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Author Topic: Ladder transmission line  (Read 3086 times)
W9BVG
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Posts: 10




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« on: September 23, 2017, 09:53:07 PM »

Does anyone know if Davis line is the only brand that's not completely perforated, i.e. there are ~3 in.-long sections of un-punched dielectric (polyethylene) between groups of 3 equally-spaced "windows" (appears the punching wheel has some missing teeth!).
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KD8IIC
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Posts: 700




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« Reply #1 on: September 23, 2017, 10:37:04 PM »

   Charles; In reply to your question; I have yet to see any of the 450 ohm window line produced in any other way.
   All manufacturers have the offset spacing dielectric width.
   I have had old head ops tell me a good trick is to cut out the spacers as much as possible, leaving the small   portions in tact and only thoise absolutely needed to support the spacing integrity. This is to decrease the capacitance if the line, so they said. I have not tried it but it is assumed to improve the performance of the window line in wet conditions. Perhaps this will help you. VY 73. lane
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W9BVG
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« Reply #2 on: September 24, 2017, 10:44:24 AM »

KD8IIC-

I should have specified that the Davis line I have is the 300 ohm type. A company rep I spoke with said the punching machine is designed to leave those ~3 in. sections of polyethylene intact. I don't remember if he said Davis' 450 ohm line is also produced with the un-punched sections or not. With ~180 ft. of line to my antenna, I don't think I want to tackle removal of all those bits of poly (!). Still, I appreciate your reply!
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KD8IIC
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« Reply #3 on: September 25, 2017, 05:09:59 AM »

  Perhaps alternative would be using the open wire variety pre-made. 3-3/4 inch spacing.
  It has held up vy well for me. vf 92 I think
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N3QE
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Posts: 5026




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« Reply #4 on: September 25, 2017, 06:18:12 AM »

I think the same stuff is available under different brand names but it's all the same manufacture.

I wonder if there's some technical reason why the punching pattern is syncopated to begin with.

Maybe there's some problem with behavior in the wind if you make the pattern too regular? Like how marching can destroy a suspension bridge. https://en.wikipedia.org/wiki/Broughton_Suspension_Bridge

I use the stuff in many places indoors and on the side of the house but not for any long stretches in the wind (I've gone to polycarbonate rod spacers on my long airborne stretch because even with occasional twists the ribbon line turned into a sail.)
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