[TowerTalk] Best Coax

[Tom Rauch]

> The hard question about open wire line is - what to use for insulators?

I went through that two years ago, when I was installing a 1500 foot 
long open wire line. 

I bought UV resistant Lexan and mostly used it, but I also installed 
sample pieces of other materials of various types.

I have a bench punch, and was hoping to find a material I could pop 
holes in instead of drilling. No such luck. So I drilled and cut.

My line is number eight bare copper with 2.75 inch centers, 450 
ohms. Here's what the score is over a year later in the Georgia sun:

1.) The gray PVC surface powdered, and held water. It carbon 
tracked and failed by shorting.

2.) The white PVC is still OK, but breaks (cracks) easy.

3.) The regular Plexiglass? (I found a 4X8 sheet 3/8 inch thick  
along the road) cracks when stressed.

4.) The regular plastic fell apart.

5.) The nylon is still OK

6.) The UV resistant Lexan (1/8 inch thick) is still good, and never 
has broken. The #16 tie wires break before the insulator does. 
That's why I like it best.

By the way, I've melted both plexiglass and PVC in an open wire 
line (#16 wire) feeding two half-waves in-phase on damp days. Don't 
know if it was more of that surface powdering trapping dirt and 
moisture or what because the insulators just totally melted. 

I guess what someone uses would depend on what they are 
actually installing and how long they want it to last and how high 
the voltage is on the line.


  
  

   
73, Tom W8JI
w8ji@contesting.com

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