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Re: [TowerTalk] 75 or 70 Ohm twinlead or ladderline cable - does it exis

To: towertalk@contesting.com
Subject: Re: [TowerTalk] 75 or 70 Ohm twinlead or ladderline cable - does it exist?
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Mon, 24 Mar 2014 12:45:23 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
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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