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Questions about a 2m J-pole
Dave Platt wrote:
In article , Highland Ham wrote: My question is directed to the different grades K,L and M ,whether any particular grade would give better RF radiation performance . It could be that the grade with the highest copper content gives the best performance ,although I doubt that it will be measurable. My recollection is that the basic difference between the various grades is the thickness of the copper walls. The thicker-walled pipe is what's preferred for outdoor/buried use and/or higher pressures (e.g. use on the supply side of a house's water-pressure regulator). RF current flows only through the skin of a conductor... it doesn't penetrate very far into the body. One web calculator I found says that the skin depth of a 144 MHz signal in copper is around 200 micro-inches, or 1/5000 of an inch. If the tubing wall is much thicker than this, the additional thickness will have no significant benefit in reducing resistive losses. Since even the thinnest-walled (Schedule M) copper pipe has a wall thickness which is about a hundred times more than the skin depth, there's no electrical benefit to using thicker-walled tubing (Schedule K or L). Unless there's some mechanical reason to want to use the heavier- schedule tubing, I'd just stick with Schedule M - it's lighter, less expensive, and should be plenty stiff and strong for most applications. ---------------- Go the cheapest way, as recommended above. You can't tell the difference between the various grades without laboratory grade measuring equipment. Surely no one receiving your signal could ever tell the difference. Ed, NM2K |
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