Dan,
I do not have a 326 MKS but I do have a 2011 293SAB. When I hook up park cable to my docking station, I have to turn off my antenna booster (little red light mentioned earlier). If that does not work, you probably will have to trace the signal. They make a "pinger" to send a signal while you trace it with a multimeter but I just used a long length of coax cable and tested for continuity. Let us know how you make out.