I dunno about the frequencies for Richmond to DC but here is DC to NYC:
DC to CP-Morris, Division post (on the other side of the Delaware River from Trenton NJ): 160.920
CP-Morris to NYC (frequency used as far north as New Rochelle NY): 161.010
Also, NJT lines that connect to the Northeast Corridor use 160.235. These lines include the: Atlantic City Line (connects at CP-Shore, in North Philly), North jersey Coast Line (Connects at CP-Union in Rahway NJ), and the Raritan Valley Line (connects at CP-NK just south of Newark NJ Pernn Station. Its really making a connection off of the Conrail Lehigh Line, as the RVL tracks connect to, and use this line, from Aldene NJ to Newark.)
Hope this helps and enjoy your trip!