"Owen"
Any thoughts. Is there an inconsistency between the explanation that
G
is principally due to D of the dielectric material, or I have I
messed
the maths up?

Owen
===================================

From where did you obtain D 2e-3 for RG 58 ? That's the most likely
source of the discrepancy.

Also the highest grade polyethylene is unlikely to be used for the
manufacture of RG58.

The only way to investigate is to lay 100 feet on the ground, in the
form of a circle, and measure attenuation vs frequency between the
ends from 1 MHz to 1 GHz.
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Reg