The early comm satellites that went up used Teflon as a substrate for the
RF boards. Teflon doesn't do too well in a radiation environment. The
MTTF of the first satellites was weeks due to the RF portions literally
turning to dust. It was a hard lesson, but we learned quickly that Teflon
was not the appropriate substrate for RF circuitry on orbit in the van
Allen belts which were just being discovered at the time. However, its
great here on earth above some 500 MHz due to its low loss at microwave
frequencies and homogeneity of its dielectric constant. Nor is it as
dispersive as FR-4.
Dave - WØLEV
On Tue, Jan 21, 2020 at 8:47 PM K9MA <k9ma@sdellington.us> wrote:
> Back in my spacecraft hardware building career, it was well known that
> Teflon would "cold flow". Great care was taken where wires went around
> corners, etc., that there was no pressure on the insulation. Has anyone
> heard of such issues with chokes?
>
> 73,
> Scott K9MA
>
>
> On 1/21/2020 12:21, Jim Brown wrote:
> > On 1/21/2020 9:32 AM, EDWARDS, EDDIE J via RFI wrote:
> >> Use coaxial cable when making RF chokes for antenna systems.
> >
> > Parallel wires work fine for winding chokes. There's no need for
> > shielding -- the field from the choke is confined to the core.
> >
> > At least half of the chokes in my station are wound with a pair of
> > Teflon insulated #12 stranded silver-coated copper wire. The rest are
> > wound with RG400. The Cookbook includes data for #12 THHN as a lower
> > cost alternative.
> >
> > http://k9yc.com/2018Cookbook.pdf
> >
> > 73, Jim K9YC
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
>
>
> --
> Scott K9MA
>
> k9ma@sdellington.us
>
> _______________________________________________
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> http://lists.contesting.com/mailman/listinfo/rfi
>
--
*Dave - WØLEV*
*Just Let Darwin Work*
*Just Think*
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