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.

Roy Lewallen wrote:
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?

That's right.

More important, didn't he say he is matching 35 ohm elements in a
vertical array. I'd think mutual coupling would cause much bigger
errors than the cable unless he is feeding the elements either at 0 or
180 degree phase. Why worry about Vf and cable impedance when the
lements are all over the place in impedance?
:-)

73 Tom