Four Conductor Transmission Line


J Ed
 

The ARRL antenna book I have describes a type of open wire ladder line using four wires arranged in a square. The wires are basically two pairs of parallel conductors at right angles. Benefits should include less copper losses and increased balance with regard to nearby conductive objects. The only reason I can see for not doing this is the increased materials needed.

Has anyone ever used four conductor ladder line in their station? If open wire line is low loss, four wires should be even better. For QRP, this should be helpful.

Ed AE7TE


Dale Parfitt <parinc1@...>
 

Hi Ed,


Copper losses are already at minimum with ladder line. I cannot imagine you would be seeing any difference with 4 wire. If still concerned, just increase the gauge of 2 wire line.


As for balance, unless the antenna you are feeding is perfectly balanced (this rules out loops/ dipoles etc where trees and sloping terrain are involved, or metallic objects within ½ wavelength). The feedline will already be unbalanced. See W7EL’s article:


https://www.eznec.com/Amateur/Articles/Baluns.pdf


While it deals with baluns, it shows how easily a balanced antenna becomes unbalanced. Going to 4 wires does nothing to alleviate this issue.





73,





par logo 3





Dale W4OP


PAR Electronics, Inc


<http://www.parelectronics.com/> www.parelectronics.com


Voice: (828)743-1338


Toll Free FAX: (866)304-8479





Dale W4OP











From: qrp-tech@yahoogroups.com [mailto:qrp-tech@yahoogroups.com]
Sent: Saturday, April 30, 2016 12:54 AM
To: qrp-tech@yahoogroups.com
Subject: [qrp-tech] Four Conductor Transmission Line








The ARRL antenna book I have describes a type of open wire ladder line using four wires arranged in a square. The wires are basically two pairs of parallel conductors at right angles. Benefits should include less copper losses and increased balance with regard to nearby conductive objects. The only reason I can see for not doing this is the increased materials needed.


Has anyone ever used four conductor ladder line in their station? If open wire line is low loss, four wires should be even better. For QRP, this should be helpful.


Ed AE7TE










[Non-text portions of this message have been removed]


Joe Street <racingtheclouds@...>
 

Ladder line already gives incredibly low loss.  Probably the reason nobody bothers with 4 wire is the law of diminishing returns. Plus with 4 wire you need twice the materials, it costs twice as much, you get more than twice the weight, wind load, ice load etc.  Ladder line can sag in one dimension at least, but with 4 wire if it sags you get an impedance change due to wire sag on the inside of the bend.  More trouble than it is worth.

On Sat, Apr 30, 2016 at 12:54 AM, J Ed jedwardsat1@... [qrp-tech] <qrp-tech@...> wrote:
 

The ARRL antenna book I have describes a type of open wire ladder line using four wires arranged in a square. The wires are basically two pairs of parallel conductors at right angles. Benefits should include less copper losses and increased balance with regard to nearby conductive objects. The only reason I can see for not doing this is the increased materials needed.

Has anyone ever used four conductor ladder line in their station? If open wire line is low loss, four wires should be even better. For QRP, this should be helpful.

Ed AE7TE



Graham / KE9H
 

The only place I have seen four wire balanced line used was in high power broadcast stations, or marine shore stations with unusually long feedline runs.

--- Graham / KE9H

==

On Fri, Apr 29, 2016 at 11:54 PM, J Ed jedwardsat1@... [qrp-tech] <qrp-tech@...> wrote:
 

The ARRL antenna book I have describes a type of open wire ladder line using four wires arranged in a square. The wires are basically two pairs of parallel conductors at right angles. Benefits should include less copper losses and increased balance with regard to nearby conductive objects. The only reason I can see for not doing this is the increased materials needed.

Has anyone ever used four conductor ladder line in their station? If open wire line is low loss, four wires should be even better. For QRP, this should be helpful.

Ed AE7TE



J Ed
 

Thanks, all, for the input. I'm going to conclude that, since there are exactly no articles I can find on this type of line, nobody does use it and there's likely a good reason for that.

I may end up constructing ten to twenty feet of this stuff and running some tests versus a two wire line of the same characteristics, including a metal fixture near the line. The only attraction I can see is that it seems easier, for a given wire separation, the impedance seems to be lower.

My goal is to build a 200 ohm transmission line that I'll be capable of matching to a 50 ohm system with 4:1 transformers. The conductor separation is a little tough for this with round conductors. It's possible I can flatten the wire or something. I need to do more research before I start building anything.

This all started with a speaker wire dipole I made. I know speaker wire is not low loss, transmission line, but it can be made into such with some planning.

Ed AE7TE

On Apr 30, 2016 5:48 PM, "'Graham / KE9H' ke9h.graham@... [qrp-tech]" <qrp-tech@...> wrote:
 

The only place I have seen four wire balanced line used was in high power broadcast stations, or marine shore stations with unusually long feedline runs.

--- Graham / KE9H

==

On Fri, Apr 29, 2016 at 11:54 PM, J Ed jedwardsat1@... [qrp-tech] <qrp-tech@...> wrote:
 

The ARRL antenna book I have describes a type of open wire ladder line using four wires arranged in a square. The wires are basically two pairs of parallel conductors at right angles. Benefits should include less copper losses and increased balance with regard to nearby conductive objects. The only reason I can see for not doing this is the increased materials needed.

Has anyone ever used four conductor ladder line in their station? If open wire line is low loss, four wires should be even better. For QRP, this should be helpful.

Ed AE7TE



Dale Parfitt <parinc1@...>
 

The RF Connection has #18 stranded copperclad with polyethylene insulation. Spaced at 0.25” C-C and taking into account the  poly dielectric will land you right at 200 Ohms for a  2 wire ladderline.

 

Dale W4OP

 

From: qrp-tech@... [mailto:qrp-tech@...]
Sent: Saturday, April 30, 2016 9:56 PM
To: qrp-tech@...
Subject: Re: [qrp-tech] Four Conductor Transmission Line

 

 

Thanks, all, for the input. I'm going to conclude that, since there are exactly no articles I can find on this type of line, nobody does use it and there's likely a good reason for that.

I may end up constructing ten to twenty feet of this stuff and running some tests versus a two wire line of the same characteristics, including a metal fixture near the line. The only attraction I can see is that it seems easier, for a given wire separation, the impedance seems to be lower.

My goal is to build a 200 ohm transmission line that I'll be capable of matching to a 50 ohm system with 4:1 transformers. The conductor separation is a little tough for this with round conductors. It's possible I can flatten the wire or something. I need to do more research before I start building anything.

This all started with a speaker wire dipole I made. I know speaker wire is not low loss, transmission line, but it can be made into such with some planning.

Ed AE7TE

On Apr 30, 2016 5:48 PM, "'Graham / KE9H' ke9h.graham@... [qrp-tech]" <qrp-tech@...> wrote:

 

The only place I have seen four wire balanced line used was in high power broadcast stations, or marine shore stations with unusually long feedline runs.

 

--- Graham / KE9H

 

==

 

On Fri, Apr 29, 2016 at 11:54 PM, J Ed jedwardsat1@... [qrp-tech] <qrp-tech@...> wrote:

 

The ARRL antenna book I have describes a type of open wire ladder line using four wires arranged in a square. The wires are basically two pairs of parallel conductors at right angles. Benefits should include less copper losses and increased balance with regard to nearby conductive objects. The only reason I can see for not doing this is the increased materials needed.

Has anyone ever used four conductor ladder line in their station? If open wire line is low loss, four wires should be even better. For QRP, this should be helpful.

Ed AE7TE

 


Pete Ferrand
 

Eleven years ago I built a four wire transmission to feed a vee beam with 250' elements, used on 160-6m. It worked successfully for ten years, until I moved and took it down. I used 1/2" PVC plumbing crosses as spacers, cut in half "lengthwise" with holes drilled to hold the wire. The wire was #13 aluminum electric fence wire, same I used for the vee. Matching was with a balanced tuner in the shack.

I never measured the impedance, or the loss, or made a comparison with any other feedline in this application. It was the only time I used a four wire feed. Seemed to work about as well as two wire line I've used elsewhere. It was forty feet long and due to the four wires was much more stable than a two wire feedline and didn't need to be tied off or otherwise supported.

HTH,
-Pete
WB2QLL
Mount Pleasant, WI




-----Original Message-----
From: "J Ed jedwardsat1@... [qrp-tech]"
Sent: Apr 30, 2016 8:56 PM
To: qrp-tech@...
Subject: Re: [qrp-tech] Four Conductor Transmission Line



Thanks, all, for the input. I'm going to conclude that, since there are exactly no articles I can find on this type of line, nobody does use it and there's likely a good reason for that.

I may end up constructing ten to twenty feet of this stuff and running some tests versus a two wire line of the same characteristics, including a metal fixture near the line. The only attraction I can see is that it seems easier, for a given wire separation, the impedance seems to be lower.

My goal is to build a 200 ohm transmission line that I'll be capable of matching to a 50 ohm system with 4:1 transformers. The conductor separation is a little tough for this with round conductors. It's possible I can flatten the wire or something. I need to do more research before I start building anything.

This all started with a speaker wire dipole I made. I know speaker wire is not low loss, transmission line, but it can be made into such with some planning.

Ed AE7TE

On Apr 30, 2016 5:48 PM, "'Graham / KE9H' ke9h.graham@... [qrp-tech]" <qrp-tech@...> wrote:
 

The only place I have seen four wire balanced line used was in high power broadcast stations, or marine shore stations with unusually long feedline runs.

--- Graham / KE9H

==

On Fri, Apr 29, 2016 at 11:54 PM, J Ed jedwardsat1@... [qrp-tech] <qrp-tech@...> wrote:
 

The ARRL antenna book I have describes a type of open wire ladder line using four wires arranged in a square. The wires are basically two pairs of parallel conductors at right angles. Benefits should include less copper losses and increased balance with regard to nearby conductive objects. The only reason I can see for not doing this is the increased materials needed.

Has anyone ever used four conductor ladder line in their station? If open wire line is low loss, four wires should be even better. For QRP, this should be helpful.

Ed AE7TE





Kirk, NT0Z
 

Ed and the gang,

This stuff IS interesting...and is mostly used at VHF as an alternative to expensive coax or hard line. At HF, losses on a good two-conductor open-wire line are low enough to not warrant bothering with 4-conductor line -- which is more difficult to physically install and terminate.

A caption to a column I wrote a while back has the source info:

"Need a low-loss, 300-foot-long feed line for your 2-meter Yagi that won't require robbing your college fund (or a cable TV truck)? The four-wire open-wire line shown here (author's full size mock-up made from slices of 2 X 2 lumber and string trimmer line) has loss characteristics that rival 7/8-inch hard line (about $5 a foot and $30 each for connectors), but at a fraction of the price. With two-inch spacing between the wires, this easy to build feed line has a 200-ohm impedance, which makes for an easy match to 4:1 baluns, and only 0.6-dB loss per 100 feet at 144 MHz. Henry Elwell Jr. N4UH, provides details in the January 1987 and October 1980 issues of Ham Radio magazine. (NT0Z photo)"

Regards,

--Kirk, NT0Z


AD7ZU <ad7zu@...>
 

Ed,

A long time back .. 1980 or so?  I  built a 4 wire transmission line to drive a folded dipole at a height of less than a 1/2 wave. at that height the impedance is well under 280 ohms. .. and a good fit for a 4 wire line.  A 4 wire line might also closely match some of the skywire loop designs. 

There are several advantages:

 the impedance is lower.   maybe about 35% of a similar sized 2 wire open line (as i remember) would be a good estimate. but check the formula.  it should be in the ARRL antenna book?

There is less sensitivity to the orientation of the transmission line to ground.

 The losses are lower, but with an open wire line the difference is probably negligible.

 The power handling is higher but that isn't an issue for us QRPers


Randy
AD7ZU



From: "J Ed jedwardsat1@... [qrp-tech]"
To: qrp-tech@...
Sent: Friday, April 29, 2016 9:54 PM
Subject: [qrp-tech] Four Conductor Transmission Line

 
The ARRL antenna book I have describes a type of open wire ladder line using four wires arranged in a square. The wires are basically two pairs of parallel conductors at right angles. Benefits should include less copper losses and increased balance with regard to nearby conductive objects. The only reason I can see for not doing this is the increased materials needed.
Has anyone ever used four conductor ladder line in their station? If open wire line is low loss, four wires should be even better. For QRP, this should be helpful.
Ed AE7TE