There is no bulkhead adapter for the radar cable. You'll need to purchase a thrudeck wiring clamp (has a rubber insert in it that locks around the cable to prevent water from weeping through the deck). If possible - I would put a pipe up through where the center of the mast sits so you could run it through it and down below. There is no really "visual appealing" method of running the radome cable on a mast stepped mast unfortunatedly. On my C-27 I ran it out the side of the mast and then punched a huge hole in the deck in the head and ran it down that way. I am sure others will pipe up...You may want to post on the Catalina Owners Website where you'll get some good info / feedback as well...