Hi Mogens,
Basically you could use either port, but note the following:
- COM2 is normally used for CAT. If for some reason you don't want to run CAT, you can use COM2 for another device such as the amp.
- COM1 is wired differently from COM2 (essentially "backwards"). Look at the manual carefully for the pinout if you choose to use COM1.
73,
Mitch DJ0QN / K7DX