[TowerTalk] 75 or 70 Ohm twinlead or ladderline cable - does it exist?

[Jim Brown]

On 3/24/2014 11:36 AM, Drax Felton wrote:
> It's 72 ohm twin lead.  Also known as zip line.

That's a new one on me, and I've been at this since 1955. Back then, and 
for several decades thereafter, Belden and Amphenol made a product 
commonly called "Kilowatt Twinlead," which was a pair of AWG #13 
stranded copper conductors spaced apart by 2-3 conductor diameters by a 
rather beefy dielectric. My old Belden catalog from 1971 says it's part 
number 8210, is 72 ohms Zo, 0.67 Vp. I actually have several hundred 
feet, what's left from a 250 ft spool that I bought "new old stock" at 
the Milwaukee hamfest sometime in the 70s, figuring that I'd someday 
find a use for it. 25 years later, I did, and it fed an 80/40 dipole 
that I also loaded as a Tee vertical on 160M.

I also have some junk lengths of the Amphenol product, which looks a bit 
less robust.  Both products have been discontinued for several decades.

Last I looked (about 7 years ago), I think I remember DXE was selling a 
window line that they described as 100 ohms.

73, Jim K9YC