>
>
> >Solid dielectric is much more controllable, but I even measure the actual
> There ARE foamed dielectric coaxial cables that are extremely consistent
> and stable. For instance, Gore makes coax with foamed PTFE dielectric, and
> it's used for network analyzer test port cables.
>
> Most PTFE cables also have a discontinuity in their phase shift/dielectric
> constant vs temperature curve, unfortunately, right around 15-20 C (room
> temperature).
>
> However, the stable foamed, low loss stuff is wretchedly expensive, and I
> can't imagine a ham using it unless they happened on a spool of the stuff
> surplus.
>
> Jim, W6RMK
I would add that the Gore types have a very 'air-filled' Teflon tape
dielectric that is very soft. It is so hard to keep coaxial that most of
the good stuff requires armor to keep it working well. A cable of one meter
can run over $500! One squeeze or tight bend and that's it! There are other
Teflon tape dielectrics that are very dense by comparison and more difficult
to damage with typical ham handling. Not phase stable, though. And, big
bucks but less than the phase stable types.
Al, N6TA
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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