All hospitals on the southside have an assigned talkgroup on the 800 MHz TRS belonging to the city in which they are located. While the CHKD channel is located on the Norfolk 800 system, through mutual aid agreements other cities can switch to the Norfolk system when calling in reports. The same thing happens with Va Beach EMS units on the Leigh TG, or with Chesapeake medics that routinely transport to Maryview.
It isn't a crosspatch onto the Portsmouth system that you are hearing..the TG resides on the Norfolk system. Because of this, the TG is only listed under Norfolk.
On another interesting note...all Tidewater area 800 MHz fire-rescue radios have some ability to communicate on another city's system. Even Chesapeake, who was the first to go digital in the area, left some analog talkgroups to accomodate those agencies who had not yet upgraded to digital capable radios.
I hope this helps explain the setup with a little more detail.
Jason
Feed provider for Norfolk, Chesapeake and Portsmouth fire-rescue feeds.