Sorry for the late reply, if you were you using a hand held scanner having its own antenna & not a car roof top mag-stick antenna, the range is very limited for the Defect Detector radio calls. From what I had read, the DD site radios only have 1/10th the output power that the engine radios have (I had read those have from 45 to 50 Watts). In some places, the DD sites have even less power.
A couple of years ago, CSX had lowered the DD site's radio output power due to complaints from Chicago not wanting to hear them. I know this was done on the Grand Rapids sub-division & not sure if that was also done on the Plymouth sub, too. The DD at mp CH126.3 is in Clarksville, MI & the one at mp CH104.3 is Mulliken, MI.