[TenTec] 75 Ohm twin velocity factor ?

[Stuart Rohre]

While many 50 ohm coaxes are in the Velocity factor range of 0.66, twin lead 
lines typically are 0.98.

There are procedures to use an MFJ Antenna Analyzer to measure the exact Vp 
of any line.  Running on batteries, you can do this for twin lines to better 
than ball park figures.  I think these instructions for the MFJ use are on 
line.  Google Search "MFJ 259 Instructions"

Stuart
K5KVH