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Re: [TenTec] Transmission Line Names

To: tentec@contesting.com
Subject: Re: [TenTec] Transmission Line Names
From: "k3hx@juno.com" <k3hx@juno.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Fri, 3 Feb 2006 13:45:12 GMT
List-post: <mailto:tentec@contesting.com>

I thought that ladder line was called that, because it is two parallel 
wires, with their spacing maintained by insulating rods of ceramic, 
polyethylene, paraffin soaked doweling or other plastic material. It 
looks like a miniature rope ladder. How does open wire feeder differ 
from ladder line? Or is it another name for the same thing?

>>I've always heard this type of line refered to as "ladder line" 

although there was a parallel wire line made with horseshoe-shaped 

clear polystyrene insulators with the same name.  (early 1960's)

I thought that window line was essentially jumbo sized TV twinlead, with 
rectangular holes punched in the flat polyethylene (or other plastic) 
separating dielectric material the maintains the spacing between the two 
wires. Is that the correct? Most of what I have seen, that I thought was 
called window line, is dark brown or black.

>>Me too.

By TV twinlead, I am referring to the 300 ohm flat "ribbon cable" that 
was commonly used for TV antennas, before coax became the norm. Often 
AM/FM Stereo receivers or tuners would be supplied with a folded dipole 
made out of this 300 ohm ribbon cable. It is usually translucent white 
or dark brown or black.

I have also seen variations of  TV twinlead, which instead of having a 
flat section of plastic between the two wires, have a round or 
elliptical cross section piece of foam between the wires. What is that 

>>In a former life, I put up TV antennae.  We called this type of line

 "tubular twin lead."  Belden made a version of this that was nearly

indestructible.  I've re-used 20+ year old lengths of this line on 

replacement antennae.  Amazing stuff, saved the customer some $$

And there is another kind of twinlead, which looks a bit like large zip 
cord, or telephone service drop wire. What is that called?

>>I think this is "75 ohm" twin lead.

In order to have an intelligent discussion, we need to understand what 

we mean by the words we use.

>>Well stated.  We should all come to an agreement on what terms we use 

to describe the same object or process.


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