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Old 6th Oct 2018, 8:06 pm   #15
terrykc
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Join Date: Nov 2010
Location: North Hykeham, Lincolnshire, UK.
Posts: 515
Default Re: Determining Zo for coax cable

Quote:
Originally Posted by G8HQP Dave View Post
Foamed or semi-air-spaced may be around 1.5, solid poly around 2.
Yes Dave. I took Webro's data for WF100 - centre conductor 1mm, inner dielectric diameter 4.8mm, so D/d = 4.8, took the log and multiplied by 138 then divided by 75 and squared the result which was 1.57.

Strange that you don't seem to be able to find the relative permeability figure for foamed PE in any table (well, any that I could find) but solid PE is usually stated at around 2.2.
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