On 5/7/16 7:01 AM, Richard (Rick) Karlquist wrote:
On 5/6/2016 6:36 PM, Don W7WLL wrote:
After reading specs that the Amphenol used PTFE
(all of my Amphenol of a later vintage appear to be clear insulation)
Don T
Where did you read that Amphenol used PTFE?
I have never heard of that.
BTW, PTFE is never clear, AFAIK.
PTFE is usually a solid white
a sort of translucent clear is often polyethylene (or high density PE) -
low melting point, but no halogens, so burning it is like burning wax,
you'll see this in "plenum rated" cables, because it doesn't create a
toxic smoke hazard when a building catches fire
Phenolic - a thermoset plastic (e.g. Bakelite, it's been around for over
a century) which usually has a filler (wood in the case of Bakelite).
I've seen UHF connectors with a phenolic fabric dielectric (you can see
the weave), it's probably linen for the fabric, since that's what was
used for "precision" components. Circuit board material (XXP, for
instance) used paper as the filler.
Diallyl Pthalate is a popular dielectric - it's rugged, but I don't know
if it's used much in RF connectors - typically it's blue or green, in
connectors like Submini D. It's also used in high voltage connectors.
Connectors which use phenolic often have an "upgraded" version using
Diallyl Pthalate.
There's been changes in manufacturing since the UHF connector was
introduced pre WW-2
https://www.google.com/patents/US2422982
https://www.google.com/patents/US2335041
Back then, you'd machine stuff and assemble it.
Now, injection molding and form in place might be more common - it's a
LOT cheaper.
PE is trivially injection molded - Phenolic is "machine and assemble"
PTFE can be sort of molded: they sinter a powder in a mold, but you
can't injection mold it.
In any event, PTFE is greatly inferior
mechanically, and has no electrical
advantage at HF, or even UHF. It's
high temperature rating is also of no
consequence for most ham applications. I
don't know why any knowledgeable person
would even want it, except in some
corner case like a common mode choke
made with PTFE coax.
Rick N6RK
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