The linkage between your TravelSat and Sony receiver is probably not from 9pin Travel Sat port to another data port but instead to the telephone jack on the back of the receiver. I have a friend with a TravelSat who has lost his cable of that description. I would make a suitable cable for him except we havent been able to find a wiring diagram that would tell us which pins on the DB9 plug are connected to the phone plug, (which probably uses only the center two of the four pins on the phone plug.)
Unfortunately, that's all I can tell you and it's not much help.