A search on digitalfrequencysearch.com for Montgomery county MD for NXDN frequencies yields listings of several CSX railroad frequencies ( 160.23, 160.32, 160.785, 161.145, 161.235, 161.355 ). In the RRDB, performing a search for Montgomery county MD for NXDN systems shows none of the CSX freqeuncies found in digitalfrequencysearch.com. Any insight into the difference between the sources? Would these likely be single frequency NXDN systems? Is there a reference or post with instructions on how to program NXDN systems on an SDS100? I have purchased, loaded, and validated the key for NXDN on my SDS100.