[TowerTalk] Current choke beads

Joe Reisert, W1JR W1JR at arrl.net
Sat Jul 28 17:33:41 EDT 2007


Hi Ian,

Great to hear from you. Was thinking of you and Nadine when we heard 
about all the flooding in Oxford. That was a great visit with both of 
you. I'll bet you're glad you're not there now!

Thanks for jogging my memory and the great rundown on those 
dielectrics. Over 15 years has passed since I worked on UltraLink and 
we don't always remember all the minute details, especially as we get 
older! What I meant to say was FEP (which it wasn't anyhow), not 
PTFE. Obviously PTFE and Teflon are the same. I checked both the 
Cushcraft and Tessco websites and they verified that UltraLink Mobile 
indeed used Teflon (RTM) as the inner dielectric. I see that they now 
have white jacketed available. The part number for the black jacketed 
coax I referred to is now listed as TL92887. So, it may be of 
interest to anyone needing a low cost high power coax for baluns.

Sorry for the mistake.

73,

Joe, W1JR

At 05:35 AM 7/28/2007, Ian White GM3SEK wrote:
>   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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