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
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