In digging around looking for good deals on parts etc. I ran across this guy's website. He has an excel spreadsheet calculator for getting the impedance of an AM tower. Might be interesting for the few of us with 160 m. insulated towers:
Scroll down to find the link
http://www.jimpollock.net/There are a few other files in there pertaining to antenna tuning units and stuff that might be interesting, expecially if you have a lot of antenna technical knowledge (which I do not -- i'm just the information mule).
Rob
