On Sun, 09 Apr 2006 18:02:28 -0700, Roy Lewallen
wrote:

Owen Duffy wrote:
. . .
Reg's response is interesting, I draw the conclusion that a 'quick and
dirty' confirmation of quality of a foam cable is whether its measured
VF is close to spec, it is it off, so is the Zo likely to be off.

I don't agree that this is a good test. The Z0 of cables with solid PE
insulation varies considerably, and it's doubtful that the variation is
due to variable dielectric constant of the solid insulation. So why
should we assume that Z0 variation in foamed dielectric cable is due
solely or mostly to the dielectric density?

The thinking is more the case that the foam density / dielectric
constant is apparently very hard to control, and in cheap cables with
poor QA, a probably source of failure to meet spec.

Owen
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