Roy Lewallen wrote:
The velocity factor of 300 ohm ribbon twinlead is approximately 0.80,
but it varies from brand to brand and lot to lot.

I measured the VF of 300 ohm and 450 ohm window-line from
The Wireman. The 300 ohm stuff was very close to 0.8 while
the 450 ohm was closer to 0.9
--
73, Cecil http://www.w5dxp.com