Hi,

I've noticed most homebuilt amateur antennas use tubing and usually
copper,
whereas commercial antennas typically use round bar, either steel or
Aluminum.

I understand the advantages of the materials in terms of electrical
conductivity and weather resistance,
however I dont understand the pro's and cons of using tube vs round
bar? Can you point me to
a book that may discuss this?

Have studies been done re the effect of a layer of oxidation on the
performance of the antenna?

Finally, there is plenty of material about designing antennae for a
band, but every little about designing it at a particular impedence,
can you point me to a discussion on this too?

Thanks

Steven