I am a newbie wanting to set up a base station at my house on top of my
tv tower. I am interested in building one myself. I have the capability
to weld.

Do the j poles have gain to them? Are they near the performance of a
several element yagi?

Can I make a dual band antenna in each of these styles?

Do the copper j poles last many years? I sometimes have high winds and
lots of rain. Plus, I dont like heights and only want to do this once.

I would ideally like to reach a repeater about 70 - 80 miles away from
me.