> Where did you read that Amphenol used PTFE?
> I have never heard of that.
> BTW, PTFE is never clear, AFAIK.
> Rick N6RK
Right. Real amphenol UHF elbows (83-1AP) use polystyrene dielectric. It is
clear. The dielectric constant is 2.56, which is better than bakelite but
not as good as teflon as far as keeping the Z0 close to 50 ohms.
Amphenol PL-259 *connectors* are available with several different
dielectrics including teflon. Of all of the common dielectrics, teflon is
the best for UHF connectors, and results in a Z0 of about 45 ohms.
Dielectrics that have found their way into cheap UHF connectors include
Delrin, nylon and other thermoplastics which almost always have higher
dielectric constants, and thus yield a poor(er) match, in addition to also
often not being heat-resistant.
For whatever it's worth, if you could use air as a dielectric in a UHF
connector, the Z0 would be very close to 50 ohms. Occasionally you'll see
some UHF female connectors with air dielectric on some pieces of equipment -
some of the power/SWR meters that Diamond makes comes to mind as an example.
A buddy of mine, Al Crites WA9ZZU, worked for Amphenol and did R&D on UHF
connector dielectric "beads" a long, long time ago. Some of the info above
came from him.
--- Jeff WN3A
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