Ed wrote:
Actually, significance is based on the frequency of operation, as you
just indicated. Since the original poster was talking about an aluminum
jacketed heliax, I assumed the pertinent frequencies to be at least VHF,
if not higher; which would make the difference between the foam dielectric
RG-8 and solid dielectric RG-8 signifacant!

I'm moving to a new QTH and have only kept up
with this thread sporadically. I have now gathered
that the point is that it's not the foam per se
that has the largest effect, but the larger center
conductor required to bring the impedance back
to 50 ohms. Consider the fact that the 9913 center
conductor is #10 while the RG-213 center conductor
is #12.
--
73, Cecil http://www.w5dxp.com