there was a coax cable provided with the empennage kit--unless it comes with one of the other kits. It runs from the transponder hole in the tail cone to the panel (see 10-23--WH-00014). From what I understand, the phone wire runs to the ELT. At least my ELT has no way to connect a coax cable.
EAA Chapter 1093 member
RV-14a (serial number 140073)
N73XP (at least that # reserved now)