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Re: [TenTec] Balun Isolator

To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Subject: Re: [TenTec] Balun Isolator
From: "Ronald C. McConnell" <rcmcc@embarqmail.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Fri, 9 May 2008 12:46:10 -0400
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Coax braid has a shielding rating,
such as 95%, meaning that 95% of the inside 
shield current should stay inside
and maybe 5% might escape to the outside.
Likewise, currents on the outside 
coming from whatever source has 5% access to the inside.
Some cheap coax has much less shielding coverage.
High grade coax is sometime double-braided.

Cable TV coax with solid foil shielding _could/can_ do better.
The coax used by the cable TV companies looks pretty good.
In the mid-1990s while figuring out what "Joe-Six-Pack"
might use to cable up his home for an extension
of the proposed-at-the-time hybrid fiber/coax
telephone network system, we bought some
TV cables, connectors, splitters, etc.
off the shelf of a big chain home supply store.
We built a sample home system in the lab.
The signals died in less than 30 feet.  
Huh !!??
_Then_ we measured the cables.
One of the gang dubbed the stuff "Death Cable."
Later I measured the DC resistance at one ohm per foot.
I didn't measure the shielding,
but it looked really bad physically in an autopsy.

Don't claim to be an expert on coax,
and surely someone on the list can give the full story
or a web link to a ham site or Belden or other manufacturer.

Cheers, 73,

Ron McC.

Haruspex on duty.
Appointment not necessary. 

Ronald C. McConnell, PhD

 WGS-84: N 40º 46' 57.9"  +/-0.1"
         W 74º 41' 21.3"  +/-0.1"
         FN20ps.77GU96 +/-
         V +5058  H +1504


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