Hmmm, I was under the impression that on the PSR-500 you could set a talkgroup to private, enter a specific Radio ID, and be able to listen to it. I base this on pages 40, 42, and 104 of the manual. Perhaps I am misunderstanding what it is saying.
Here is some of what the manual says.
HINT: TGRP objects are also used to receive Private/Individual Calls on
trunking systems that support these call types. Simply change the
Type: field from Group to Private. A Wildcard TGRP object with the
Type: field set to Private will monitor all Private/Individual Calls
seen on the system, or you can specify a radio ID to watch for in the
ID: field.
• Private Call with ID: will only monitor private call radio traffic
on the specified TGID (enter the desired Radio ID in the TGID
field, and set the Type field to Private)
ID
Type
Decimal, hex or AFS
depending on TSYS type
The digital address of the talkgroup or individual
radio ID on the trunked radio system.
Group or Private Use Group for talkgroup ID, Private for individual
radio ID.