[TonyJSenior]

I don't have a 41-220, but it looks similar to a 40-120 that I do have. The 40-120 has a loop antenna with some windings that serve as an 'electrostatic shield' supposedly. If the 41-220 used this same antenna, this website details on how the antenna and taps are constructed:

http://www.geocities.com/reevesradios/150a.html

Hope that helps!

EDIT: Looked at the print for a 41-220 and don't see the taps referenced at all. The antenna is probably different - sorry!