wrote:
>On 27 Jul 2007 at 16:03, Joe Reisert, W1JR wrote:
>
>< snip >
>
>> In 1989 I helped develop a low cost PTFE coax for the Cushcraft
>> Corporation. They needed a cost effective coax for installing mobile
>> antennas in automobiles that wouldn't melt if placed near catalytic
>> converters etc. Cushcraft marketed it as "Ultra Link" coax. Ultra
>> Link, as I recall, is about the diameter of RG58. It uses PTFE
>> (instead of teflon) dielectric.
>
>Hmmm. I was under the impression that "Teflon" IS "PTFE". I thought
>that Teflon was DuPont's trade name for PolyTetraFluoroEthylene. Am
>I wrong?
"Teflon" is a trade name, and can be used however its owners wish.
When PTFE was first invented, both names meant the same thing. But
DuPont have since developed a much wider range of related materials such
as FEP (fluorinated ethylene-propylene), all of which may be marketed
under the "Teflon" trade name.
PTFE is a chemical name that belongs to only one substance. In contrast,
FEP is a family of materials in its own right. At one end of the range
are materials with very little propylene in their makeup, which brings
them very close to true PTFE. Other grades have a lower softening
temperature (which makes them easier to process) while also being
tougher and more UV-resistant - just what's needed for a cable jacket.
If a cable is jacketed with a material that feels slippery like PTFE,
but is even tougher and also more transparent (true PTFE is white), that
is almost certainly one of the FEP family.
FEP is also used for the inner dielectric in some grades of coax, but
the softening temperature is lower than PTFE. This makes FEP less
suitable for cables that have to operate at high temperatures (or at
high power) and maybe also with a tight bending radius. So when
CushCraft were designing a new cable specifically for that kind of
application, it would have made complete sense to specify true PTFE.
--
73 from Ian GM3SEK
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