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Old August 3rd 06, 02:03 PM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Jul 2006
Posts: 137
Default Question on carbon fibre fishing rod

Probably not carbon fiber tho, right?

I doubt it's possible to make a carbon fiber pole without end-to-end DC
continuity. It could be high resistance, but I think you're always
going to have fiber-to-fiber contact along the whole length of the
pole.

Carbon fiber, just as a point of general information in this thread,
seems to have about 800 times the resistivity of copper according to
matweb.com, and about 20 times the resisivity of 304 stainless steel.
Not something that will make for a great radiator.

If you assume fairly low frequency such that the skin depth in carbon
fiber is deep enough that current will flow uniformly in a 1.6mm (1/16
inch) tube wall, and uniformly in a 1mm wire, you need a 10cm (4 inch)
carbon fiber tube to match the 1mm wire in conductor loss!

Interestingly enough, I read recently (I don't remember if it was QST
or on the web) about someone who was using a fiberglass fishing pole
for a vertical antenna and had significant detuning problems until they
moved the wire far away from the pole. I, on the other hand, built a
center loaded 40m antenna on a pair of fiberglass poles and it tuned
exactly as one of Reg's programs and EZNEC said it would, suggesting
that my poles are fairly good insulators.

I still think I'd like a carbon fiber fishing rod... sounds nice and
strong. Maybe it's best used as center supports for inverted vees and
the like, and for carefully considered vertical applications.

Dan

My South Bend Sunny Day SD-20 pole doesn't show any DC
resistance even when the paint is scraped off.
--
73, Cecil http://www.qsl.net/w5dxp


 
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