[TowerTalk] NON-INSULLATION STRIKES AGAIN! RG174 ANOMALLY

[Larry - K7SV]

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