Owen Duffy wrote:

Very well done Greg.

Hopefully, in the fullness of time, you will roll all this information
into the web page.

I have read articles on issues with control of the foaming of
dielectric during manufacture, it seems more difficult to control than
all of the aspects of conventional solid PE dielectric line, so it
leaves one wondering if that may be the cause of the apparently low Zo
(~43 ohms) that you observed. If so, is it a batch to batch variation,
variable along the line (although your charts don't suggest that),
aging, temperature, migration of the centre conductor on the roll,
etc?

Well done OM.


I've measured a lot of cable over the years, and have found considerable
variation of velocity factor from batch to batch of otherwise identical
cable from the same manufacturer, as Owen's articles imply. Assuming
that the physical dimensions of the cable stay the same, Z0 will also
vary with foam density.

The piece of BuryFlex I have measures right at 80% velocity factor, and
very close to 50 ohms. I believe I'm within a percent or two on VF, and
an ohm for Z0.

Roy Lewallen, W7EL