Re: What your mother didn't tell you about transmission lines
Posted by
Bill W4ZV on
Sep 11, 2011; 12:20pm
URL: http://elecraft.85.s1.nabble.com/What-your-mother-didn-t-tell-you-about-transmission-lines-tp6780383p6780644.html
Fred Townsend wrote
Rubber (parallel) lamp cord can be used as transmission line and it is
cheap. Z0 runs 95 to 120 Ohms depending on insulation thickness.
True, but it has very high loss (especially at higher frequencies) and should only be considered as a last resort. About 10 years ago ET3PMW was attempting to get on the low bands and only had zip cord available for transmission line. I thought it should work fine for 80 and 160. However, on 80m running 100 watts he was barely detectible here using a 1200' Beverage for receive. Once Paul got some good ladder line, his signal was typically S8 on 80m and S6 on Topband, where he made several hundred QSOs with North America even in summer QRN (June/July).
There is a loss graph on page 2 below but I believe ET3PMW's losses were much higher. Of course this could have been due to poor quality wire available in Ethiopia.
http://www.we0h.us/Amateur_Radio_stuff/Antenna/ZIP-Cord-Antenna/Zipcord-Antenna-7903031.pdf73, Bill