Hi there: You can also do some of this by simulation using the magnetics calculator on the K & J Magnetics web site as a starting point for your testing. How do you decide what magnetic field strength is required for a selected width of aluminum tape? ...regards Michael
This should help. jer
http://www.diyaudio.com/forums/planars-exotics/50162-another-diy-ribbon-thread.html#post571024