffice.

[N6YW]

A quick sketch of my plan for line entrance into the shack. I got the idea of static discharge using a spark plug from a W5 in Texas. Genius. When you here the popping, it's time to hit the switch. Setting the gap is easy. I love this.

[W1ITT]

I have that same model of DPDT knife switch.  It makes me feel like a "real radio guy" when I operate it.
Norm

[n1ps]

On the Pex line, I don't know if the product has a UV inhibitor (normally titanium dioxide) in it's chemistry.  A review of their specs or datasheet may indicate this.  A nice idea for a spacer though.  To gain some additional UV protection you could run a clear coat over the pipe.  I would use epoxy and not hot glue to set them in place.

On OWL versus coax I think they are about the same as far as performance.  The resonant coax lines must use a low loss line like hardline or RG213.  The 2 strongest stations I hear in this region, one uses OWL and the other coax. 

I must admit that I still use the ubiquitous CBS.  One of these days I will upgrade.  In the meantime I have to be careful when WX is present. 

Norm...I'll keep the 14" OWL in mind for my next 500KW TX.  How many FETs would that take?   

p

[ka4koe]

It appears PEX does degrade from UV...

http://en.wikipedia.org/wiki/Cross-linked_polyethylene

[N6YW]

I'm not too worried about the UV longevity of the spreaders. Most of them are obscured by the canopy of the tree. It's all good.