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

jpk5lad at cox.net jpk5lad at cox.net
Mon Mar 24 16:15:24 EDT 2014

>From where I'm sitting, I can see a run of Kilowatt Twinlead running up the wall, into the attic 
and to standoffs going up the tower.  I've used it for years to feed two of my top guy anchors, 
insulated off to be fed at the top.  This KW twinlead was not 75 ohm but was actually 300 
ohm.  When I owned a ham store in the 70s, I bought it from Dentron in a 100' length.  
Dentron offered both the 450 ohm window line and the 300 ohm KW Twinlead through their 
I do remember (I'm from the 1957 era) both a lighter duty 75 ohm twinlead and a much, 
much heavier 75 ohm twinlead although I don't recall ever using it.  Perhaps they were both 
spec'ed at 72 ohms, it's been too many years to remember that particular detail.

Around our neck of the woods, I believe only the 300 ohm heavy and thick twinlead was 
referred to as "Kilowatt Twinlead."

Just musings from another old timer.

Jim - K5LAD

On 24 Mar 2014 at 12:45, Jim Brown wrote:

> 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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