There are two types of frequencies for each vessel: a transponder (XPDR) and one or more docking systems. From
ISS XRPD you get a reception at < 1000 km, for docks it is < 100 km.
DGIV has no built-in autopilot, which can bring you to the station if you are more than 100 km from it. Some people
swear by Rendezvous MFD.