[TowerTalk] LMR 400 VS 9913?

[w8ji.tom]

Hi Press, 

> the voids in the braid. Thus either coax can suck oxygen, water, or what
> have you if the connector is sealed improperly. The hardline has only the
> voids or bubbles in the foam, making it less at risk, but poor sealing at
> the ends will still cause trouble through gas and vapor ingress. 

I'm a little puzzled by the worry about oxygen and the dielectric. 

I understand oxygen contaminates the surface of metals, forming lossy
layers of oxides (except with silver) that might increase loss a tiny bit
at HF and more as frequency is raised. Corrosion also increases loss
dramatically (even at HF) if one or both conductors in the transmission
line are braided.

I had no idea oxygen contaminates dielectrics, or that DRY dielectrics are
a major  loss mechanism in coaxial lines. Last time I looked at the
problem, the bulk of loss was in the conductors (at least at frequencies
below 200 MHz I am interested in).

Am I missing something?

73 Tom




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