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.


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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