Ladder Line, Twin Lead, Window Line (
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- čas přidán 25. 06. 2024
- Let's explore the opposite of coax, which is transmission line made of two parallel conductors. I use the ARRL Antenna Book and a little of Wikipedia as sources. This is in response to a question from David Spivey, KR4WX.
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Enjoyed how you casually pointed out the error in the antenna textbook. Mark of a true pro.
I concur
I was running a G5RV antenna, which had 30 ft of window-line connecting to coax through a balun. The performance was ok, but not great. I decided to take the balun and coax out of the equation, and ran the window-line straight into my station, connected directly to my old Palstar antenna tuner (which has connections in back for window line leads). The performance is dramatically improved! I am now sold on the benefits of using window-line.
This is not a surprising result. The "ATU" will have a built in balun. So you have effectively just moved where the balun is located. However, you have removed the coax from the configuration on the antenna feed side of the ATU. The coax will have been causing loss compared to the ladder line. So, you get better results on rx and you should be getting more power to the antenna.
"...(or him...these days)..."
Heh heh...you rock Dave! Thanks for another great video!
73
Tony KB9A
Great video Dave, and as always, your strive to inclusiveness is a breath of fresh air.
For most of us born in the mid 80s to now, a lot of this common knowledge is uncommon! This video explains a lot
Finally understand electrical difference of various antenna line and their uses, thanks.
Thanks David. Getting back into amateur radio and purchased a 102 foot G5RV from DX Engineering with “window line”.. I was going to attach the center off the tower but now will use a tree limb at about 50 feet instead. There is a 450 ohm to 50 ohm connection point. According to your video, that would be a 9 to 1 balun. Interesting. Will keep all away from the gutter and tower. A most instructive video. Thanks. 73
"...or Him these days" LOL. Dave. Love ya bro!
OK. thought it was just me! LOL ;)
Sadly
Fantastic information on ham radio or sw radio antennas !! Amazing stuff!! Thanks DAVID!!👍👍👍👍👍
Brilliant. I have been wondering about precisely these things. Thank you!
This was very helpful; new technician class license here, but have been a SWL for over 60 yrs using antique hallicrafters radios. Currently a S38B with a MFJ-1777 doublet. Great, informative video, thank you so much.
KO4BGD
Thanks Dave. So glad I subscribed to your channel.
Wow, that was SUPER informative and explained so many things. Thanks, Dave!
That was a great explanation, Dave. great video. I learned a lot!
Ladder line is great...issues revolve around how to get it into the shack! That would be a great follow-on discussion. 73 - Dino KLØS
Excellent explanation. Thank you
Thanks for the lesson Professor OG
Dave, I use the smallest diameter of PEX tubing (inexpensive) to make my ladder line and it works well!
Dave, thanks for your very clear explanation of balanced feed lines. I learned a lot and will be using that knowledge on my next antenna build. 73 de Chris W6NOB
i'm a CBer on a farm and everything outside the house just got switched over to ladderline. vertical folded dipole fed by 450 up in a 80' pine. before i had a IMAX and 150' of 8x so the boost in signal levels was DRASTIC when i basicallly put the ears right to the tree with this new feed. wasn't really into dumping a ton of money on coax to get up there. so now im working on some 1.25~ doublets so i can do a 4x array for the west coast
Excellent David. Greetings from Chile. Saludos CE3-THK
Ive been searching all morning for the very info you provided. Thank you. Trying to confirm the ohms of a homemade ladder line to determine if an old homemade trans match has the ability to handle it is a challenge. Hope you are well. 73
I was a young buck just starting college when they were building Raymond James Stadium - I lived in St Petersburg! Small world! Friend of mine took me to a game, I think the year it opened - Tony Dungee was the coach I think. Idk, I'm not that big of a sports guy.
Really REALLY mind blowing how the energy is carried in the dielectric. It's definitely above my pay grade :D I'm a software developer, but I did take some EE courses which I really liked, but I landed in computer science partly because back then, people were getting twice the bucks straight out of college than electrical engineers ... and then that bubble burst! But I loved comp sci too, so it wasn't like I did it just for that...
My background previously as far as electrical, was mostly DC, some AC but basically getting power from "here to there". RF stuff really can be mind boggling!
Just got my general @ 73 and you are answering questions I didn’t know to ask... thanks Dave for giving back...KI5MOM Mickey
Fifty ohm-ish cable... Cable with a beard?? :)
Thanks Dave. I learn something new every tim I watch one of your videos. - VE7MHJ
Thank you!
A few weird things about "window" line. First, everyone seems to be selling line with copper clad steel conductors. There is a low frequency "cut-off" for losses. At lower frequencies, skin effect has lower impact forcing the current deeper into the conductor's steel core. I don't remember where I found the graph, but commercial window line is better above 4 MHz than below. Probably not significant for most users, but a legal-limit station on 160m might notice it. Second, because the conductors in "window" line are mostly steel, they tend to be extremely stiff, not to mention difficult to cut. I had some line that had #14 stranded conductors. I needed my fencing pliers to cut the stuff, but it was far more flexible. Third, you mention rain/ice effects. This is primarily due to the accumulation of rain/ice on the areas of solid insulation between conductors. I can't figure out why the "window" line manufacturers do not make the windows much larger. They could easily save and recycle a large percentage of the polymer if they would make much larger "windows" and very narrow (say 1//4-inch wide) spacers every few inches. This would make "window" line more closely approximate true ladder/open- wire line. Along with saving insulation, this would make the line much less susceptible to the effects of rain/ice. Finally, a small challenge: Previously you did a program explaining why 50-ohm was the standard for nearly all amateur and commercial radio feed lines. It would be interesting to repeat that program for parallel conductor line. Finding the most efficient impedence might be an interesting study. 73 DE KG5AR
He mentioned that. The spacing usually is upto 6"; but it can be as wide as 12".
It depends on the power and the frequency of operation.
More power needs wider spacing.
The lines (should always) carry currents of equal magnitude but of opposite polarity. The ladder line does not radiate (or receive) because the fields (electric and magnetic) get nullified to a large extent. As he explained the intensity of the fields around the conductors die out as per the inverse square law of the distance from the lines.
For 30 MHz and above (50 MHz) the spacing can be like 6". Otherwise the lines may radiate. So the frequency of operation dictates the separation apart from the power that has to be handled.
You can choose to have the diameter of the conductors (including copper tubing) spacing and hence the characteristics impedance of the line for your need.
The 50 ohm standard was very well explained by him already, I suppose.
Regarding the dimensions of the windows or the polyethylene as you think it can be optimised; at the same time I believe it has been optimised for strength and integrity. Yes the water sticks (though it's a hydrophobic substance) at least for a while even after the rain (or fog, dew etc) and certainly increases the capacitance of the total system causing the SWR to raise considerably to the extent that it may be difficult altogether to transmit. But if too little polymer is used there is every chance that the lines might get twisted in the winds causing total havoc.
Yes the conductor maybe made of copper claded steel and the question of conductivity is a real problem. And this happens with the single strand; the multistrand #14 wire is flexible and very good which I have been using happily.
Thank you.
Ladder line is the best transmission line for a wire dipole.
I used plastic tent pegs for spacers.
On my CZcams channel
Great video !
Thanks!
Figure 23.21 in the AARL Antenna Book (24th edition) is most informative.
Very great Information og
Hi Dave,
Very good info. Ladder line spreaders can be found at DX Engineering by SOTAbeams their SPC-100 and on Ebay as ladder line spreaders, but a bit pricey. Stay safe. 73 WJ3U
Thanks for another great show. You covered the subject much better than the book does. KD9HWH
Just to be argumentative I have used wide spaced line with wooden spreaders (wanted to do it in an old school way) I used 1/2" dowel boiled in oil, it did work well but a few years exposure to the weather did still destroy them.
18:04 When running a doublet and an antenna tuner, do you still suggest a 9:1 balun? Paul from Palstar suggests a 1:1
My vision of your explained ladder line, energized..
The iron chips around a cylinder magnet, forming in the field or flux, on each conductor and the oval over the two ..? Eddie currents..
It is worth saying, that current is the flow of positive charge. The pointing vector shows the direction of energy flow.
Many many years ago 60-70 years most all TV antennas used ladder lead I have even seen ladder lead strung from power pole to power pole as a primitive cable TV service way back in the 60's
Excellent as always Mr. Casler - thanks for that. Very timely for me: having poured concrete for the tower base a couple of weeks ago, looks like the Doublet should go in next weekend all being well, and I intend to feed it with 450 ohm window line. My conundrum is whether to feed the window line all the way into the shack (garage) to a balanced ATU I have obtained, or use a 9:1 balun and convert to co-ax before bringing it indoors (perhaps more convenient?)... I have the components for both approaches so will probably experiment between the two..! 73 de G1AJH
How did you do this Andy? I have a doublet going to an antenna tuner and used a 1:1 balun.
Good explanation 👏 thanks.
Greetings,
Matthias 👋
DL1NDG
Thank you. Questions answered. More questions raised.
These may have been answered already.
If electrons travel on the outer skin as frequency goes up, how does corrosion affect the line ?
Other than practical limit, is there a limit to how much impedance is too much ? 1:200 balun for 10,000 ohm ladder line ?
The electrons travel toward the surface of the metallic part of the line. For example, on an aluminum antenna, there is a layer of aluminum oxide that actually serves to protect the aluminum. The current travels just below this layer. A 1:200 transformer would be pretty hard to construct.
I am going to put up an antenna like his. The center feed point will be held up by my 60 foot Ron tower. I am thinking about putting PVC pipes about every 5 feet to hold the window line away from the tower and a stand off near the top where the antenna will connect. Would about 18 inches be far enough, or what do you think is the best to hold the window line away from the tower?
What's the difference between a "doublet" and a dipole?
A doublet is intended for use with a tuner and may not be resonant on any band. It is fed by parallel conductor line. A dipole is generally center-fed with coax, and is made to resonate on the intended band of operation.
Dave. question im putting up a zero five -80 vertical not resonate on any band. I need a run of coax of 75' from radio to antenna. im using LMR 400 but at that im only 89-90 % efficient with a 100 watt station so im loosing 10 watts in the coax , im thinking a remote antenna tuner , what about 450 ohm wind line with PL259 on each end ? can that be laid on the ground? or buried ? just trying to find something to cut my losses any feedback will help
Water's relative permittivity is 80. When it rains the capacitance of the window line system goes up and the SWR shoots up making you stop transmitting.
I had a g 5rv in the air it got hit with lighting. it blew the top of the g 5rv . I wonder if the ladder line is good to use. I also got a peice that I can put coax on and add the wire of g five rv and use the wiring of the g five rv wire attached to the spliper with coax If I guess right it would not be consider a g five rv ?
Where did you take your magnifying lamp?
Hi Dave....I use 450 window line....all I ever read was to use a 1-1 current balun....which is what I use.....what probs with this set-up cause me.
don't quiet under stand this. I had ladder line on my 706 and it worked good. I want to put it back up. there is some kind of thing on the end of the line that coverts the end of the ladder line to coax. I'm wondering about the lighting strike that hit this thing. would the ladder line and i guess what is a blum at the end of the ladder line that is in the house. I don't know if this is confusing or not.
you're a great teacher! maybe you could tackle LC networks next and use your abilities to simplify this complex topic!
One of my Amateur Extra class training videos deals with this very topic.
@@davecasler I can't find it
You know your onions!
Two quick things. My ZS6BKW feed, 450 ladder line is close to the coax from a EFHW 8010 antenna. The end fed is straight out of the rig, the other one is switched out of line at the rig but when I transmit it shows power on the tuner meter attached tor the ZS6BKW. I separated them a bit more but tomorrow I am moving the feeds further apart to spread them more. Second is what about whether the twin lead has to be really flat and straight or can it be a little bent and twisted? Must it be straight?
Yes, you'll see some bleed-over from one antenna to another. Be cognizant of this if you have another antenna connected to another receiver. Re the flat line, you can twist it like a ribbon and if it's bent a little it won't affect your signal in any meaningful way.
Dave, Doesn't the frequency being used determine the (ohm) impedance of the line?
I agree Jerry. You are absolutely correct. To match the impedance, a 450 or 600 ohm ladder line or window line to 50 ohm coax, it is not as simple as using a 9 or 12 to 1 balun except if the dipole is its resonant frequency. Most urban hams use long dipoles fed with ladder line as an all-band antenna. As you state the impedance between the ladder line will vary in relationship to frequency. In short at the termination ends it won't be 450 or 600 ohms. For all-band usage a high quality 1:1 current balun would work best (2 - 50 MHz).
What do the "windows" do and why does my wire skip every third window? Thanks for the great videos.
Less surface area for water, snow, ice, or dirt to accumulate. Less wind loading. Less weight. But part of the dielectric is now air, so that changes the electrical properties of the feedline slightly.
I guess heavy fog would also change the SWR.
Love the Videos Dave Thank You.73 DV7NIB
So, why not make ladder line that is 50 ohms? Would there be a benefit over coax?
The wires would be too close together to make it practical.
My wife would give me her hair curlers along with divorce papers lol
Her or " him " these days 😊, love that comment Dave, 21st century " life !" ..glad it's the same in US as UK !!! PC correctness!!!
What happened at 7:50 ? XD
didn't they call it window line back in the B&W tv days because people ran it thru windows? the flatness allowed the window to be closed
No
So here in the Northwest we should not use window or ladder line ... lots of rain!
Lots of people use it here in Oregon. 600Ohm spaced and hundreds of feet long in the Pacific NW.
@@forgetyourlife all it does with my folded dipole on 11m is drop the resonant freq when it gets wet
Theres always a "however" ....lol
Super low loss. Just more fussy to run.
Anyone that says magic doesn't exist has never studied RF ;) lol
magic is just another word for unknown.
Great video, really learned something new 👍 K7OSS
All those formulas make it clear to me...that I will never make it to the General license level, much less extra. 😧
Nothing to worry about. None of these are on the general or amateur extra test.
If I can make Extra so can you. Memorize the question and answers, try to understand it best you can and go take the tests. I can't do math beyond simple arithmatic and passed the Extra with a 44/50 on the first try. HamStudy app is a great resource and fun to use. Goodluck
First Comment, WV8DCR
birds are a pain in the arse.
Way over complicated. Unless your doing scientific experiments the average ham can disregard 90% of this video. Your going to hook this balanced line to your external tuner and it doesn't care if it's 200 ohms or 600 ohms. Just keep it away from metal the best you can it doesn't need to be perfect and it will work great. It's much easier to work with then you would think. There is lots of information on the net about how easy and efficient it is.
This is one of the nice presentations he ever made. You would want to watch it again 😉
Not sure I agree entirely that such large variations in impedance doesn't matter. In general terms, the higher the impedance the more efficient. So, maybe not a big difference say 550 to 650 but going from say 300 to 600 should make a big difference. That's why, especially on tx, 600 Ohm ladder line is popular versus 300 Ohm window line.
@@Steve-GM0HUU you please refer to my reply to Bill Brown in the comments section.