I'm sending this again because I didn't see it come through:
You are mistaken. 25' of ladderline is only about a tenth of a wavelength and does not invert impedance. I suggest you download Dan's TLDetails program: http://ac6la.com/tldetails1.html and play with it. Put in what you think, or have measured, the feedpoint Z is then select one of the Wireman ladderlines and see what happens as you change the length.
You may find some data on zip cord as feeders, but I would avoid them like the plague, particularly as you are trying to solve a problem that doesn't exist.
Wes N7WS On 11/7/2017 9:12 AM, Michael Blake wrote:
Thanks to all of you for your responses. My need for a lower impedance parallel line is not so much a matter of loss but to minimize the impedance transformer effect a 25’ window line (400 ohm) has when terminated in a low impedance load. My real concern was for the ability of the line to survive in weather and sunlight and its RF voltage breakdown rating. The two data references were quite helpful. Thanks again! Michael Blake [email protected] From: Michael Blake Sent: Tuesday, November 7, 2017 9:12 AM To: Elecraft Mailing List Subject: [Elecraft] Off topic feedline question My 80M antenna is a low, loaded dipole fed with balanced window line. As the center impedance is low the high impedance window line tries to invert the impedance to a much higher value. The feedline is only 25' long and terminates in a 1:1 balun which is then connected to a remote autotuner via 24 inches of 9913F. The question is: Has anyone run any RF loss tests on the commonly available 12 gauge clear PVC insulated "speaker" wire. The impedance would be quite low, probably in the 90 ohm range, and world certainly handle the applied power (500 watts) but I have not been able find any information regarding RF loss. Michael Blake [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
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