Ron:
The Mt Arlington station is on the NJ Transit Morris & Essex, and Boonton lines.
On the Database, the frequency can be found in >>> New Jersey/Morris/Statewide/Railroads)/NJ Transit/Hoboken Division.
On the HP-1, NJ Transit trains are under the "Railroads" tag, along with Amtrak and CSX.
The freq is 161.400.
JM
PS> Took me a while to figure this out, and create a Favorite for it.