Bob,
Have just wound a coil on 4" grey UPVC, but before I did I whacked it into
the microwave, and it certainly didn't show any signs of warming.
Maybe they have removed the carbon?

73
John
VK2KC
"Bob Bob" wrote in message
...
Hi John

As I remember too if you use plastic conduit (in VK) the orange stuff
has no carbon but the grey stuff does. ie it has carbon mixed in when it
is extruded.

I don't know how good that info is, it's comes from way back in
anecdotal land. I just assume grey stuff is not to be used for radio
antenna system!

Not directly on topic but may be related.

Cheers Bob VK2YQA

VK2KC wrote:

My question is, does carbon fibre absorb RF?

VK2KC wrote:
Bob,
Have just wound a coil on 4" grey UPVC, but before I did I whacked it into
the microwave, and it certainly didn't show any signs of warming.
Maybe they have removed the carbon?



basically, RF loss is not a controlled parameter for manufacturing.
Sometimes it might be fine, other times not.

The Tesla Coil builders use lots of PVC pipe as coil forms (as well as
things like cardboard concrete forms: Sonotube(r)) and there is huge
variability in dielectric strength. I would imagine that RF loss also
varies substantially.

If you're really obsessing, the loss varies quite strongly with
humidity. PVC readily takes up and releases moisture from the atmosphere.

Hi Jim

Even 101 nylon has a problem like that. When you machine it after its
been sitting on the shelf for a few months you find the diameter has
increased from water absorbtion.

Cheers Bob


Jim Lux wrote:


If you're really obsessing, the loss varies quite strongly with
humidity. PVC readily takes up and releases moisture from the atmosphere.

Tnxs John

Good to know...

Cheers Bob VK2YQA

VK2KC wrote:
Bob,
Have just wound a coil on 4" grey UPVC, but before I did I whacked it into
the microwave, and it certainly didn't show any signs of warming.
Maybe they have removed the carbon?