Agree about the concern for connections, but I still say you're making a
bad generalization ... in this case based on anecdotal evidence. The
green patina seen on that copper tubing is very probably highly porous
(I have experience with it since I taught myself how to create it for a
different project), which means it provides a very tortuous path for
current flow that would greatly increase it's resistance beyond the
simply bulk conductivity of whatever form of copper oxide is there.
That would make it more like an insulator instead of simply a lossy coating.
We're probably splitting hairs here, but from a purely technical point
of view it's not correct to say that the surface condition never matters
except for the connections.
Dave AB7E
On 10/14/2016 7:50 AM, Jim Thomson wrote:
### KM1H used cu tubing for his .25 wave strip lines in his 144 mhz tube amp.
The cu tubing has since turned green. Amp was built
a long time ago. Zero effect on BW or PO or gain. Amp was built > 25 yrs
ago. As long as the terminations at each end are good, you wont have any issues.
Its when you have bad connections from corrosion or oxidization that u start
having problems
Jim VE7RF
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