This system is a Trimble 500 with RTK hooked up to a Nav 2 controller.
The RTK radio comes in on the 9-pin com port. The circular com port or AUX port is hooked up to the Nav
2.

In the setup screen for NMEA output it doesn't let you pick which COM port to program the MMEA. out. It does if you are just using Omnistar but when hooked up to Nav 2 this is not an option.

Since both ports (9-pin and circular) are tied up, do you use the laptop port for the NMEA output?

If so, does it use a Null-modem cable or straight through cable?