What is a “subnet”?
Subnet is like the PL tone on your radio. For example, you and your buddies are doing a tornado chase. Members of the group can put “tornadochase” in the ‘Unproto’ field of the settings dialog. Then by entering the same string “tornadochase” in the ‘Subnet’ field of the filter dialog, you would filter for beacons of those members and see only their positions on the map.