On Sat, 4 Dec 2004 08:35:56 +0000 (UTC), Stewart Pinkerton
wrote:

On Fri, 03 Dec 2004 21:33:50 GMT, (Don Pearce)
wrote:

On Fri, 3 Dec 2004 18:22:28 +0000 (UTC), Stewart Pinkerton
wrote:

On Fri, 03 Dec 2004 15:26:46 GMT, (Don Pearce)
wrote:

On Sat, 04 Dec 2004 02:17:42 +1100, Patrick Turner
wrote:

Two things:
Teflon is not a great dielectric - why would you do this?

Teflon's Dielectic Constant is actually quite good, really, go look at the DC
tables.

What on earth is a "good dielectric constant"? And it is nothing to do
with Er that makes teflon poor, it is the charge retention.

Ahhh. I was as puzzled as Patrick by your remark, as Teflon is
generally regarded as just about the *best* dielectric for caps and
cables. Charge retention, while the bane of the sample/hold designer,
is simply not an issue with a conventional a.c. signal.

Mechanically it is hard to handle, and electrically it is actually not
as good as polypropylene. There isn't that much in it, though.

Mechanically it is vastly superior, as it doesn't melt when the cable
or capacitor is soldered! Electrically, it is significantly superior
to polypropylene, which is why it's used in microwave gear such as
semi-rigid coax. Where are you getting your information?

Can't remember is the problem. This stuff has been swimming around my
brain for a few years now, but I can't for the life of me remember the
source. I just remember being surprised at the results, and looking
fairly critically at the tests that determined them.

d

Pearce Consulting
http://www.pearce.uk.com