Marek,
Glenn just answered on the "ATU-10" thread. It really is neat how David Fainitski, N7DDC, designed the ATU-10 to only require programming the PIC 16F1454 and that code links to the PIC 16F18877 main microcontroller to load programs using your PC USB port for the initial firmware and future firmware changes. WAY better than the ATU-100 implementation with the PIC 16F1938.
Wire size of #22 or #24 is fine. I happen to have a junkbox spool handy of #22 for the BN43-1502, so I used that..
73 Kees K5BCQ