Topband: Cable shields

[DAVID CUTHBERT]

Tom, I don't doubt that you performed the cable TI measurement correctly
but I have seen folks take data that is actually the TI of the test fixture
and not the cables under test.

What TI impedance did you measure?

Dave WX7G
On Jul 11, 2012 2:37 PM, "Tom W8JI" <w8ji at w8ji.com> wrote:

> The statement CATV coaxial cables or cables with foil/drain shields do not
> have good shielding, because of transfer impedance and high resistance, was
> made a while ago here on this reflector. I think the statement was those
> shields are not good at MF or HF.
>
> This past weekend, I modified a test fixture to test sample cables for
> common mode.
>
> I compared two samples. One was an 8-foot long sample of two-year-old
> CommScope F6 dual-shield, and the other was a heavy copper braid RG6/U
> solid
> dielectric that was inside. The F6 was pulled out from a cut cable a week
> ago, one bonded foil overlaid with aluminum braid.
>
> The cables were within a dB or two of each other.
>
> http://www.w8ji.com/coaxial_cable_leakage.htm
>
> 73 Tom
>
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