Assuming RACOM...
My list jumps from 1619 to 1622, but i'm also in Des Moines so I'm at the mercy of units that drive thru the area (pretty rare). If you can, try to figure out what the channel might be named. Usually they will say "go to TAC" or "Unit A to Unit B on Ops". Sometimes they don't tho if the channel is meant for a SWAT team and they are the only ones that use it.
Nice find tho, I will add it to my list for GIDs to watch for!