Roy is right. You must meaure your cable to be sure.
The stuff I have now calculates to .73 using a regular MFJ analyzer.




Roy Lewallen wrote:
My experience is that the velocity factor of foam dielectric cable like
RG8X varies considerably from batch to batch and manufacturer to
manufacturer. Apparently they have poor control over the foam density in
the manufacturing process. For any application where it really matters,
you really have to measure it for the particular piece of cable you'll
be using.

Roy Lewallen, W7EL

AK wrote:

Is 78% the correct velocity factor for RG8X coax?