[TowerTalk] NON-INSULLATION STRIKES AGAIN! RG174 ANOMALLY

[Neal Campbell]

Could be why it was being sold at Mendelsons!

Neal Campbell
Abroham Neal Software
www.dxbase.com
www.abrohamnealsoftware.com
www.sdrsystems.com
(540) 242 0911

Amateur Radio: K3NC
Blog: http://www.abrohamnealsoftware.com/blog/
DXBase bug reports: email to cases at dxbase.fogbugz.com
Abroham Neal forums: http:/www.abrohamnealsoftware.com/community/

DX Cluster: dxc.k3nc.com port 23





On Fri, Sep 4, 2009 at 6:55 AM, Larry - K7SV <k7sv at comcast.net> wrote:

> Some of you may remember my posting about our experience with beverages
> using plastic boxes to house matching transformers. The black plastic boxes
> turned out to be conductive which obviously led to a lot of head
> scratching.
>
> Well, I've been working a small project using RG-174. I kept finding shorts
> after putting connectors on the ends. Nothing was making sense so it got to
> the point that I cut a foot long piece of the stuff, stripped back about an
> inch of the outer insulated jacket at both ends and pushed the shield away
> from the ends. I then took resistance measurements between the shield and
> the ends (didn't strip back the inner insulation, just stuck the meter
> probe
> in the end). So I'm still seeing resistance between the shield and the
> center conductor.
>
> On a whim I connected a meter probe to the inner "insulation" at both ends
> of the piece. Sure enough it was a conductive material. I picked up a
> couple
> hundred feet of this stuff from Mendelson's at Dayton a few years ago. As
> it
> turns out construction consists of an insulated black outer jacket,
> stranded
> copper shield, a black conductive material, a light opaque insulation and
> then the stranded copper inner conductor.
>
> My problem obviously existed anywhere that the inner black "insulated"
> material was touching the shield.
>
> This is the first time I've experienced something like this with RG-174.
> Actually as I think about it, the stuff must have really great isolation
> between the center conductor and the braid! I don't think this is typical
> RG-174!
>
> 73 de Lar K7SV
>
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