Re: Four Conductor Transmission Line

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.

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.


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.


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