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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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