I am trying to reconcile the following in respect of for practical low
loss RF transmission lines:

In the RLGC model for Zo and gamma, it is generally accepted a good
approximation is that R=c1*f**0.5, G=c2*f, and L and C are constant.

If the term (G+j*2*pi*f*C) can be rearranged as
(2*pi*f*C(G/(2*pi*f*C)+j)), and substituting c2*f for G, written as
(2*pi*f*C(c2/(2*pi*C)+j)).

If we regard G to be principally the loss in the dielectric , then
c2/(2*pi*C) should give us the dielectric loss factor, D, 1/Q,
tan(delta), dissipation factor, power factor, whatever you want to
call it.

alpha= 0.5*R/NomZo+0.5*G.NomZo
It also seems generally accepted that Matched Line Loss (MLL) can be
modeled well by the expression MLL=k1*f**0.5+k2*f.

(Remember that alpha= 0.5*R/NomZo+0.5*G.NomZo)

It follows then that c2=k2/(10*log(e)*Ro), and that (G+j*2*pi*f*C)=
2*pi*f*C(k2/(10*log(e)*Ro)/(2*pi*C)+j) which implies that D is
k2/(10*log(e)*Ro)/(2*pi*C).

Problem is, that whilst PE has D somewhere about 2e-5 up to 1GHz, the
loss model for RG58CU (PE dielectric) indicates D 2e-3 much much less
than would be expected from D of the PE dielectric alone.

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
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