Re: Four Conductor Transmission Line

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.


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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