MON adds four new SSVs: VL and VH for VORs; DL and DH for DME. There's range changes in VOR, DME, and VORTAC.

See AIM 1-1-8. NAVAID Service Volumes https://www.faa.gov/air_traffic/publications/atpubs/aim_html...

"documented network of airports" is a poorly worded reference to MON airports as distinguished from MON navaids.